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Acid Production (acid + production)
Kinds of Acid Production Selected AbstractsA NEW METHOD FOR ELLAGIC ACID PRODUCTION FROM POMEGRANATE HUSKJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2008JINGJING LU ABSTRACT Pomegranate (Punica granatum L.) husk, a by-product of the pomegranate juice industry, is an inexpensive and abundant source of ellagic acid. Ellagic acid is widely used as functional food for its physiological functions. It is the breakdown product of ellagitannins. To date, the preparation of ellagic acid from pomegranate husk has not been reported. This article reports a new process for ellagic acid production from pomegranate husk by extraction of tannins followed by acid hydrolysis and purification by extraction and recrystallization. Several tests were conducted to obtain optimum conditions including extraction of tannins by varying solvents, acid concentration and reaction time for acid hydrolysis and the volume of methanol used for purification. Ellagic acid (3.5 g) with 90% purity from 100 g pomegranate husk was obtained. This new method is easy to scale up. All equipment used in this production process is widely used in food processing industry. The cost of production is low. It is suitable for industrial applications. PRACTICAL APPLICATIONS The production of ellagic acid is easier and the yield and purity of ellagic acid produced this way are higher than before. This method can be used not only for experiment in laboratory but also for industrial applications. The material , pomegranate husk , is a by-product of the pomegranate juice industry, so it is very cheap and easy to get. High-purity ellagic acid produced this way is sold to many companies back home and abroad. It is used as food additive and cosmetic material because of its antioxidant activity and whiteningfunction. The toxicity of pomegranate husk is lower than that of gallnut, which has been the main material of ellagic acid production in the past. Reagents are common and inexpensive; some of them are reusable. [source] EFFECT OF PHYSICAL FACTORS ON ACETIC ACID PRODUCTION IN BRETTANOMYCES STRAINSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2005C. CASTRO-MARTINEZ ABSTRACT Four species of Brettanomyces (intermedius, bruxellensis, custersianus, clausenii) were examined to ascertain their acetic acid production capacity. The results showed that B. bruxellensis was the strain with the best volumetric productivity ,and ,specific ,production ,rate ,(P = 0.065 gL,1 h,1; ,Vp = 0.43 gg,1h,1). The best kinetic parameters were reached (P = 0.133 gL,1 h,1; Yp/s = 0.23; Pmax = 11.64 gL,1) ,at ,an ,airflow ,of ,288 Lh,1,(0.6 vvm, ,OTR = 124 mgO2L,1,h,1), and substrate inhibition was not observed. The influence of temperature and agitation on acetic acid production by B. bruxellensis in a glucose medium was investigated at different levels, 26, 30, 34C and 250, 350, 450 rpm, respectively. Temperature and agitation were shown to be deci-sive factors (P < 0.05) in acetic acid production at 288 Lh,1(0.6 vvm, OTR = 124 mgO2L,1 h). The optimal conditions for a high volumetric productivity were 30C and 250 rpm, respectively. [source] IDENTIFICATION AND ASSESSMENT OF DOMOIC ACID PRODUCTION IN OCEANIC PSEUDO-NITZSCHIA (BACILLARIOPHYCEAE) FROM IRON-LIMITED WATERS IN THE NORTHEAST SUBARCTIC PACIFIC,JOURNAL OF PHYCOLOGY, Issue 3 2008Adrian Marchetti We identified and investigated the potential toxicity of oceanic Pseudo-nitzschia species from Ocean Station Papa (OSP), located in a high-nitrate, low-chlorophyll (HNLC) region of the northeast (NE) subarctic Pacific Ocean. Despite their relatively low abundances in the indigenous phytoplankton assemblage, Pseudo-nitzschia species richness is high. The morphometric characteristics of five oceanic Pseudo-nitzschia isolates from at least four species are described using SEM and TEM. The species identified are Pseudo-nitzschia dolorosa Lundholm et Moestrup, P. granii Hasle, P. heimii Manguin, and P. cf. turgidula (Hust.) Hasle. Additional support for the taxonomic classifications based on frustule morphology is provided through the sequencing of the internal transcribed spacer 1 (ITS1) rDNA. Pseudo-nitzschia species identification was also assessed by the construction of ITS1 clone libraries and using automated ribosomal intergenic spacer analysis (ARISA) for environmental samples collected during the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES), conducted in close proximity to OSP in July of 2002. Based on ITS1 sequences, the presence of P. granii, P. heimii, P. cf. turgidula, and at least five other putative, unidentified Pseudo-nitzschia ITS1 variants was confirmed within iron-enriched phytoplankton assemblages at OSP. None of the oceanic isolates produced detectable levels of particulate domoic acid (DA) when in prolonged stationary phase due to silicic acid starvation. The lack of detectable concentrations of DA suggests that either these strains produce very little or no toxin, or that the physiological conditions required to promote particulate DA production were not met and thus differ from their coastal, toxigenic congeners. [source] DOMOIC ACID PRODUCTION By PSEUDO-NITZSCHIA SERIATA (BACILLARIOPHYCEAE) IN SCOTTISH WATERS,JOURNAL OF PHYCOLOGY, Issue 4 2004Johanna Fehling In 1999, a 49,000 km2 area in western Scottish waters was closed to shellfish harvesting due to the amnesic shellfish poisoning (ASP) toxin