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Yeast Extract (yeast + extract)
Selected AbstractsEthanol synthesis from glycerol by Escherichia coli redox mutants expressing adhE from Leuconostoc mesenteroidesJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2010P.I. Nikel Abstract Aims:, Analysis of the physiology and metabolism of Escherichia coli arcA and creC mutants expressing a bifunctional alcohol-acetaldehyde dehydrogenase from Leuconostoc mesenteroides growing on glycerol under oxygen-restricted conditions. The effect of an ldhA mutation and different growth medium modifications was also assessed. Methods and Results:, Expression of adhE in E. coli CT1061 [arcA creC(Con)] resulted in a 1·4-fold enhancement in ethanol synthesis. Significant amounts of lactate were produced during micro-oxic cultures and strain CT1061LE, in which fermentative lactate dehydrogenase was deleted, produced up to 6·5 ± 0·3 g l,1 ethanol in 48 h. Escherichia coli CT1061LE derivatives resistant to >25 g l,1 ethanol were obtained by metabolic evolution. Pyruvate and acetaldehyde addition significantly increased both biomass and ethanol concentrations, probably by overcoming acetyl-coenzyme A (CoA) shortage. Yeast extract also promoted growth and ethanol synthesis, and this positive effect was mainly attributable to its vitamin content. Two-stage bioreactor cultures were conducted in a minimal medium containing 100 ,g l,1 calcium d -pantothenate to evaluate oxic acetyl-CoA synthesis followed by a switch into fermentative conditions. Ethanol reached 15·4 ± 0·9 g l,1 with a volumetric productivity of 0·34 ± 0·02 g l,1 h,1. Conclusions:,Escherichia coli responded to adhE over-expression by funnelling carbon and reducing equivalents into a highly reduced metabolite, ethanol. Acetyl-CoA played a key role in micro-oxic ethanol synthesis and growth. Significance and Impact of the Study:, Insight into the micro-oxic metabolism of E. coli growing on glycerol is essential for the development of efficient industrial processes for reduced biochemicals production from this substrate, with special relevance to biofuels synthesis. [source] ISOLATION AND IDENTIFICATION OF A NOVEL ASPERGILLUS JAPONICUS JN19 PRODUCING ,-FRUCTOFURANOSIDASE AND CHARACTERIZATION OF THE ENZYMEJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2006LI-MEI WANG ABSTRACT A novel strain, Aspergillus sp. JN19, producing,-fructofuranosidase (FFase), was isolated from soil. According to the physiological and biochemical characteristics and its 18S rDNA gene sequence analysis, it was identified as Aspergillus japonicus. The optimal conditions for production of fructofuranosidase by A. japonicus JN-19 were investigated. The initial concentration of sucrose was 15 to 18%. Yeast extract was the best nitrogen source. K2HPO4 was effective in increasing enzyme production. The enzyme activity was increased to about 1.3 times by addition of 0.2% carboxymethylcellulose in the medium. The highest FFase activity was 55.42 U/mL at pH 5.5 and 30C, and production yield of fructooligosaccharides was 55.8%. Some characteristics of purified FFase were also studied. [source] Characterizing the regulation of the Pu promoter in Acinetobacter baylyi ADP1ENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Wei E. Huang Summary Effective gene trapping and screening requires sensory and regulatory compatibility of both host and exogenous systems. The naturally competent bacterium Acinetobacter baylyi ADP1 is able to efficiently take up and integrate exogenous DNA into the chromosome, making it an attractive host system for a wide range of metagenomic applications. To test the ability of A. baylyi ADP1 to express the XylR-regulated Pu promoter from Pseudomonas putida mt-2, we have constructed and examined an A. baylyi ADP1 strain, ADPWH- Pu-lux-xylR. The Pu promoter in ADPWH- Pu-lux-xylR was specifically induced by toluene, m -, p - and o- xylene. The substrate-induced Pu promoter was highly dependent on the growth medium: it was repressed in rich media until stationary phase, but was immediately induced in minimal medium with glucose as the sole carbon source (MMG). However, the Pu promoter was repressed in MMG when it was supplemented with 5 g l,1 yeast extract. Further investigation showed that the Pu promoter in MMG was repressed by 0.5 g l,1 aspartic acid or asparagine, but not repressed by glutamine. Changing the carbon/nitrogen ratios by addition of ammonia did not significantly affect the Pu promoter activity but addition of nitrate did. These results show that A. baylyi ADP1 reproduced characteristics of the XylR-regulated Pu promoter observed in its original host. It demonstrates that A. baylyi could provide an excellent genetic host for a wide range of functional metagenomic applications. [source] Impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH by Sclerotinia sclerotiorumFEMS MICROBIOLOGY LETTERS, Issue 1 2007Bryan J. Culbertson Abstract Sclerotinia sclerotiorum D-E7 was studied to determine the impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH in broth media (initial pH c. 5). Cultures with 0.1% nutritional supplement (tryptone, yeast extract, or soytone) yielded minimal growth, 2,3 mM oxalate, and a final culture pH of 4.2,4.8. In contrast, cultures with 0.1% nutritional supplement and 25 mM glucose yielded significant growth, minimal oxalate (<1 mM), and a final culture pH of 2.8,3.7. Similar trends were observed when glucose in 0.1% soytone cultures was replaced with 25 mM d -mannose, l -arabinose, or d -xylose. With 1% soytone-25 mM glucose cultures, growth and oxalate accumulation (,21 mM) occurred with little change in initial pH. This was