Home About us Contact
|
Home About us Contact | ||
|
|
||
Mesophilic Bacteria (mesophilic + bacteria)
Selected AbstractsBiofilm Growth and Bed Fluidization in a Fluidized Bed Reactor Packed with Support Materials of Low Density,ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2004R.A. Saucedo-Terán Abstract Support materials of low-density for fluidized bed reactors provide several operational advantages, including lower energy requirements and proper biofilm growth balance. The aim of this investigation was to study the extent of biofilm growth and bed fluidization in an experimental reactor, using polyester resin (,pr,=,1220,kg/m3) and vitrified expanded perlite (,vep,=,1710,kg/m3) as alternative support materials to conventional silica sand. A noteworthy amount of biofilm was observed to be attached to both support materials from the very beginning of the bioreactor operation. Nevertheless, there were significant variations in biofilm growth and activity over the course of the experimental trials. For both perlite and polyester beds, the highest biofilm mass and the highest total number of mesophilic bacteria were observed between the 7th and the 10th day, showing a steady state trend at the end of the experimental runs. The chemical oxygen demand (COD) removal levels were concomitant with biofilm mass and total mesophilic bacteria changes, although the polyester bed efficiency was slightly higher than that for the perlite bed. As expected, the polyester bed was fluidized at a lower re-circulation flow compared to the perlite bed. Reactor back-washing was not required for these support materials since biomass excess was adequately separated by means of a special internal device. The efficiencies of removal of organic matter achieved were acceptable (up to 78,%) despite the low volume of the support material (25,%) and the low hydraulic retention time (30,min). [source] Technological characterization of the natural lactic acid bacteria of artisanal Turkish White Pickled cheeseINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2008ELIF DAGDEMIR The aim of this study was to characterize the lactic acid bacteria (LAB) isolated from White Pickled cheeses produced with traditional methods; and to improve the quality of cheesemaking with a selection of bacterial cultures from artisanal White cheeses. LAB were isolated and identified from 30 White Pickled cheese samples collected from various cities in Turkey. Also, the numbers of several microbial groups (total aerobic mesophilic bacteria, LAB, enterococci, coliforms, moulds and yeasts) of cheese samples were enumerated. Lactobacilli, lactococci and enterococci were the most abundant microbial groups. The numbers of Enterococcus and Lactobacillus isolates were higher than those of the other LAB. Enterococcus faecalis (24.43%), Enterococcus faecium (17.61%) and Lactobacillus fermentum (19.88%) isolates were the most frequently isolated species. Lactococcus strains showed the highest acidifying activity, followed by Enterococcus and Lactobacillus strains. Proteolytic activity of Enterococcus faecalis strains was higher than that of the other enterococci species, except Enterococcus avium strains. Within lactobacilli strains, the highest mean proteolytic activity was that of Lactobacillus bifermentans, Lactobacillus brevis and Lactobacillus casei strains. [source] The effects of starter culture on chemical composition, microbiological and sensory characteristics of Turkish Ka,ar Cheese during ripeningINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 4 2007DURMU Ka,ar cheese samples were produced from raw milk and starter culture-added pasteurized milk. Chemical, microbiological and organoleptic properties of ka,ar cheeses were analysed at certain times during the ripening periods (on the 1st, 7th, 15th, 30th, 60th, 90th days). Generally, chemical parameters were not affected by starter culture. The pH, ripening index, water-soluble nitrogen and non-protein nitrogen did not show significant differences between the cheese samples. The addition of starter affected the microbiological quality of the cheeses. Starter culture-added ka,ar cheeses contained low levels of total aerobic mesophilic bacteria, moulds and yeasts, and coliforms, and achieved higher organoleptic scores than those of cheeses made from raw milk. The starter cultures contributed to acidity and microbial quality of the cheese. [source] EFFECTIVENESS OF CHLORINE AND NISIN-EDTA TREATMENTS OF WHOLE MELONS AND FRESH-CUT PIECES FOR REDUCING NATIVE MICROFLORA AND EXTENDING SHELF-LIFE,JOURNAL OF FOOD SAFETY, Issue 4 2002DIKE O. UKUKU ABSTRACT Efficacy of nisin-EDTA treatments as a sanitizing treatment for reducing native microflora of whole melons and extending shelf-life of fresh-cut pieces was compared to chlorine treatments. Whole cantaloupe and honeydew melons were washed with water, nisin (10 ,g/mL)-EDTA (0.02 M), or 200 ppm chlorine for 5 min at , 20C before fresh-cut preparation and storage at 5C for 15 days with periodic microbiological sampling. In addition, some fresh-cut pieces were washed with 10 ,g/mL nisin-EDTA or 50 ppm chlorine for 1 min before storage. Changes in appearance, odor, overall acceptability and the shelf-life of the minimally processed fresh-cut melons were investigated. Preliminary studies indicated that water washes, EDTA (0.002 to 0.2 M) or nisin (5 to 10 ,g/mL) were not effective in reducing the microflora of whole melon when used individually. Nisin-EDTA and chlorine treatments were significantly (P < 0.05) more effective in reducing native microflora than water washes. Nisin-EDTA treatments were significantly (P < 0.05) more effective than chlorine in