domoic acid (DA). The only previously confirmed DA producer identified had been Pseudo-nitzschia australis Frenguelli. The toxin has appeared every year since and has led to more harvesting closures. We isolated and cultured two strains of Pseudo-nitzschia seriata f. seriata (P. T. Cleve) H. Peragallo from western Scottish waters in 2001 and 2002. They were identified using TEM analysis of their morphological fine structure and sequencing of the internal transcribed spacer (ITS)1, 5.8S, ITS2, and partial large subunit (LSU) rDNA. The morphology of the Scottish P. seriata f. seriata strains differed slightly, for example, in the number of poroid rows, from descriptions in identification keys. Comparison of P. seriata sequences with those of two co-occurring Pseudo-nitzschia australis isolates showed an overall divergence of only 0.012. Sequence divergence between both species was highest in the ITS1 region (0.036). Combined morphological and genetic approaches are needed to identify closely related Pseudo-nitzschia species. The P. seriata strains grew successfully at 15°C, suggesting that although seen as a psychrophilic species, it may also occur at higher water temperatures. All isolates produced DA in stationary phase (measured on day 25): 0.16,0.23 pg DA·cell,1 in P. seriata and 0.15,1.68 pg DA·cell,1 in P. australis. Our study is the first to identify P. seriata f. seriata as a DA producer in Scottish waters and indicates that at least it and P. australis can be responsible for ASP toxicity in that region. [source] Effects of Linoleic Acid on Conjugated Linoleic Acid Production by Planktonic Rumen Bacteria from Grain-fed CowsJOURNAL OF FOOD SCIENCE, Issue 5 2003Y. J. Kim ABSTRACT Ruminal conjugated linoleic acid (CLA) production from linoleic acid (LA) was characterized in vitro. Rumen bacteria from grain-fed cows were more active in BH than those from hay-fed cows. Particleassociated bacteria produced more hydrogenated products leaving less CLA than the planktonic bacteria (P < 0.05). CLA production by planktonic bacteria did not always correlate to LA given; longer incubations generally decreased CLA concentration and increased c9, t11/t10, c12 ratio, especially at higher LA concentrations. The preincubated cells to LA produced more CLA than the unexposed ones and the increase was more evident with c9, t11 CLA (P < 0.05). This study provides insight into how cattle diet and LA feedings affect ruminal CLA production. [source] Extract of Juglandaceae regia Inhibits Growth, In-vitro Adherence, Acid Production and Aggregation of Streptococcus mutansJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2000A. G. JAGTAP Aqueous and alcoholic extracts from Juglandaceae regia, used as chewing sticks to maintain oral hygiene, were tested for their ability to inhibit the growth and some physiological functions of Streptococcus mutans. Both the aqueous and the alcoholic extract strongly inhibited the growth, in-vitro adherence, acid production and glucan-induced aggregation of S. mutans. At a concentration of 8% w/v, the aqueous extract produced a 95% inhibition (P < 0.05) of adherence of S. mutans to glass and a 40% inhibition (P < 0.05) of adherence to tooth surface. The alcoholic extract at a concentration of 10% w/v produced a 95% inhibition (P < 0.05) of adherence of S. mutans to glass and a 56% inhibition (P < 0.05) of adherence to tooth surface. At concentrations of 2% w/v the aqueous and alcoholic extracts significantly inhibited (P < 0.05) glucan-induced aggregation of S. mutans and the in-vitro salivary glycolytic reaction for up to 5 h. Bactericidal effects on S. mutans were also evident. At a concentration of 10% w/v, the zone of inhibition observed with the aqueous extract was 12 ± 0.01 mm and that observed with the alcoholic extract was 12.6 ± 0.02 mm. As the in-vitro studies had shown that both the aqueous and the alcoholic extract of J. regia, at concentrations of 10% w/v, could inhibit the growth as well as the acid-producing ability of S. mutans, they were tested at the same concentration for their activity in-vivo. Three subjects were employed. Parameters monitored were salivary bacterial count and salivary glycolysis. Mouth-rinsing with the aqueous but not the alcoholic extract significantly reduced total streptococcal counts in the salivary samples obtained up to, and including, 3 h after rinsing, compared with the counts obtained pre-rinsing or after placebo rinsing. Mouth-rinsing with the aqueous extract produced a 65%, 27% and 78% reduction (P < 0.05) in the streptococcal count in the salivary samples obtained 10 min, 1 h and 3 h after rinsing, respectively. Both the aqueous and the alcoholic extract also inhibited the glycolytic reaction by the salivary bacteria for up to 90 min post-rinsing. This study provides evidence to justify the use of J. regia sticks as an aid to maintain oral hygiene. [source] Sensitivity to Hydrogen Peroxide of Growth and Hyaluronic Acid Production by Streptococcus zooepidemicus ATCC 39920ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005M.D. Mashitah Abstract The sensitivity to hydrogen peroxide (H2O2) of growth and hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 was studied under various conditions. In sheep blood agar-plates, no detectable zone was observed even when the concentration of H2O2 was increased to 0.15 mM. With brain heart infusion-agar and chemically defined medium-agar plates, a profound zone was detected at 