not the case with 1% soytone-250 mM glucose cultures; increased glucose levels resulted in a decrease in oxalate accumulation (,7 mM) and in final culture pH (3.4). Time-course studies with these cultures revealed that oxalate accumulation was suppressed during growth when the culture pH dropped to <4. Overall, these results indicate that (1) the decrease in external pH (i.e. acidification) was independent of oxalate accumulation and (2) acidification coupled to glucose-dependent growth regulated oxalate accumulation by Sclerotinia sclerotiorum. [source] Isolation and characterization of a novel Bacillus sp., strain YAS1, capable of transforming tyrosol under hypersaline conditionsFEMS MICROBIOLOGY LETTERS, Issue 1 2005Slim Abdelkafi Abstract A moderately halotolerant, Gram-positive, aerobic, motile, spore-forming bacterium, designated as strain YAS1, was isolated from an olive-brine fermentation rich in aromatic compounds, after enrichment on tyrosol. Strain YAS1 grew between 25 and 45 °C and optimally at 37 °C. It grew in the presence of 0,15% (v/w) NaCl, with an optimum of 3,6% (v/w) NaCl. The DNA G + C content was found to be 49.9 mol%. Phylogenetic analysis of the 16S rRNA gene revealed that this isolate was a member of the genus Bacillus. The newly isolated strain YAS1 represents the first moderately halotolerant bacterium transforming tyrosol to p -hydroxyphenylacetic acid (PHPA) in the presence of yeast extract. [source] Nutrition influences growth and virulence of the insect-pathogenic fungus Metarhizium anisopliaeFEMS MICROBIOLOGY LETTERS, Issue 2 2005Farooq A. Shah Abstract Nutrition influenced growth, sporulation and virulence of the insect pathogenic fungus, Metarhizium anisopliae. Virulent conidia were produced on susceptible insect hosts, 1% yeast extract, 2% peptone, osmotic stress medium (OSM) and CN 10:1 medium. Several strain independent markers were identified that could be used to predict the virulence of M. anisopliae conidia. Virulent conidia typically had high levels of spore bound Pr1, an important cuticle degrading protease, and high germination rates. We also show for the first time that virulent conidia have an endogenous CN ratio below 5.2:1. Real Time PCR revealed that virulent conidia from insects contained significantly higher levels of transcripts of pr1 A and other pathogenicity-related genes than inoculum from artificial media. Of the artificial media studied, 1% yeast extract medium yielded the most virulent conidia, these had higher levels of transcripts of these pathogenicity-related genes than the least virulent conidia from the high conidia yielding CN 35:1 medium (= SDA), however, the levels were significantly lower than those in insect-derived conidia. Our study shows for the first time that the passaged inoculum is virulent irrespective of the original culture medium or insect host. Virulent conidia were consistently produced on OSM even though growth and sporulation were poor. We postulate that starvation conditions, whether in vivo or in vitro, results in de-repression of Pr1 and that elevated levels of this enzyme enhance fungal virulence. [source] Starch-like exopolysaccharide produced by the filamentous fungi Ophiostoma ulmi and O. novo-ulmiFOREST PATHOLOGY, Issue 2 2007R. Jeng Summary This paper describes the chemical and biochemical properties of exopolysaccharides (EPS) produced by Ophiostoma ulmi and O. novo-ulmi isolates, the Dutch elm disease (DED) fungi. Some of EPS have been considered as pathogenicity factor in the DED complex. The selected isolates grow well and produce EPS in a medium containing various types of carbon and nitrogen sources. EPS obtained from potato dextrose broth (PDB) medium appeared to be opaque, firm and stained purple blue with iodine-potassium iodide solution, whereas those from yeast extract (YE) medium were less opaque, jelly-like and remained unchanged in iodine solution. The selected fungal isolates produced much higher molecular weight EPS from the medium containing YE than from PDB. The results of this study suggest that high molecular weight compounds produced by O. ulmi (W9) and O. novo-ulmi (R136) are not involved in DED pathogenesis. Spectrometric analysis of acid-digested EPS obtained from PDB and YE revealed the presence of a monomer similar to glucose used as a standard. Thin layer chromatography indicated that glucan-1,4- , -glucosidase (glucoamylase) only hydrolyses EPS from PDB media and releases glucose. The results strongly indicate that isolates of O. ulmi and O. novo-ulmi produce starch-like EPS from PDB medium. The EPS obtained from YE medium lacked this characteristic. The biological significance and the potential use of these EPS are discussed. [source] Isolation and identification of Alicyclobacillus acidocaldarius by 16S rDNA from mango juice and concentrateINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2005Pieter A. Gouws Summary In this study we investigate the spoilage of ultra high temperature UHT mango juice as well as a carbonated fruit juice blend to identify organisms contributing to the spoilage. The mango concentrate, the final product, as well as the other ingredients used during manufacturing, were tested for the presence of Alicyclobacillus by polymerase chain reaction (PCR) and sequencing analyses. Microbiological examination of the mango pureé and spoiled fruit juices, using YSG agar [yeast extract 2 g, glucose 1 g, soluble starch 2 g, pH 3.7 (adjust with 2N H2SO4), H2O 1000 mL, bacto agar 15 g] incubated at 55 °C, detected sporeforming, acid dependent and thermotolerant bacteria. The hyper variable region of the 16S rDNA was amplified. The nucleotide sequence of the PCR