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Microorganism Growth (microorganism + growth)

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Life Sciences50%

Selected Abstracts

Organic carbon and nitrogen removal in anoxic/oxic-membrane bioreactor treating high-strength wastewater

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009
Zhimin Fu
Abstract The performance of an anoxic/oxic membrane bioreactor system for the simultaneous removal of nitrogen and chemical oxygen demand (COD) was investigated. This process removed up to 87% of total nitrogen (TN) and 94% of COD, with the influent concentrations of 200 mg NH4+ -N/L and 4000 mg COD/L and a recycle ratio (R) of 200%. Biological assimilation and simultaneous nitrification and denitrification (SND) were considered on nitrogen removal process. The TN removal efficiency was above 87.5%, while the nitrogen being removed through SND was above 75.5% and nitrogen assimilated into the biomass was below 24.5%, with influent concentration below 200 mg NH4+ -N/L. Increasing the influent concentration to 400 mg NH4+ -N/L, TN removal efficiency decreased significantly to 37.5%, of which 49.5% was provided by microorganism growth. Batch experiments provided evidence for the phenomena of SND. Furthermore, the SND removal efficiency increased gradually from 26.8 to 90.0%. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source]

EFFECT OF DIFFERENT METHODS FOR APPLICATION OF AN ANTIFOG SHRINK FILM TO MAINTAIN CAULIFLOWER QUALITY DURING STORAGE

JOURNAL OF FOOD QUALITY, Issue 3 2003
J. R. DeELL
The antifog shrink film improved quality retention and cauliflower packaged using any of the four methods exhibited less weight loss than controls (unwrapped) after 23 days in storage at 0,1C or 10C. The overwrap and sealed bag treatments resulted in higher appearance ratings and less curd browning and butt discoloration after storage at 0,1C. Shrinking the film with heat and/or vacuum may have damaged the tissue, providing a more favorable environment for microorganism growth, since more decay was found on these curds. [source]

Kinetic Study of the Conversion of Different Substrates to Lactic Acid Using Lactobacillus bulgaricus

BIOTECHNOLOGY PROGRESS, Issue 3 2000
Concepción N. Burgos-Rubio
Lactic acid fermentation includes several reactions in association with the microorganism growth. A kinetic study was performed of the conversion of multiple substrates to lactic acid using Lactobacillusbulgaricus. Batch experiments were performed to study the effect of different substrates (lactose, glucose, and galactose) on the overall bioreaction rate. During the first hours of fermentation, glucose and galactose accumulated in the medium and the rate of hydrolysis of lactose to glucose and galactose was faster than the convesion of these substrates. Once the microorganism built the necessary enzymes for the substrate conversion to lactic acid, the conversion rate was higher for glucose than for galactose. The inoculum preparation was performed in such a way that healthy young cells were obtained. By using this inoculum, shorter fermentation times with very little lag phase were observed. The consumption patterns of the different substrates converted to lactic acid were studied to determine which substrate controls the overall reaction for lactic acid production. A mathematical model (unstructured Monod type) was developed to describe microorganism growth and lactic acid production. A good fit with a simple equation was obtained. It was found experimentally that the approximate ratio of cell to substrate was 1 to 10, the growth yield coefficient (YXS) was 0.10 g cell/g substrate, the product yield (YPS) was 0.90 g lactic acid/g substrate, and the , parameter in the Luedeking-Piret equation was 9. The Monod kinetic parameters were obtained. The saturation constant (KS) was 3.36 g/L, and the specific growth rate (,m ) was 1.14 l/h. [source]

Microbial interaction in cooked cured meat products under vacuum or modified atmosphere at 4°C

JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2002
J. Metaxopoulos
Aims: To investigate the antagonistic activity of two lactic acid strains against the spoilage microflora in cooked cured meat products, vacuum or modified atmosphere packed at 4°C and to determine the inhibitory capacity of their bacteriocins. Methods and Results: Frankfurter-type sausages and sliced cooked cured pork shoulder were inoculated with Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 or with their bacteriocins. The microbial, physico-chemical (pH, l - and d -lactate, acetate and ammonia) and colour changes were studied. Results under vacuum packaging showed that in the uninoculated samples of the pork product the spoilage microflora grew but in the inoculated ones the spoilage microorganisms (e.g. Brochothrix thermosphacta and enterococci) reduced during the storage. This observation was more pronounced in the samples with the addition of bacteriocins. In the frankfurter-type sausages the spoilage microflora did not grow in the uninoculated and inoculated samples. In the modified atmosphere enriched in CO2 the population of spoilage microflora remained at low levels in both products, indicating that CO2 has an effect on thespoilage microorganisms' growth. In the pork product the concentrations of acetate and d -lactate increased while l -lactate decreased, but in the frankfurter-type sausages increase of acetate and d -lactate was not observed. Conclusions: Lactic acid strains had an effect on the spoilage microflora growth but did not affect, negatively, the organoleptic properties of the products. These strains may be used as biopreservative cultures or their bacteriocins could be an important contribution to microbiological quality of meat products. Significance and Impact of Study: Establishment of biopreservation as a method for extension of shelf life of meat products. [source]