0.015 mM concentration of H2O2. To determine the minimal inhibitory concentration (MIC) of the strain in culture broth, various concentrations of H2O2 (0-200 mM) were maintained in the medium prior to fermentation. The result showed that for higher concentrations of H2O2 in the medium, the greater was the inhibition. Streptococcus is catalase-negative and known to produce H2O2 which may affect growth, HA production and glucose utilization. In order to determine at which growth phase H2O2 had the maximum inhibitory activity, a batch fermentation of S. zooepidemicus was conducted in shake flask culture. It was found that H2O2 production took place during the growth phase, and HA production started after the growth had reach late exponential phase when H2O2 in the culture media was depleted. This indicates that H2O2 produced by the cells did not affect cell growth but influenced HA production. [source] Enhanced Hyaluronic Acid Production in Bacillussubtilis by Coexpressing Bacterial HemoglobinBIOTECHNOLOGY PROGRESS, Issue 5 2007Liang-Jung Chien Bacillus subtilis strains that can produce hyaluronic acid (HA) were constructed by integrating the HA synthase gene (hasA) and the UDP-glucose dehydrogenase gene of group C Streptococcus (hasB) or of B. subtilis itself (tauD) into the amyE locus of the B. subtilis chromosome. All of the inserted genes were under the control of a strong constitutive vegII promoter of B. subtilis. Although HA production could be achieved by expressing hasA alone, coexpressing hasB or tauD with hasA could enhance HA production at least 2-fold. To replenish the energy consumed for HA biosynthesis, Vitreoscilla hemoglobin (VHb) was coexpressed with the HA-expressing genes. With the expression of VHb, not only the cell concentration was enhanced 25%, but also HA production was further increased by 100%. About 1.8 g/L of HA was obtained by the recombinant strain B.subtilis carrying VHb, hasA, and tauD genes in the expression cassette after 30 h cultivation. [source] Optimization of Rosmarinic Acid Production by Lavandula vera MM Plant Cell Suspension in a Laboratory BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2005Atanas I. Pavlov The all-round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula veraMM cell suspension was studied in a 3-L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X1) concentration between 10% and 50%; agitation (X2) between 100 and 400 rpm; and temperature (X3) between 22 and 30 °C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. veraMM: dissolved oxygen (X1*), 50% of air saturation; agitation (X2*), 400 rpm; and temperature (X3*), 29.9 °C, where maximal yield (Ymax) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake-flasks cultivation). [source] Continuous Cultivation of the Diatom Nitzschia laevis for Eicosapentaenoic Acid Production: Physiological Study and Process OptimizationBIOTECHNOLOGY PROGRESS, Issue 1 2002Zhi-You Wen The continuous cultures of the diatom Nitzschia laevis were performed at different dilution rates ( D) and feed glucose concentrations ( S0) to investigate cellular physiological responses and its production potential of eicosapentaenoic acid (EPA). Steady-state cell dry weight, residual glucose concentration, cell growth yield, specific glucose consumption rate, and fatty acid profiles were investigated within the range of D from 0.1 to 1.0 day,1 ( S0 fixed at 20 g/L) and the range of S0 from 5 to 35 g/L ( D fixed at 0.3 day,1), respectively. The highest EPA productivity of 73 mg L -1 day -1 was obtained at D = 0.5 day,1 and S0 = 20 g/L. However, when the continuous culture achieved high productivities of EPA at certain dilution rates and feed glucose concentrations, glucose in the feed could not be consumed completely. Accordingly, the continuous culture was evaluated in terms of both EPA productivity ( P) and glucose assimilation efficiency ( E). The parameter ,, defined as the product of P and E, was used as an overall performance index. Since , is a function of the two independent variables Dand S0, we employed a central composite design to optimize D and S0 for the highest , value. Based on the experimental results of the design, a second-order polynomial equation was established to represent the relationship between , and D and S0. The optimal values of D and S0 were subsequently determined as 0.481 day,1 and 15.56 g/L, respectively by the empirical model. The verification experiment confirmed the validity of the model. Under the optimal conditions, , value reached 46.5 mg L -1 day -1, suggesting a considerably high efficiency of the continuous culture of N. laevis in terms of EPA production and glucose utilization. [source] The Molecular Mechanism of Tropospheric Nitrous Acid Production on Mineral Dust SurfacesCHEMPHYSCHEM, Issue 10 2008R. Joel Gustafsson Dr. Tropospheric model: The formation of tropospheric nitrous acid on mineral surfaces does not involve an N2O4 intermediate. Well-defined surface conditions achievable under ultra-high vacuum are utilised to show that the hydrolysis reaction involves dissociated water (see figure). [source] Design of a Tubular Loop Bioreactor for Scale-up and Scale-down of Fermentation ProcessesBIOTECHNOLOGY PROGRESS, Issue 5 2003Maria Papagianni Microorganisms traveling through circulation loops in large-scale bioreactors experience variations in their environment such as dissolved oxygen concentration and pH gradients. The same changes are not experienced