fragments was determined using the ABI Prism 310 automated DNA sequencer and the collected sequencing data were analysed and compared with the non-redundant database using NCBI-BLAST. Alicyclobacillus acidocaldarius were isolated and identified by 16S rDNA gene sequences analyses. The results indicated that the mango purèe, as well as the final product of mango juice and the fruit juice blend, were positive for Alicyclobacillus. The preventative measures of low pH, pasteurization of mango juice and the subsequent use of aseptic packaging were not regarded as sufficient to prevent the outgrowth of Alicyclobacillus spoilage organisms. [source] The model of fungal population dynamics affected by nystatinINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2010Sergei I. Voychuk Abstract Fungal diseases are acute problems of the up-to-day medicine. Significant increase of resistance of microorganisms to the medically used antibiotics and a lack of new effective drugs follows in a growth of dosage of existing chemicals to solve the problem. Quite often such approach results in side effects on humans. Detailed study of fungi-antibiotic dynamics can identify new mechanisms and bring new ideas to overcome the microbial resistance with a lower dosage of antibiotics. In this study, the dynamics of the microbial population under antibiotic treatment was investigated. The effects of nystatin on the population of Saccharomyces cerevisiae yeasts were used as a model system. Nystatin effects were investigated both in liquid and solid media by viability tests. Dependence of nystatin action on osmotic gradient was evaluated in NaCl solutions. Influences of glucose and yeast extract were additionally analyzed. A "stepwise" pattern of the cell death caused by nystatin was the most intriguing. This pattern manifested in periodical changes of the stages of cell death against stages of resistance to the antibiotic. The mathematical model was proposed to describe cell-antibiotic interactions and nystatin viability effects in the liquid medium. The model implies that antibiotic ability to cause a cells death is significantly affected by the intracellular compounds, which came out of cells after their osmotic barriers were damaged © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and NulureJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2006W. L. Yee Abstract:, Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3,7 or 14,16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6,32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement. [source] The effect of carbon and nitrogen sources on bovicin HC5 production by Streptococcus bovis HC5JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009A.A.T. De Carvalho Abstract Aims:, To investigate the effect of media composition and agroindustrial residues on bovicin HC5 production by Streptococcus bovis HC5. Methods and Results:, Batch cultures of S. bovis HC5 were grown in basal medium containing different carbon and nitrogen sources. The activity of cell-free and cell-associated bovicin HC5 was determined in culture supernatants and acidic extracts obtained from cell pellets, respectively. Streptococcus bovis HC5 produced bovicin using a variety of carbon and nitrogen sources. The highest specific activity was obtained in media containing 16 g l,1 of glucose, after 16 h of incubation. The peak in cell-free and cell-associated bovicin HC5 activity was detected when S. bovis HC5 cultures reached stationary phase. The bovicin HC5 specific activity and bacterial cell mass increased approximately 3-fold when yeast extract and trypticase (0·5 and 1·0 g l,1, respectively) were added together to the basal medium. Streptococcus bovis HC5 cultures produced bovicin HC5 in cheese whey and sugar cane juice and maximal volumetric productivity was obtained after 12 h of incubation. Conclusions:,Streptococcus bovis HC5 is a versatile lactic acid bacterium that can utilize several carbon and nitrogen sources for bovicin HC5 production. This bacterium could be a useful model to study bacteriocin production in the rumen ecosystem. Significance and Impact of the Study:, The use of agroindustrial residues as carbon sources could have an economical impact on bovicin HC5 production. To our knowledge, this is the first report to show the use of sugar cane juice for bacteriocin production by lactic acid bacteria. [source] Optimization of a medium for enhancing nicotine biodegradation by Ochrobactrum intermedium DN2JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2006Y.J. Yuan Abstract Aims:, To optimize a medium for nicotine degradation by Ochrobactrum intermedium DN2 in presence of yeast extract, glucose and Tween 80 using response surface methodology (RSM). Methods and Results:, In this study, the effects of yeast extract, glucose and Tween 80 on nicotine degradation were investigated in flasks using a novel nicotine-degrading bacterium, O. intermedium DN2. A full factorial central composite design was applied in the design of experiments and in the analysis of the experimental data. The results showed that the most significant variable influencing nicotine degradation was yeast extract, followed by glucose, and then Tween 80. Moreover these three factors interacted with each other and combined to produce positive effects on nicotine degradation. The experimental data also allowed the development of an empirical model (P < 0·0001) describing the inter-relationship between independent and dependent variables. By solving the regression equation, the optimal values of the variables were determined as: yeast extracts 0·094%, glucose 0·101% and Tween 80 0·080%. Using the medium