Lactic acid producing organism

Fermentations in larger vessels and the final trade fermentation are conducted under quasi-stetile conditions, and yeast growth is accompanied by some growth of contaminant bacteria. These are generally lactic acid-producing organisms but are sometimes coHform bacteria the occurrence of Salmonella in fermentor Hquids has not been reported. Massive contamination with Oidium lactis or wild yeasts has been reported. 

Lactic acid producing organisms that do not have a phosphoketolase pathway can still produce acetate or ethanol, formed by the usual mixed acid fermentation, via pyruvate. This is the case for, for example, Lacto-coccus lactis [35]. 

Nutrients The most well-known lactic acid producing organisms, such as Lactobacillus and Lactococcus species, are members of the taxonomic order of Lactobacil-lales, also commonly referred to as lactic acid bacteria. These lactic acid bacteria have their really complex nutrient need in common [29]. Vitamins and peptides need to be added to the medium to enable growth. This can be done by adding peptones, yeast extract, or corn steep liquor, but this is expensive. Nutrients for lactic acid production can also be derived from nutrient-rich waste streams such as rice bran, fish waste, or vinification lees [46 8]. 

Food can be preserved by fermentation using selected strains nf yeast, lactic acid-producing bacteria, or molds. The production of ethanol, lactic and other organic acids, and anlimicrobial agents in the food, along with the removal of fermentable sugars, can yield a product having an extended shelf life. 

Rhizopus oryzae is an indispensable microorganism in industrial fermentation, as it is widely employed to produce L-lactic acid as well as other organic acids. This organism is able to produce only one stereospecific product (L-lactic acid), rather than a racemic mixture and can, therefore, fulfill the need for producing a food additive to be used as both acidulant and preservative. During L-lactic acid fermentation many other metabolites can be produced as by-products. These include fumaric acid, malic acid, ethanol, and the like. However, these metabolites can greatly influence the downstream process and the quality of the L(+)-lactic acid produced. Fumaric acid is the main by-product, as a result of a special metabolic pathway in L-lactic acid production by R. oryzae (Wang et al., 2005). 

Figure 10 shows the inherit advantage of lactic acid produced by the universal metabohc pathway shared by most living organisms from humans, to plants, to microbes. Through the anaerobic glycolysis pathway, two lactic acid molecules (A/ =90) are produced from one glucose (M =180) with a 100% theoretical yield (i.e., no loss at all). For the anaerobic fermentation of ethanol, the theoretical yield is around 51% with two CO M =AA) molecules lost per glucose. After ethanol has been dehydrated to ethylene and polymerized into bio-PE, the theoretical yield from glucose is only around 31% compared with 80% for PLA (Fig. 10). For PHBV-like biopolymer synthesized in microbial cells, the building block is typically acetyl-CoA with around 51% theoretical yield after the loss of CO (decarboxylation) from...

The heterofermentative strains normally have long rod-shaped cells but considerable variation in shape (pleomorphism) occurs, and short rods may develop. They grow best at SC C (86°F) and in the pH range 4-0-5-0. With an extended lag period, they can adapt to grow in a medium of lower pH, in the presence of hop resins and of ethanol. Beer may support growth when suitable nitrogenous compounds are present. The quantity of lactic acid produced usually reflects the concentration of carbohydrates in the beer available for assimilation by these organisms. 

The majority of the fomentation processes use species of Lactobacilli which give high yields of lactic acid. Some organisms predominantly produce the L isomo", such as Lactobacilli amylophilus, L. bavaricus, L. casei and... 

Currently, only few industrial products are produced from green biomass as carbon source, such as lactic acid and ammonium lactates (see chapter Microorganisms for Production of Lactic Acid and Organic Lactates), lysine (see chapter Microorgan isms for Biorefining of Green Biomass) or 2,3 butanediol. The use of green biomass... 

Microorganisms, which are able to produce lactic acid and organic lactates, are systematically classified and morphologically and biochemically characterized, and their different metabolic pathways for the formation of various lactic acid... 

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