in small bioreactors, and it is suggested that herein lies one of the major reasons for the problems encountered when translating fermentation data from one scale to another. One approach to study this problem is to look at the circulation loop itself. The present work concerns an attempt to simulate the circulation loops inside stirred tank reactors, using a tubular loop reactor specially constructed for the purpose. The reactor carries a number of ports and probes along its length for the determination of concentration gradients within. The broth is circulated around the loop by the use of peristaltic pumps, and the circulation time (tc, s) is used as a measure of simulated reactor size. The reactor system has been evaluated using the citric acid fermentation by Aspergillus niger as a test process. Acid production and fungal morphology, in terms of the mean convex perimeter of mycelial clumps quantified by image analysis, were used as the parameters of evaluation for the two systems in comparison. From comparative experiments carried out in 10 and 200 L stirred tank bioreactors, it appears that the loop reactor simulates the corresponding stirred tank representing a valuable tool in scaling up and scaling down of fermentation process. [source] The complex oral microflora of high-risk individuals and groups and its role in the caries processCOMMUNITY DENTISTRY AND ORAL EPIDEMIOLOGY, Issue 4 2005David Beighton Abstract , The involvement of the oral biofilm in the caries process requires re-evaluation. The essential role of mutans streptococci (Streptococcus mutans and Streptococcus sobrinus) in the caries process is not proven. Acid production by dental plaque is not dependent upon the presence of mutans streptococci; caries occurs in the absence of these species and their presence does not necessarily indicate caries activity. Other oral bacteria, non-mutans streptococci, Actinomyces spp. and Bifidobacterium spp., are acidogenic and aciduric. They outnumber mutans streptococci in dental plaque, and there are data which support a role for these bacteria in the initiation and progression of caries. Molecular studies demonstrate the great diversity and complexity of the flora associated with caries. Many taxa identified have not been cultured and the role of these taxa is not known. We have, in mutans streptococci, good markers of disease but not necessarily the aetiological agents of the disease. Considerably more research is required to investigate the transition of tooth surfaces from being intact and sound to the white spot lesion stage. A combination of conventional and molecular approaches are required to elucidate the involvement of an individual taxon and of microbial populations with particular traits in the caries process. [source] Diabetic embryopathy: Studies using a rat embryo culture system and an animal modelCONGENITAL ANOMALIES, Issue 3 2005Shoichi Akazawa ABSTRACT The mechanism of diabetic embryopathy was investigated using in vitro experiments in a rat embryo culture system and in streptozotocin-induced diabetic pregnant rats. The energy metabolism in embryos during early organogenesis was characterized by a high rate of glucose utilization and lactic acid production (anaerobic glycolysis). Embryos uninterruptedly underwent glycolysis. When embryos were cultured with hypoglycemic serum, such embryos showed malformations in association with a significant reduction in glycolysis. In a diabetic environment, hyperglycemia caused an increased glucose flux into embryonic cells without a down-regulation of GLUT1 and an increased metabolic overload on mitochondria, leading to an increased formation of reactive oxygen species (ROS). Activation of the hexamine pathway, subsequently occurring with increased protein carbonylation and increased lipid peroxidation, also contributed to the increased generation of ROS. Hyperglycemia also caused a myo-inositol deficiency with a competitive inhibition of ambient glucose, which might have been associated with a diminished phosphoinositide signal transduction. In the presence of low activity of the mitochondrial oxidative glucose metabolism, the ROS scavenging system in the embryo was not sufficiently developed. Diabetes further weakened the antioxidant system, especially, the enzyme for GSH synthesis, ,-GCS, thereby reducing the GSH concentration. GSH depletion also disturbed prostaglandin biosynthesis. An increased formation of ROS in a diminished GSH-dependent antioxidant system may, therefore, play an important role in the development of embryonic malformations in diabetes. [source] Effect of citric acid and 1,2-dihydroxybenzene 3,5-disulfonic acid on crystallization of calcium sulfate dihydrate under simulated conditions of phosphoric acid productionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2005M. M. Rashad Abstract The effect of citric acid and 1,2-dihydroxybenzene 3,5-disulfonic acid (DHBDSA), as additives, on the crystallization of gypsum was studied under simulated conditions of the of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 °C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation. Addition of citric acid increased the induction time and decreased the growth efficiency while addition of DHBDSA decreased the induction time and increased the growth efficiency compared with in absence of additives. The crystals mean and median diameters were found to decrease in the presence of citric acid and increased in the