obtained, about 1220 mg l,1 of nicotine was degraded (95·55%) within 10 h at the specific biodegradation of 116·59 mg l,1 h,1 in 30-l bioreactor containing 25-l tobacco extract. Conclusions:, An optimal medium of nicotine degradation by the strain DN2 was obtained. Significance and Impact of the Study:, RSM proved to be reliable in developing the model, optimizing factors and analysing interaction effects. The results provide better understanding on the interactions between yeast extract, glucose and Tween 80 for nicotine biodegradation. [source] Mycelium cultivation, chemical composition and antitumour activity of a Tolypocladium sp. fungus isolated from wild Cordyceps sinensisJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006P.H. Leung Abstract Aims:, To examine and illustrate the morphological characteristics and growth kinetics of Cs-HK1, a Tolypocladium fungus, isolated from wild Cordyceps sinensis in solid and liquid cultures, and the major chemical constituents and antitumour effects of Cs-HK1 mycelium. Methods and Results:, The Cs-HK1 fungus was isolated from the fruiting body of a wild C. sinensis and identified as a Tolypocladium sp. fungus. It grew rapidly at 22,25°C on a liquid medium containing glucose, yeast extract, peptone and major inorganic salts, with a specific growth rate of 1·1 day,1, reaching a cell density of 23·0 g dw l,1 in 7,9 days. Exopolysaccharides accumulated in the liquid culture to about 0·3 g l,1 glucose equivalent. In comparison with natural C. sinensis, the fungal mycelium had similar contents of protein (11·7,,g) and carbohydrate (654·6,,g) but much higher contents of polysaccharide (244·2 mg vs 129·5 mg), adenosine (1116·8,,g vs 264·6 ,g) and cordycepin (65·7 ,g vs 20·8 ,g) (per gram dry weight). Cyclosporin A, an antibiotic commonly produced by Tolypocladium sp., was also detected from the mycelium extract. The hot water extract of mycelium showed low cytotoxic effect on B16 melanoma cells in culture (about 25% inhibition) but significant antitumour effect in animal tests, causing 50% inhibition of B16 cell-induced tumour growth in mice. Conclusions:, The Tolypocladium sp. fungus, Cs-HK1, can be easily cultivated by liquid fermentation. The mycelium biomass contained the major bioactive compounds of C. sinensis, and the mycelium extract had significant antitumour activity. Significance and Impact of the Study:, The Cs-HK1 fungus may be a new and promising medicinal fungus and an effective and economical substitute of the wild C. sinensis for health care. [source] Flocculation onset in Saccharomyces cerevisiae: the role of nutrientsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2005S. Sampermans Abstract Aims:, To examine the role of the nutrients on the onset of flocculation in an ale-brewing strain, Saccharomyces cerevisiae NCYC 1195. Methods and Results:, Flocculation was evaluated using the method of Soares, E.V. and Vroman, A. [Journal of Applied Microbiology (2003) 95, 325]. For cells grown in chemically defined medium (yeast nitrogen base with glucose) or in rich medium (containing yeast extract, peptone and fermentable sugars: fructose or maltose), the onset of flocculation occurred after the end of exponential respiro-fermentative phase of growth being coincident with the attainment of the lower level of carbon source in the culture medium. Cells, in exponential respiro-fermentative phase of growth, transferred to a glucose-containing medium without nitrogen source, developed a flocculent phenotype, while these carbon source starved cells, in the presence of all other nutrients that support growth, did not flocculate. In addition, cells in exponential phase of growth, under catabolite repression, when transferred to a medium containing 0·2% (w/v) of fermentable sugar (fructose or maltose) or 2% (v/v) ethanol, showed a rapid triggering of flocculation, while when incubated in 2% (v/v) glycerol did not develop a flocculent phenotype. Conclusions:, The onset of flocculation occurs when a low sugar and/or nitrogen concentration is reached in culture media. The triggering of flocculation is an energetic dependent process influenced by the carbon source metabolism. The presence of external nitrogen source is not necessary for developing a flocculent phenotype. Significance and Impact of the Study:, This work contributes to the elucidation of the role of nutrients on the onset of flocculation in NewFlo phenotype yeast strains. This information might be useful to the brewing industry, in the control of yeast flocculation, as the time when the onset of flocculation occurs can determine the fermentation performance and the beer quality. [source] Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimizationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2010Kata Hetényi Abstract BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B-vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen-containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L,1 h,1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro-elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry [source] Fermentation of glucose and starch particles using an inexpensive mediumJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2010Nancy Bawa Abstract BACKGROUND: In North America, compared with sugar, starch is a more economical raw material to produce ethanol. Recently low temperature processing of starch granules directly to ethanol has been commercialized. With a view to minimizing process costs while maintaining a satisfactory ethanol yield, an inexpensive medium that does not require the addition of commercial ,-amylase has been developed for low temperature, direct fermentation