reducing populations of yeast and mold and Pseudomonas spp. on whole melon surfaces but were not as effective as chlorine treatments for reducing aerobic mesophilic bacteria, lactic acid bacteria and total gram-negative bacteria. Microbial contaminants on fresh-cut pieces washed with 50 ppm chlorine or nisin-EDTA were further reduced. However, microbial populations increased throughout refrigerated storage irrespective of treatments. Odor, appearance, and overall acceptability ratings for cantaloupe and honeydew fresh-cut pieces treated with nisin-EDTA or chlorine were not significantly (P > 0.05) different from each other throughout the storage period (15 to 21 days). However, both treatments led to significantly (P < 0.05) improved ratings compared to the controls for the fresh-cut pieces at 9 to 12 days of storage and thereafter. The results of this study suggest that treatments with nisin-EDTA before and after fresh-cut processing would improve the quality and extend the shelf-life of fresh-cut melon. [source] Effect of Gamma-irradiation on Color, Pungency, and Volatiles of Korean Red Pepper PowderJOURNAL OF FOOD SCIENCE, Issue 8 2004J.H. Lee ABSTRACT: Effect of gamma-irradiation on color, pungency, and volatiles of Korean red pepper powder (Capsicum annuum L.) was investigated. Red pepper powder, vacuum-packaged in a polyethylene/polypropylene bag, was gamma-irradiated up to 7 kGy. An irradiation dose of 7 kGy reduced the population of mesophilic bacteria and fungi effectively without affecting major quality factors. Pungency of irradiated red pepper powder was not changed based on the amount of capsanoids by high-performance liquid chromatography (HPLC) and the Scoville sensory score. The red color of irradiated pepper powder was not significantly different from that of the control, judged from the capsanthin content by HPLC and color assessment using spectrophotpmetric (American Spice Trade Assn. units) and colorimetric measurements (Hunter a values). Further, the sensory evaluation showed no significant difference in pungent odor and off-odor between nonirradiated control and irradiated red pepper powder. However, when headspace volatiles of gamma-irradiated red pepper powder were evaluated by gas chromatography/ mass spectrometry with solid-phase microextraction and electronic nose with metal oxide sensors, the profiles of odor were classified into irradiated dose levels of 0, 3, 5, and 7 kGy by principal component analysis and multivariate analysis of variance. Such a difference of odor might result from the disappearance of some volatiles, such as hexanoic acid and tetramethyl-pyrazine, and the appearance of 1,3-di-tert-butylbenzene during irradiation. Moreover, it appears that the irradiation of packaging material induced a formation of 1,3-di-tertbutylbenzene, which migrated into the red pepper powder. [source] The ripening and aging of noni fruits (Morinda citrifolia L.): microbiological flora and antioxidant compoundsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2007Yanine Chan-Blanco Abstract The juice of noni fruit (Morinda citrifolia L.) is claimed to be a natural functional beverage with a growing market both in the USA and Europe. It is traditionally produced by keeping harvested fruit in closed containers for several weeks as the fruit senesces or ages. Little is known about the changes that occur in the juice's microbiological, physicochemical, and functional characteristics during this treatment. Traditional processing was simulated in the laboratory, with samples being recovered and analyzed at various time intervals. At first, fermentation occurred and populations of molds, yeasts, and mesophilic bacteria increased significantly. After 2 weeks, microbial growth changed abruptly, stopping for yeasts, molds, and mesophilic bacteria, and decreasing suddenly for lactic bacteria. Analyses of pH, soluble solids, ethanol, and lactic acid in the fruits confirmed the microbial analyses, indicating initial sensitive variations, followed by values remaining comparatively steady during aging. Vitamin C and total phenol contents also remained constant at 300 ± 60 mg and 50 ± 20 mg GAE, respectively, per 100 g of pulp. Antioxidant capacity likewise remained relatively high at 8 ± 1.5 µmol Trolox® g,1. All phenolic compounds, including scopoletin and rutin, varied significantly immediately after harvest but remained more or less steady during aging. Copyright © 2007 Society of Chemical Industry [source] An integrated analysis of the genome of the hyperthermophilic archaeon Pyrococcus abyssiMOLECULAR MICROBIOLOGY, Issue 6 2003Georges N. Cohen Summary The hyperthermophilic euryarchaeon Pyrococcus abyssi and the related species Pyrococcus furiosus and Pyrococcus horikoshii, whose genomes have been completely sequenced, are presently used as model organisms in different laboratories to study archaeal DNA replication and gene expression and to develop genetic tools for hyperthermophiles. We have performed an extensive re-annotation of the genome of P. abyssi to obtain an integrated view of its phylogeny, molecular biology and physiology. Many new functions are predicted for both informational and operational proteins. Moreover, several candidate genes have been identified that might encode missing links in key metabolic pathways, some of which have unique biochemical features. The great majority of Pyrococcus proteins are typical archaeal proteins and their phylogenetic pattern agrees with its position near the root of the archaeal tree. However, proteins probably from bacterial origin, including some from mesophilic bacteria, are also present in the P. abyssi genome. [source] | |||||||||||||