presence of DHBDSA. The surface energy decreased with citric acid and increased with DHBDSA compared to the baseline (without additives). Interestingly, the majority of the formed crystals are tabular with DHBDSA and needle-like type with citric acid and baseline [source] Glycolic Acid Treatment Increases Type I Collagen mRNA and Hyaluronic Acid Content of Human SkinDERMATOLOGIC SURGERY, Issue 5 2001Eric F. Bernstein MD Background. Chronic solar irradiation results in both morphologic and functional changes in affected skin. ,-hydroxy acids, such as glycolic acid, have been shown to improve photodamaged skin. Objective. To investigate alterations in collagen gene induction and epidermal and dermal hyaluronic acid production as a result of administered glycolic acid. Methods. In this study we compared collagen gene expression from skin biopsy specimens, and epidermal and dermal hyaluronic acid immunohistochemical staining between glycolic acid-treated and vehicle-treated skin. Forearm skin was treated with 20% glycolic acid lotion or a lotion vehicle control twice a day for 3 months. Results. Epidermal and dermal hyaluronic acid and collagen gene expression were all increased in glycolic acid-treated skin as compared to vehicle-treated controls. Conclusion. Our data suggest that epidermal and dermal remodeling of the extracellular matrix results from glycolic acid treatment. Longer treatment intervals may result in collagen deposition as suggested by the measured increase in mRNA. [source] MODIFIED ENDOSCOPIC CONGO RED TEST: A RAPID METHOD TO VISUALIZE GASTRIC ACID SECRETIONDIGESTIVE ENDOSCOPY, Issue 1 2003Ervin Tóth Background:, The conventional endoscopic Congo red test (CRT) permits visualization of acid-producing mucosa. However, the CRT has not been disseminated into clinical endoscopy, which is partly due to the substantial prolongation of the gastroscopic examination. Methods:, Five healthy volunteers and 551 patients were included in a study designed to develop a more rapid approach based on the CRT. In this modified endoscopic Congo red test (MCRT), 0.2 µg/kg of pentagastrin was given intravenously to stimulate gastric acid production. The technical feasibility, tolerability, reproducibility, and inter- and intra-observer reliability of the MCRT were evaluated. Results:, The MCRT was as effective as the CRT (i.e. 6 µg/kg of pentagastrin was administered intramuscularly) in visualizing the extent of acid-producing gastric mucosa. Moreover, the MCRT significantly reduced the duration of examination by 63% (almost 8 min), compared to the CRT. Conclusions:, This MCRT is a simple, inexpensive, well-tolerated and reproducible method with low inter- and intra-observer variability and is well suited for endoscopy units with high workloads. [source] Biosensor online control of citric acid production from glucose by Yarrowia lipolytica using semicontinuous fermentationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2010Lucie Moeller Abstract Our study aimed at the development of an effective method for citric acid production from glucose by use of the yeast Yarrowia lipolytica. The new method included an automated bioprocess control using a glucose biosensor. Several fermentation methodologies including batch, fed-batch, repeated batch and repeated fed-batch cultivation were tested. The best results were achieved during repeated fed-batch cultivation: Within 3 days of cycle duration, approximately 100,g/L citric acid were produced. The yields reached values between 0.51 and 0.65,g/g and the selectivity of the bioprocess for citric acid was as high as 94%. Due to the elongation of the production phase of the bioprocess with growth-decoupled citric acid production, and by operating the fermentation in cycles, an increase in citric acid production of 32% was achieved compared with simple batch fermentation. [source] Identification and characterization of a new gene from Variovorax paradoxus Iso1 encoding N -acyl- d -amino acid amidohydrolase responsible for d -amino acid productionFEBS JOURNAL, Issue 19 2002Pei-Hsun Lin An N -acyl- d -amino acid amidohydrolase (N -D-AAase) was identified in cell extracts of a strain, Iso1, isolated from an environment containing N -acetyl- d -methionine. The bacterium was classified as Variovorax paradoxus by phylogenetic analysis. The gene was cloned and sequenced. The gene consisted of a 1467-bp ORF encoding a polypeptide of 488 amino acids. The V. paradoxusN -D-AAase showed significant amino acid similarity to the N -acyl- d -amino acid amidohydrolases of the two eubacteria Alcaligenes xylosoxydans A-6 (44,56% identity), Alcaligenes facelis DA1 (54% identity) and the hyperthermophilic archaeon Pyrococcus abyssi (42% identity). After over-expression of the N -D-AAase protein in Escherichia coli, the enzyme was purified by multistep chromatography. The native molecular mass was 52.8 kDa, which agreed with the predicted molecular mass of 52 798 Da and the enzyme appeared to be a monomer protein by gel-filtration chromatography. A homogenous protein with a specific activity of 516 U·mg,1 was finally obtained. After peptide sequencing by LC/MS/MS, the results were in agreement with the deduced amino acid sequence of the N -D-AAase. The pI of the enzyme was 5.12 and it had an optimal pH and temperature of 7.5 and 50 °C, respectively. After 30 min heat treatment at 45 °C, between pH 6 and pH 8, 80% activity remained. The N -D-AAase had higher hydrolysing