of starch particles. RESULTS: Compared with an expensive medium that contained both yeast extract and ,-amylase, the inexpensive medium resulted in identical and 10% higher ethanol yields using glucose and starch granules as the raw substrates, respectively, but required longer processing times. Based on the different ingredient prices for expensive and inexpensive media, the operating cost to produce 10 million litres per year of ethanol utilizing simultaneous raw starch hydrolysis and fermentation is reduced over $ 2 million (Cdn) per year when using inexpensive medium. CONCLUSION: The new inexpensive medium and simultaneous raw starch hydrolysis and fermentation is considered the best strategy to produce ethanol directly from starch particles in North America. Copyright © 2009 Society of Chemical Industry [source] Processing of ethanol fermentation broths by Candida krusei to separate bioethanol by pervaporation using silicone rubber-coated silicalite membranesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2009Toru Ikegami Abstract BACKGROUND: Pervaporation employing ethanol-permselective silicalite membranes as an alternative to distillation is a promising approach for refining low-concentration bioethanol solutions. However, to make the separation process practicable, it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separation process. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as the influence of several fermentation broth nutrient components. RESULTS:Candida krusei IA-1 produces an extremely low level of succinate. The decrease in permeate ethanol concentration through a silicone rubber-coated silicalite membrane during the separation of low-succinate C. krusei IA-1 fermentation broth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating the fermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water. The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% before the addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect on pervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA-1 fermentation broth by pervaporation, it is useful to treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary to suppress the accumulation of glycerol. Copyright © 2009 Society of Chemical Industry [source] Fermentative production of L(+)-lactic acid from starch hydrolyzate and corn steep liquor as inexpensive nutrients by batch culture of Enterococcus faecalis RKY1JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2008Young-Jung Wee Abstract BACKGROUND: Attempts were made to determine the lactic acid production efficiency of novel isolate, Enterococcus faecalis RKY1 using four different starches (corn, tapioca, potato, and wheat starch) with different concentrations (50, 75, 100, and 125 g L,1) and corn steep liquor as an inexpensive nitrogen source. RESULTS: The yield of lactic acid from each starch was higher than 95% based on initial starch concentrations. High lactic acid concentration (129.9 g L,1) and yield (1.04 g-lactic acid g,1 -starch) were achieved faster (84 h) from 125 g L,1 of corn starch. Among the starches used, tapioca starch fermentation usually completed in a shorter incubation period. The final dry cell weight was highest (7.0 g L,1) for the medium containing 75 g L,1 of corn starch, which resulted in maximum volumetric productivity of lactic acid (3.6 g L,1 h,1). The addition of 30 g L,1 corn steep liquor supplemented with a minimal amount of yeast extract supported both cell growth and lactic acid fermentation. CONCLUSION:Enterococcus faecalis RKY1 was found to be capable of growing well on inexpensive nutrients and producing maximum lactic acid from starches and corn steep liquor as lower-cost raw materials than conventionally-used refined sugars such as glucose, and yeast extract as an organic nitrogen source in laboratory-scale studies. These fermentation characteristics are prerequisites for the industrial scale production of lactic acid. Copyright © 2008 Society of Chemical Industry [source] Optimization of growth medium for the production of ,-amylase from Bacillus amyloliquefaciens using response surface methodologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2006M Saban Tanyildizi Abstract The optimization of nutrient levels for the production of ,-amylase by Bacillus amyloliquefaciens was carried out using response surface methodology (RSM) based on the 23 factorial central composite design (CCD). This procedure limited the number of actual experiments performed while allowing for possible interactions between three components. RSM was adopted to derive a statistical model for the effect of starch, peptone and yeast extract (YE) on ,-amylase production. The P -value of the coefficient for linear effects of starch and YE concentration was <0.0001, suggesting that this was the principal experimental variable, having the greatest effect on the production of ,-amylase. The optimal combinations of media constituents for maximum ,-amylase production were determined as 12.61 g L,1 starch, 2.83 g L,1 peptone and 1.25 g L,1 YE. The optimization of the medium resulted not only in a 34% higher enzyme activity than unoptimized medium but also in a reduced amount of the required medium constituents. Copyright © 2006 Society of Chemical Industry [source] Experimentation of a new mode of batch culture for lactic acid bacteria: cell reuse with an initial period of cell reactivation at acidic pHJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2001Abdeltif Amrane Abstract Cell reuse was compared with conventional batch culture for lactic acid fermentation, the objective was to simplify the batch process and to alleviate the need for added nitrogen. At high levels of nitrogen supplementation to the culture medium (20,g,dm,3 yeast extract and 5,g,dm,3 each of tryptic and pancreatic casein peptones), similar mean production rates were obtained with partial cell reuse and the conventional batch process, without any additional gain when cells were initially reactivated at acidic pH. On the other hand, cell reuse with an initial period without pH control appeared particularly effective for low levels of nitrogen supplementation (5,g,dm,3 yeast extract): a 57% increase in the mean production rate with regard to the conventional batch process was obtained. © 2001 Society of Chemical Industry [source] Optimization of Medium Composition for Nisin Fermentation with Response Surface MethodologyJOURNAL OF FOOD SCIENCE, Issue 6 2008X.