Microorganisms lactic acid bacteria

Like most microorganisms, lactic acid bacteria are sensitive to ethanol. Generally, in laboratory conditions, bacteria isolated from wine are inhibited at an alcoholic strength of around 8-10% volume. Results vary according to the genus, species, and strain. Ribereau-Gayon elal. (1975), found that cocci are altogether more sensitive to ethanol than are lactobacilli. At an alcohol content of 13% volume, more than 50% of the lactobacilli resist as opposed to only 14% of the cocci. 

Cells of microorganisms have constituted a portion of human food siace ancient times. Yeast-leavened baked products contain the residual nutrients from the yeast cells destroyed duriag bakiag (see Bakery processes and leavening agents). Cultured dairy products, such as yogurt, buttermilk, and sour cream, contain up to lO cells of lactic acid bacteria per gram (19) (see Milk and milkproducts). Other examples of fermented foods consumed siace early times iaclude fermented meats, fish, and soybean products. 

Bacteria occur normally in fresh fruit and vegetable tissues. A wide variety of microorganisms have been found on fresh fruits and vegetables, which include mesophilic bacteria, lactic acid bacteria, coliforms, and yeasts and molds (Nguyen-The and... 

Schillinger U and Holzapfel WH. 2006. Lactic acid bacteria. In De W. Blackburn C, editor. Food Spoilage Microorganisms. Cambridge Woodhead, pp. 541-578. 

Modern methods of livestock production are intensive and the environmental conditions stress the animals. The use of antibiotics promotes growth and protects the animals from otherwise certain infection under these conditions. Antibiotic-like compounds formed in lactic acid fermentations prevent proliferation of spoilage and pathogenic microorganisms and increase the shelf life of the products. Nisin is a antimicrobial produced by a lactic acid bacterium and is used in some countries as a food preservative. Some lactic acid bacteria are capable of favorably influencing the fecal flora in man and animals. 

In addition, the antibiotics and other bacteriocins were originally detected in lactic acid bacteria, but were later also found in other Gram-positive microorganisms [28]. Lactic acid bacteria are a group of non-spore-forming, anaerobic fermentative bacteria within the Gram-positives with low GC content. 

The proteolytic activation of bioactive sequences by lactic acid bacteria has been debated recently due to the great advantage of using food-grade microorganisms to enrich foods with bioactive substances (Gobbetti et al.,... 

Only a few types of microorganisms are able to survive and proliferate under the relatively high alcohol and low pH conditions which characterize most wines. Of these, yeast, acetic acid bacteria, and lactic acid bacteria are the most common. No pathogenic organisms are able to survive in wine. 

Enterobacter aerogenes, B. subtilis, P. fluorescens, and Serratia marces-cens produce acetoin by decarboxylation of a-acetolactate. However, yeasts and E. coli form acetoin from the acetaldehyde-TPP complex and free acetaldehyde (Rodopulo et al 1976). These organisms do not decarboxylate a-acetolactate, but use it to produce valine and pantothenic acid. In lactic acid bacteria, a-acetolactate is not used for valine or pantothenic acid synthesis, since these substances are required for growth (Law et al. 1976B Reiter and Oram 1962). In those microorganisms which can synthesize valine, this amino acid inhibits a-acetolactate synthesis (Rodopulo et al 1976). 

The correlation between chemical composition of microorganisms and their susceptibility to sakacin P, a bacteriocin produced by some lactic acid bacteria, was carried out by Oust et al. [53], It could be shown that at least some of the variations in the susceptibility to sakacin P in Listeria monocytogenes can be correlated to alterations in the chemical composition of the bacterial cell wall. 

A milk product is described having prophylactic activity due to cultured-milk strains of microorganisms. It includes several lactic acid bacteria (e.g., Lactobacillus acidophilus strain 317/402), and inulin from Jerusalem artichoke. 

Some microorganisms can specifically produce mannitol from glucose or fructose without making a sorbitol byproduct (Smiley et al., 1967 Song et al., 2002 Wisselink et al, 2002 Saha, 2003). Mannitol, at 180g/L, can be easily recovered from the fermentation broth by cooling crystallization. Thus, research efforts have been directed toward production of mannitol by fermentation and enzymatic means (Vandamme and Soetaert, 1995). In this paper, the authors review the production of mannitol by lactic acid bacteria. 

The survival rate of other microorganisms, such as lactic acid bacteria, has also been studied in the TIM. At the end of digestion, Marteau et al. [32] found a bacte-... 

Grbin et al. 2007). ATHP reduction may lead to EHTP. As ethanol is a precursor, mousy off-flavour occurs after alcoholic fermentation, preferably after lactic acid bacteria activity. It seems that the formation of mousiness may be induced by oxidation but it is not clear if the effect is on the microorganisms or in any chemical reaction stimulated by the redox potential. Other agents claimed to affect its production (high pH, low sulphite, residual sugar content) (Lay 2004 Snowdon et al. 2006 Romano et al. 2007) are also stimulators of microbial activity and so the true mechanisms are not yet clarified, but the non-enzymatic chemical synthesis has been ruled out in D. anomala (Grbin et al. 2007). 

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