activity against N -acetyl- d -amino acid derivates containing d -methionine, d -leucine and d -alanine and against N -chloroacetyl- d -phenylalanine. Importantly, the enzyme does not act on the N -acetyl- l -amino acid derivatives. The enzyme was inhibited by chelating agents and certain metal ions, but was activated by 1 mm of Co2+ and Mg2+. Thus, the N -D-AAase from V. paradoxus can be considered a chiral specific and metal-dependent enzyme. [source] Ambient pH controls the expression of endopolygalacturonase genes in the necrotrophic fungus Sclerotinia sclerotiorumFEMS MICROBIOLOGY LETTERS, Issue 2 2003Pascale Cotton Abstract In the necrotrophic fungus Sclerotinia sclerotiorum, secretion of polygalacturonases (PGs) and decrease of the environmental pH via oxalic acid production are considered as the main pathogenicity determinants. In order to evaluate the relationship between these two aspects of the infection process, we analyzed the expression of the endoPG-encoding genes pg1,3. Transcription of pg1,3 was not carbon regulated but was strictly controlled by pH and highly favored in a narrow range of acidic pH. During plant infection, a pH gradient was established in relation to oxalic acid secretion. Transcripts of pg1,3 were localized to the zone of colonization of healthy tissues while transcripts of genes encoding other lytic enzymes were restricted to the more acidic zones of the infected tissues. Our results show that progressive acidification of the ambient medium by the fungus is a major strategy for the sequential expression of pathogenicity factors. [source] Production of d -(,)-3-hydroxyalkanoic acid by recombinant Escherichia coliFEMS MICROBIOLOGY LETTERS, Issue 1 2003Kai Zhao Abstract Pathways for extracellular production of chiral d -(,)-3-hydroxybutyric acid (3HB) and d -(,)-3-hydroxyalkanoic acid (mcl-3HA) were constructed by co-expression of genes of ,-ketothiolase (phbA), acetoacetyl-CoA reductase (phbB) and 3-hydroxyacyl-ACP CoA transacylase (phaG), respectively, in Escherichia coli strain DH5,. The effect of acrylic acid and glucose on production of both 3HB and mcl-3HA was investigated. It was found that the addition of acrylic acid significantly increased production of 3HB and mcl-3HA consisting of 3-hydroxyoctanoic acid and 3-hydroxydecanoic acid in a ratio of 1:3 from 199 mg l,1 to 661 mg l,1 and from 27 mg l,1 to 135 mg l,1, respectively, in shake flask studies when glucose was present in the medium at the very beginning of fermentation. The timing of glucose addition had no effect on 3HB production. In contrast, mcl-3HA production was affected by glucose addition, an mcl-3HA concentration of 193 mg l,1 was obtained when glucose was added to the culture at 12 h. A more than seven-fold increase was obtained when compared with that in medium containing glucose at the beginning of fermentation. However, a decrease in production of 3HB and mcl-3HA was found when glucose was added at 12 h to the culture containing acrylic acid. The repressive effect of acrylic acid on acetic acid production was also evaluated and discussed. [source] Single QTL mapping and nucleotide-level resolution of a physiologic trait in wine Saccharomyces cerevisiae strainsFEMS YEAST RESEARCH, Issue 6 2007Philippe Marullo Abstract Natural Saccharomyces cerevisiae yeast strains exhibit very large genotypic and phenotypic diversity. However, the link between phenotype variation and genetic determinism is still difficult to identify, especially in wild populations. Using genome hybridization on DNA microarrays, it is now possible to identify single-feature polymorphisms among divergent yeast strains. This tool offers the possibility of applying quantitative genetics to wild yeast strains. In this instance, we studied the genetic basis for variations in acetic acid production using progeny derived from two strains from grape must isolates. The trait was quantified during alcoholic fermentation of the two strains and 108 segregants derived from their crossing. A genetic map of 2212 markers was generated using oligonucleotide microarrays, and a major quantitative trait locus (QTL) was mapped with high significance. Further investigations showed that this QTL was due to a nonsynonymous single-nucleotide polymorphism that targeted the catalytic core of asparaginase type I (ASP1) and abolished its activity. This QTL was only effective when asparagine was used as a major nitrogen source. Our results link nitrogen assimilation and CO2 production rate to acetic acid production, as well as, on a broader scale, illustrating the specific problem of quantitative genetics when working with nonlaboratory microorganisms. [source] Effect of lactic acid fermentation of onions (Allium cepa) on the composition of flavonol glucosidesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2007Barbara Bisakowski Summary Fermentation of red onions inoculated with Lactobacillus plantarum S1 (starter treatment) resulted in acid production to pH 4.5, after 48 h of incubation at 19 °C, which has proven to be adequate for proper preservation. In the presence of erythromycin (starter + antibiotic), acidification to pH 5.2 resulted, which was similar to that of the uninoculated control. The bacterial population was about 108 CFU mL,1 of brine after 3 days for the three treatments, suggesting that in the starter + antibiotic treatment, the antibiotic effectively suppressed the activity of the starter but not the native flora. Before lactic fermentation, the red onions contained 297.4 mg of total quercetin (Q) per kg wet weight, which consisted of 58.3%, 41.6% and 0.1% in quercetin diglucoside (Qdg), quercetin monoglucoside (Qmg) and free Q, respectively. For the starter treatment, Qdg decreased to 41.8% and 18.3% at 48 and 72 h, respectively, and a substantial amount of free Q had accumulated. The fermentation substantially increased the proportion of Qmg, which may have a positive effect as fractions containing higher ratios of Qmg to Qdg have been reported to have higher antioxidant activity. [source] Probiotic characteristics of lactic acid bacteria isolated from kimchiJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2010J.