-X. Zhou ABSTRACT:, Nisin is an effective food biopreservative widely used in food industry. However, 1 problem of concern is limited production rate and final nisin concentration. A nisin-producing strain, L. lactis Lac2, a mutant strain with high yield of nisin, was obtained in our laboratory recently. In the present study, a fractional factorial design was applied to investigate the main factors that affect the yield of L. lactis Lac2. Central composite experimental design and response surface methodology were adopted to derive a statistical model for optimizing the composition of the medium. The results showed that the optimum medium for nisin production of L. lactis Lac2 was composed of 2.68% sucrose (w/v), 0.5% tryptone (w/v), 1% yeast extract (w/v), 0.3% Tween-80 (w/v), 0.02% MgSO4·7H2O (w/v), 0.81% NaCl (w/v), 1.91% K2HPO4 (w/v), 0.05% ascorbic acid (w/v), and 2% agar (w/v) (if necessary) at pH 6.5. When cultured in the optimum medium, the nisin yield is an average of 3381.81 IU/mL, which nearly doubled the yield when incubated in the initial medium. Also, the concentration of tryptone was decreased while that of the sucrose was increased when compared with CM broth, which means a reduction of the fermentation cost. [source] Comparison of the performances of different fermentation strategies on cell growth and bacteriocin production by Lactobacillus curvatus CWBI-B28JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2007Hakim Ghalfi Abstract The dynamics of cell growth and bacteriocin production by Lactobacillus curvatus CWBI-B28 in modified De Man/Rogosa/Sharp (mMRS) broth with various concentrations of glucose and complex nitrogen source (CNS; peptone, yeast extract and meat extract) was investigated in flask fermentations and in a laboratory fermentor using batch and fed-batch cultivations. In fed-batch fermentation the rate of feeding of the reactor with the substrates was either maintained constant (0.12 L h,1) or varied exponentially as a function of time. The results showed that both cell growth and bacteriocin activity were influenced by changes in the concentrations of glucose and CNS. Optimal growth and bacteriocin activity were obtained in mMRS broth containing 40 g L,1 glucose and 40 g L,1 CNS (mMRS40/40). A bacteriocin titre of 4266 AU mL,1 and a cell count of 8.7 log colony-forming units (cfu) mL,1 were recorded when this medium was used for cultivation. In batch fermentation using the same medium, a higher cell count (9.5 log cfu mL,1) and twice as much bacteriocin as in flask fermentation were produced. The highest bacteriocin titre (8533 AU mL,1) was obtained with fed-batch fermentation at an exponentially varying rate of feeding. Bacteriocin activity and cell dry mass did not always correlate. Copyright © 2007 Society of Chemical Industry [source] Colonization of Legionella Species in Hotel Water Systems in TurkeyJOURNAL OF TRAVEL MEDICINE, Issue 6 2007Haluk Erdogan MD Background The goal of this study was to evaluate the prevalence of Legionella species in hotel water distribution systems in Alanya, Turkey, which is an important tourism center. Methods Water and swab samples were obtained from 52 Turkish hotels from August 2003 to September 2005. Water samples were collected in 100 mL sterile containers and were concentrated by membrane filters with a pore size of 0.45 ,m. Heat treatment was used to eliminate other microorganisms from the samples, which were then spread on buffered charcoal yeast extract , agar plates and glycine, vancomycin, polymyxin, cycloheximide agar plates. Cysteine-dependent colonies were identified by latex agglutination. Results In all, 491 water and swab samples were analyzed. The results of all samples were negative for Legionella in 16 (30.8%) hotels. Legionella species (92.5% of which were Legionella pneumophila) were detected in 93 (18.9%) of the samples. The most frequently isolated species were L pneumophila serogroups 6 (63.5%) and 1 (21.5%). ConclusionsLegionella pneumophila serogroup 6 was the most common isolate detected in Turkish hotel water systems in our study. The result of Legionella urinary antigen tests, which are the diagnostic tests most often used to identify legionnaires' disease, may be negative in people infected with L pneumophila serogroup 6. We suggest that clinicians should apply the whole spectrum of laboratory methods for the detection of legionnaires' disease in patients with pneumonia of unknown origin and history of travel to Alanya, Turkey. [source] Efficacy of sodium hypochlorite and peracetic acid in sanitizing green coconutsLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2009E.H.M. Walter Abstract Aims:, To evaluate the efficacy of sanitizing green coconuts (Cocos nucifera L.) through the treatment applied by juice industries using sodium hypochlorite and peracetic acid. Methods and Results:, The surface of the fruits was