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Culture Used (culture + used)
Selected AbstractsPROTECTIVE CULTURES USED FOR THE BIOPRESERVATION OF HORSE MEAT FERMENTED SAUSAGE: MICROBIAL AND PHYSICOCHEMICAL CHARACTERIZATIONJOURNAL OF FOOD SAFETY, Issue 3 2008JAZILA EL MALTI ABSTRACT In this paper, 150 isolates, originating from horse meat, were subjected to step-by-step screening and characterization to search for potential protective cultures to be used in the meat industry. Isolates were first tested on their homofermentative and salt tolerance. Second, the antibacterial capacities toward Listeria monocytogenes were determined in an agar spot test. In total, 50% of the tested isolates were inhibitory toward Listeria monocytogenes. However, only 12 isolates produced a bacteriocin. Finally, three isolates with the strong bacteriocin activity were evaluated on their competitive nature by comparing their growth rate, acidifying character and lactic acid production at 15C under anaerobic conditions in a liquid broth. All three isolates combined a fast growth rate with a deep and rapid acidification caused by the production of high levels of lactic acid. Lactobacillus sakei was used as starter culture for producing sausage horse meat. In this study, fermentations were followed analyzing the microbiological and physicochemical aspects of this product. The sausages were characterized by an important microbial activity of lactic acid bacteria that resulted in a product with a final pH of about 4.56. No Listeria monocytogenes, Salmonella spp. or sulfite reducing clostridia were ever isolated from the raw materials or the fermented sausages during the maturation, underlining the microbial safety of this product. The final water activity of the product was 0.85. Starter cultures showed that Lactobacillus sakei was really efficient in reducing the amine production since this strain caused a quick pH drop during sausage fermentation. PRACTICAL APPLICATIONS A starter culture can be defined as a microbial preparation of large numbers of cells of at least one microorganism to be added to a raw material to produce a fermented food by accelerating and steering its fermentation process. The group of lactic acid bacteria (LAB) occupies a central role in these processes, and has a long and safe history of application and consumption in the production of fermented foods and beverages. They cause rapid acidification of the raw material through the production of organic acids, mainly lactic acid. Also, their production of acetic acid, ethanol, aroma compounds, bacteriocins, exopolysaccharides and several enzymes is of importance. The main reason for suitability of LAB is their natural origin, and they can contribute to food safety and/or offer one or more organoleptic, technological, nutritional or health advantages. [source] Co-determination of ATP and proteins in Triton X 100 non-ionic detergent-opened monolayer cultured cellsLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Tamás K, szegi Abstract Human monolayer cells (HEp-2 and Hep G2) were cultured in 96-well plates. A modified Triton X 100 nonionic detergent extraction method was used for releasing intracellular ATP and protein in one step. The detergent technique was compared to perchloric acid (PCA) extraction. ATP was determined by the firefly bioluminescence method and ATP values were referred to cell protein (ATP:protein ratio). There was no significant difference in ATP data between detergent and PCA treatments. The ATP:protein ratio seems to be a sensitive tool for characterizing the metabolic activity of monolayer tissue culture cells. The protein-mobilizing capability of Triton X 100 depends on the type of cell culture used. Our modified extraction gives reliable ATP:protein values with one simple extraction step. Copyright © 2007 John Wiley & Sons, Ltd. [source] Microbiological and geochemical dynamics in simulated-heap leaching of a polymetallic sulfide oreBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2008Kathryn Wakeman Abstract The evolution of microbial populations involved in simulated-heap leaching of a polymetallic black schist sulfide ore (from the recently-commissioned Talvivaara mine, Finland) was monitored in aerated packed bed column reactors over a period of 40 weeks. The influence of ore particle size (2-6.5 mm and 6.5-12 mm) on changes in composition of the bioleaching microflora and mineral leaching dynamics in columns was investigated and compared to fine-grain (<2 µm) ore that was bioprocessed in shake flask cultures. Both column reactors and shake flasks were inoculated with 24 different species and strains of mineral-oxidizing and other acidophilic micro-organisms, and maintained at 37°C. Mineral oxidation was most rapid in shake flask cultures, with about 80% of both manganese and nickel and 68% of zinc being leached within 6 weeks, though relatively little of the copper present in the ore was solubilised. The microbial consortium that emerged from the original inoculum was relatively simple in shake flasks, and was dominated by the iron-oxidizing autotroph Leptospirillum ferriphilum, with smaller numbers of Acidimicrobium ferrooxidans, Acidithiobacillus caldus and Leptospirillum ferrooxidans. Both metal recovery and (for the most part) total numbers of prokaryotes were greater in the column reactor containing the medium-grain than that containing the coarse-grain ore. The bioleaching communities in the columns displayed temporal changes in composition and differed radically from those in shake flask cultures. While iron-oxidizing chemoautotrophic bacteria were always the most numerically dominant bacteria in the medium-grain column bioreactor, there were major shifts in the most abundant species present, with the type strain of Acidithiobacillus ferrooxidans dominating in the early phase of the experiment and other bacteria (At. ferrooxidans NO37 and L. ferriphilum) dominating from week 4 to week 40. With the coarse-grain column bioreactor, similar transitions in populations of iron-oxidizing chemoautotrophs were observed, though heterotrophic acidophiles were often the most abundant bacteria found in mineral leach liquors. Four bacteria not included in the mixed culture used to inoculate the columns were detected by biomolecular techniques and three of these (all Alicyclobacillus -like Firmicutes) were isolated as pure cultures. The fourth bacterium, identified from a clone library, was related to the Gram-positive sulfate reducer Desulfotomaculum salinum. All four were considered to have been present as endospores on the dried ore, which was not sterilized in the column bioreactors. Two of the Alicyclobacillus -like isolates were found, transiently, in large numbers in mineral leachates. The data support the hypothesis that temporal and spatial heterogeneity in mineral heaps create conditions that favour different mineral-oxidizing microflora, and that it is therefore important that sufficient microbial diversity is present in heaps to optimize metal extraction. Biotechnol. Bioeng. 2008;101: 739,750. © 2008 Wiley Periodicals, Inc. [source] Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese productsFEMS MICROBIOLOGY REVIEWS, Issue 3 2005Gerrit Smit Abstract Flavour development in dairy fermentations, most notably cheeses, results from a series of (bio)chemical processes in which the starter cultures provide the enzymes. Particularly the enzymatic degradation of proteins (caseins) leads to the formation of key-flavour components, which contribute to the sensory perception of dairy products. More specifically, caseins are degraded into peptides and amino acids and the latter are major precursors for volatile aroma compounds. In particular, the conversion of methionine, the aromatic and the branched-chain amino acids are crucial. A lot of research has focused on the degradation of caseins into peptides and free amino acids, and more recently, enzymes involved in the conversion of amino acids were identified. Most data are generated on Lactococcus lactis, which is the predominant organism in starter cultures used for cheese-making, but also Lactobacillus, Streptococcus, Propionibacterium and species used for surface ripening of cheeses are characterised in their flavour-forming capacity. In this paper, various enzymes and pathways involved in flavour formation will be highlighted and the impact of these findings for the development of industrial starter cultures will be discussed. [source] | |||||||||||||