-H. Chang Abstract Aims:, The present work was aimed at identifying strains of lactic acid bacteria (LAB) from kimchi, with properties suitable for use as starter cultures in yogurt fermentation. Methods and Results:, A total of 2344 LAB strains were obtained from two different sources, one group consisted of commercial LAB strains from kimchi, and the second group consisted of those strains isolated from various types of kimchi. The LAB strains from both groups were screened for resistance to biological barriers (acid and bile salts), and the four most promising strains were selected. Further analysis revealed that KFRI342 of the four selected strains displayed the greatest ability to reduce the growth of the cancer cells, SNU-C4. The in vivo efficacy of strains in quinone reductase induction assay was evaluated, and the extent of DNA strand breakage in individual cells was investigated using the comet assay. Strain KFRI342 was identified as Lactobacillus acidophilus by 16S rRNA sequence analysis, showed protection against tumour initiation and imparted immunostimulation as well as protection against DNA damage. Conclusions:, Strain KFRI342, which showed probiotic characteristics reducing cancer cell growth, could be a suitable starter culture for yogurt fermentation because of its strong acid production and high acid tolerance. Significance and Impact of the Study:, This is the first report to describe a bacterium, isolated from kimchi, Lact. acidophilus KFRI342 which has the probiotic characteristics and the acid tolerance needed for its use as a starter culture in yogurt fermentation. [source] A novel finding that Streptomyces clavuligerus can produce the antibiotic clavulanic acid using olive oil as a sole carbon sourceJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008G. Efthimiou Abstract Aims:, This study aims to establish whether commercially available food oils can be used by Streptomyces clavuligerus as sole carbon sources for growth and clavulanic acid production. Methods and results:, Batch cultures in bioreactors showed that Strep. clavuligerus growth and clavulanic acid yields in a P-limited medium containing 0.6% (v/v) olive oil were respectively 2.5- and 2.6-fold higher than in a glycerol-containing medium used as control. Glycerol- and olive oil-grown cells present different macromolecular composition, particularly lipid and protein content. Conclusions:,Streptomyces clavuligerus uses olive oil as the sole carbon and energy source for growth and clavulanic acid production. Yields and production rates in olive oil are comparable to those reported for oil-containing complex media. Differences in yields and in the macromolecular composition indicate that different metabolic pathways convert substrate into product. Significance and impact of the study:, This is the first report of oils being used as the sole carbon source by Strep. clavuligerus. Apart from economic benefits, interesting questions are raised about Strep. clavuligerus physiology. Defined culture media allow physiological studies to be performed in the absence of interference by other compounds. Understanding how Strep. clavuligerus catabolises oils may have an economic impact in clavulanic acid production. [source] Evaluation of the fermentability of oat fractions obtained by debranning using lactic acid bacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2008G. Kedia Abstract Aims:, The overall kinetics of the fermentation of four oat fractions obtained by debranning using three potentially probiotic lactic acid bacteria were investigated. The main objective was to study the suitability of these fractions as fermentation media for the growth and the metabolic production of bacteria isolated from human intestine. Methods and Results:, The cell growth, lactic acid production and substrate uptakes of the three lactobacilli was monitored for 30 h. An unstructured mathematical model was used to describe and fit the experimental data. In the medium from fraction B (1,3% pearlings or ,-glucan-rich fraction) all strains reached the highest cell populations, maximum growth rates and maximum lactic acid productions. This could be because of the high levels of total fibre and ,-glucan of this fraction. Limited growth and lactic acid formation was found in medium A (0,1% pearlings or bran-rich fraction). Conclusions:, Medium B (1,3% pearling fraction) is the most suitable for fermentation and produces considerably higher probiotic cell concentrations. Significance and Impact of the Study:, Debranning technology could be used to separate fractions from cereal grains for the production of functional formulations with higher probiotic levels than the ones that were obtained with the whole grain. [source] A cost effective