inoculated with a mixture of five Listeria monocytogenes strains. The treatments consisted in immersing the fruits for 2 min at room temperature in sodium hypochlorite solution containing 200 mg l,1 residual chlorine at pH 6·5, and 80 mg l,1 solution of peracetic acid or sterile water. Bacterial populations were quantified by culturing on trypticase soy agar supplemented with yeast extract and Oxford selective culture medium; however, recovery was higher on the nonselective medium. Immersion in water produced a reduction in the L. monocytogenes population of 1·7 log10 CFU per fruit, while immersion in sodium hypochlorite and peracetic acid solutions resulted in population reductions of 2·7 and 4·7 log10 CFU per fruit respectively. Conclusions:, The treatments studied are efficient to green coconuts. Significance and Impact of the Study:, Sanitation of green coconut is one of the most important control measures to prevent the contamination of coconut water. This article provides information that shows the adequacy of sanitizing treatments applied by the juice industries. [source] Modification of culture conditions for production of the anti-tubercular hirsutellones by the insect pathogenic fungus Hirsutella nivea BCC 2594LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2008S. Madla Abstract Aims:, This work aimed to improve the production of anti-tubercular hirsutellones by the insect pathogenic fungus Hirsutella nivea BCC 2594. Methods and Results:, The fungus was cultivated under different carbon/nitrogen sources and aerations (shake vs static flasks) to improve the production of the anti-tubercular alkaloids, hirsutellones A,D. Under the basal conditions, static cultivation at 25°C in minimum salt medium, only hirsutellone B and C were detected with maximum concentrations of 139·00 and 18·27 mg l,1. Substitution of fructose for glucose and peptone for yeast extract increased the titres of hirsutellones A, B and C about two- to threefold. However, hirsutellone D was not detected in this medium. Culture agitation induced the production of hirsutellone D. As a result, the significant amounts of hirsutellones A,D were obtained with the concentration of 29·93, 169·63, 22·65 and 15·71 mg l,1 within 15 days. Conclusions:, Improved titres of hirsutellones in H. nivea BCC 2549 were achieved with an agitated (200 rev min,1) fructose,peptone medium at 25°C. Significance and Impact of the Study:, Improved yields of hirsutellones B,D will enable medicinal chemistry modifications leading to a development of a potential candidate for tuberculosis therapy. [source] Accumulation of arsenic by Traustochytrium sp.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2002CHN-1 from Seto Inland Sea Abstract The accumulation of arsenic by Traustochytrium sp. CHN-1 (Labyrinthulids) was examined by using a medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone in a half salt concentration of sea water] containing arsenic as As(V), As(III). Traustochytrium sp. CHN-1 was grown in 1/2 sea water medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone] containing an arsenate (As(V)) at up to 1000,mg dm,3 and arsenite (As(III)) at up to 50,mg dm3. The cells died even at [As(III)]-100,mg dm,3. These results suggested that the order of growth inhibition of Traustochytrium sp. CHN-1 by arsenic was As(III),>,As(V). The biomass of Traustochytrium sp. CHN-1 decreased with an increase of the surrounding arsenic concentration. On the other hand, the arsenic concentration in cells increased with an increase of the surrounding arsenic concentration. Arsenic compounds were extracted with methanol/water (1:1) from a freeze-dried sample of Traustochytrium sp. CHN-1. The extracts were analyzed by high-performance liquid chromatography, with an inductively coupled plasma mass spectrometer serving as an arsenic-specific detector. Arsenite, arsenate, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) and arsenosugar were identified in Traustochytrium sp. CHN-1. The order of arsenic species in Traustochytrium sp. CHN-1 was As(V),>,DMAA,>,As(III),>,MMAA,>,arsenosugar at [As]-10,mg dm,3 in the medium. Detoxification of arsenic by cells was probably achieved by methylation. Copyright © 2002 John Wiley & Sons, Ltd. [source] Haematological modulation and growth of Labeo rohita fingerlings: effect of dietary mannan oligosaccharide, yeast extract, protein hydrolysate and chlorellaAQUACULTURE RESEARCH, Issue 1 2009Simi Rose Andrews Abstract The present study was conducted for 60 days to delineate the efficacy of various dietary immunomodulators like mannan oligosaccharide (MOS), yeast extract (YE), protein hydrolysate (PH) and chlorella (CL) in Labeo rohita fingerlings. Five hundred and eighty-five L. rohita fingerlings (average weight: 4.15 ± 0.07 g) were randomly distributed in 13 treatment groups with each of three replicates. Thirteen semi-purified isonitrogenous (crude protein 324.7,332.5 g kg,1) and isocaloric (17.66,17.80 MJ kg,1) diets were prepared with three graded levels (1%, 2% or 4%) of immunostimulants, except the control. At the end of the feeding trial, weight gain%, specific growth rate, feed conversion ratio, leucocyte count, erythrocyte count, haemoglobin content, serum protein, globulin, albumin,globulin ratio, nitroblue tetrazolium (NBT) value and survival percentage were evaluated. Growth was significantly higher in the MOS-fed group. All the immune parameters studied were also recorded higher in the MOS 1%-supplemented group. The survival percentage after challenging with Aeromonas hydrophila was higher (P<0.05) in the MOS-, YE- and PH-fed groups and the lowest in the CL-treated group. It can be concluded that dietary