fermentative production of succinic acid from cane molasses and corn steep liquor by Escherichia coliJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2006L. Agarwal Abstract Aim:, Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. Methods and Results:, Initially, 0·8 gl,1 of succinic acid was produced in 60 h in 300-ml medium. On optimization, glucose and peptone were replaced by cane molasses and corn steep liquor. Three hundred ml of this medium was inoculated with 4% (v/v) of seed inoculum, incubated at 39°C for 72 h, resulted in 7·1 gl,1 of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO2 supply in this medium resulted in 17 gl,1 of succinic acid in 30 h. Conclusions:, A ninefold increase in succinic acid production was obtained in 500-ml anaerobic bottles with optimized medium having cane molasses and corn steep liquor as against initial medium containing glucose and peptone. However, a subsequent scale up in a 10-l fermentor resulted in a 2·5-fold increase in succinic acid production as against optimized medium used in 500-ml anaerobic bottles. Significance and Impact of the Study:, Succinic acid production was enhanced in medium consisting of inexpensive carbon and nitrogen sources in a shorter span of time. [source] Effect of culture conditions on lactic acid production of Tetragenococcus speciesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2004T. Kobayashi Abstract Aims:, To investigate the effects of the salt concentration, incubation temperature and initial pH of the medium on the fermentative ability of the halophilic lactic acid bacteria, Tetragenococcus muriaticus and T. halophilus. Method and Results:, The growth, lactic acid production and pH reduction ability of five strains of T. muriaticus and T. halophilus in MRS broth medium under various culture conditions such as salt concentration (3, 7, 15 and 23% NaCl), temperature (20, 30 and 40°C), and initial medium pH (5·8, 6·5 and 7·5) were investigated. Those of T. halophilus were seriously affected by a high salinity (23% NaCl); in contrast, those of T. muriaticus were affected by a low initial pH (5·8). Conclusions:, The results indicate that high saline concentrations and low pH values have significant impact on the growth, lactic acid production and pH reduction ability of T. halophilus and T. muriaticus, respectively. Significance and Impact of the Study:, This study appears to be important in biopreservation during the manufacture of fermented food products. Both T. muriaticus and T. halophilus may support each other in reducing pH in hypersaline or low pH environment. To our knowledge, this is the first report on the fermentation ability of T. muriaticus. [source] An in vitro study of the pH-lowering potential of salivary lactobacilli associated with dental cariesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2001M.C. Badet M.C. BADET, B. RICHARD AND G. DORIGNAC. 2001. Aims: Lactobacilli are known to produce acids from sucrose or glucose. This acid production can cause a drop in pH which is sufficiently significant to demineralize the hard tissues of the teeth. Some authors have demonstrated the benefits of substituting sorbitol or xylitol for sucrose. The aim of this work was to study the acid production of salivary lactobacilli with one test sugar (glucose) and two polyols (sorbitol and xylitol). Methods and Results: The pH-lowering potential of three strains of oral lactobacilli was recorded with glucose or one of the polyols at three different concentrations. The results showed that polyols were broken down by certain strains of lactobacilli. When this degradation took place, the pH dropped to values sufficiently low to demineralize the hard tissues of the teeth. Conclusions: Further studies must be carried out on the metabolism of polyols before encouraging their widespread substitution for sucrose. [source] Biochemical properties of Streptococcus macedonicus strains isolated from Greek Kasseri cheeseJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000M.D. Georgalaki A total of 32 Streptococcus macedonicus strains, isolated from Greek Kasseri cheese, were screened for biochemical properties of technological importance in milk fermentation processing, such as acid production, proteolytic and lipolytic activity, citrate metabolism, exopolysaccharide production, antimicrobial activity and biogenic amines production. All strains were found to be moderate acidifiers in milk. Only four strains could hydrolyse milk casein, while 11 strains showed lipolytic activity against tributyrin. Using amino acid derivatives of 4-nitroaniline as substrates, the highest peptidase activities were determined against phenylalanine- and glycine-proline-4-nitroanilide. Using fatty acid derivatives of 4-nitrophenol, it was shown that all strains exhibited esterase activities up to caprylate, with highest values against butyrate and caproate. Only one showed activity up to palmitate; this was also the most active strain against tributyrin. Five of the 32 strains could metabolize citrate but none of them produced exopolysaccharides. Nine strains displayed antimicrobial activity towards Clostridium tyrobutyricum, while no antimicrobial activity was detected against Listeria innocua and Propionibacterium freudenreichii subsp. shermanii. Finally, none was able to decarboxylize ornithine, histidine or lysine, and only four strains produced tyramine from tyrosine. [source] | ||||||||||||||||||||||||||||||||||