supplementation of MOS at a 1% dietary level promotes growth and survival in L. rohita fingerlings. In contrast, higher inclusion levels of immunostimulants led to an immunosuppressive effect in L. rohita fingerlings. [source] Parameter oscillation attenuation and mechanism exploration for continuous VHG ethanol fermentationBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009F.W. Bai Abstract A bioreactor system composed of a stirred tank and three tubular bioreactors in series was established, and continuous ethanol fermentation was carried out using a general Saccharomyces cerevisiae strain and a very high gravity medium containing 280 g,L,1 glucose, supplemented with 5 g,L,1 yeast extract and 3 g,L,1 peptone. Sustainable oscillations of glucose, ethanol, and biomass were observed when the tank was operated at the dilution rate of 0.027 h,1, which significantly affected ethanol fermentation performance of the system. After the tubular bioreactors were packed with 1/2, Intalox ceramic saddles, the oscillations were attenuated and quasi-steady states were achieved. Residence time distributions were studied for the packed bioreactors by the step input response technique using xylose as a tracer, which was added into the medium at a concentration of 20 g,L,1, indicating that the backmixing alleviation assumed for the packed tubular bioreactors could not be established, and its contribution to the oscillation attenuation could not be verified. Furthermore, the role of the packing's yeast cell immobilization in the oscillation attenuation was investigated by packing the tubular bioreactors with packings with significant difference in yeast cell immobilization effects, and the experimental results revealed that only the Intalox ceramic saddles and wood chips with moderate yeast cell immobilization effects could attenuate the oscillations, and correspondingly, improved the ethanol fermentation performance of the system, while the porous polyurethane particles with good yeast cell immobilization effect could not. And the viability analysis for the immobilized yeast cells illustrated that the extremely lower yeast cell viability within the tubular bioreactors packed with the porous polyurethane particles could be the reason for their inefficiency, while the yeast cells loosely immobilized onto the surfaces of the Intalox ceramic saddles and wood chips could be renewed during the fermentation, guaranteeing their viability and making them more efficient in attenuating the oscillations. The packing Raschig rings without yeast cell immobilization effect did not affect the oscillatory behavior of the tubular bioreactors, further supporting the role of the yeast cell immobilization in the oscillation attenuation. Biotechnol. Bioeng. 2009;102: 113,121. © 2008 Wiley Periodicals, Inc. [source] Biomass recycling from a riboflavin cultivation with B. subtilis: Lysis, extract production and testing as substrate in riboflavin cultivationBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2006Karlheinz Bretz Abstract Autolysis of riboflavin-producing B. subtilis can be induced by pH, lack of carbon source, and the buffer system. Stress factors like temperature shift or oxygen dearth enhance the autolysis process. After cultivation of a riboflavin-producing strain, the pH of the whole culture broth was adjusted to 6.5,7.5. At a temperature of 40°C, autolysis started after 1 h. Adding a defined amount of commercially available endo- and exo-proteases enhanced both auto- and proteo-lysis. Optimization of endo- and exo-protease concentrations and of the time increased the degree of proteolysis. Additionally, the amount of DNA and Protein trapped in the riboflavin crystals could be significantly reduced by autolysis. After autolysis, the cultivation broth was centrifuged and the supernatant was cross-flow filtrated with a cut off of 10 kDa. Using this autolysate instead of yeast extract as a medium component for riboflavin production with B. subtilis, a riboflavin yield of 77% was obtained in comparison with the standard cultivation on yeast extract. © 2006 Wiley Periodicals, Inc. [source] Effect of yeast extract on speciation and bioavailability of nickel and cobalt in anaerobic bioreactorsBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2003G. Gonzalez-Gil Abstract The speciation of metals plays an important role in their bioavailability. In the case of anaerobic reactors for the treatment of wastewaters, the ubiquitous presence of sulfide leads to extensive precipitation of metals like nickel and cobalt, which are essential for the metabolism of the anaerobic microorganisms that carry out the mineralization of the pollutants present in the wastewater. In practice, nickel, cobalt, and iron are added in excessive amounts to full-scale installations. This study is concerned with the complexation of nickel and cobalt with yeast extract and its effect on the biogas production by methanogenic biomass. Adsorptive stripping voltammetry (AdSV) was used to get information about the stability and complexing capacity of the metal,yeast extract complexes formed. Nickel and cobalt form relatively strong organic complexes with yeast extract. The bioavailability of these essential metals in anaerobic batch reactors was dramatically increased by the addition of yeast extract. This is due to the formation of dissolved bioavailable complexes, which favors the dissolution of metals from their sulfides. Trace doses of yeast extract may be effective in keeping additions of essential metals to anaerobic reactors at a minimum. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 134,142, 2003. [source] | ||||||||||||||||||||||||||||