Organic acid microbial production

The degradation of carbohydrates leads, directly or indirectly, to various products, including carbon dioxide, organic acids, microbial polysaccharides, and humic substances. It has often been maintained that carbohydrates are transformed into the dark-colored humic substances by chemical and microbial processes. ... 

Lactic acid [50-21-5] (2-hydroxypropanoic acid), CH CHOHCOOH, is the most widely occurring hydroxycarboxylic acid and thus is the principal topic of this article. It was first discovered ia 1780 by the Swedish chemist Scheele. Lactic acid is a naturally occurring organic acid that can be produced by fermentation or chemical synthesis. It is present ia many foods both naturally or as a product of in situ microbial fermentation, as ia sauerkraut, yogurt, buttermilk, sourdough breads, and many other fermented foods. Lactic acid is also a principal metaboHc iatermediate ia most living organisms, from anaerobic prokaryotes to humans. 

Many of the by-products of microbial metaboHsm, including organic acids and hydrogen sulfide, are corrosive. These materials can concentrate in the biofilm, causing accelerated metal attack. Corrosion tends to be self-limiting due to the buildup of corrosion reaction products. However, microbes can absorb some of these materials in their metaboHsm, thereby removing them from the anodic or cathodic site. The removal of reaction products, termed depolari tion stimulates further corrosion. Figure 10 shows a typical result of microbial corrosion. The surface exhibits scattered areas of localized corrosion, unrelated to flow pattern. The corrosion appears to spread in a somewhat circular pattern from the site of initial colonization. 

Immobilisation of Microbial Cells for the Production of Organic Acid and Ethanol... 

Sauer, M., Porro, D., Mattanovich, D. and Branduardi, P. (2008) Microbial production of organic acids expanding the markets. Trends in Biotechnology, 26 (2), 100-108. 

Diacids. The microbial generation of mahc, fumaric, and succinic acid essentially imphes Krebs cycle pathway engineering of biocatalytic organisms to overproduce oxaloacetate as the primary four-carbon diacid that subsequently undergoes reduction and dehydration processes (Scheme 2.9). The use of these four-carbon diacids as intermediate chemicals and the state of their desirable microbial production is briefly outlined. 

A process of bacterial degradation of carbon compounds can be conceived essentially as a conversion from a C02-predominant to a CH4-predominant system (Stumm and Morgan, 1981). The production of organic methane by microbial activity is a typical example of such conversion. Organic matter is first transformed into organic acids, which are then decomposed into acetic acid, gaseous hydrogen, and CO2, and finally recombined as CH4 ... 

The versatility of microbial natural products is enormous. The most industrially important primary metabolites are the amino acids, nucleotides, vitamins, solvents, and organic acids. Millions of tons of amino acids are produced each year with a total mulfibillion dollar market. 

There are numerous reports describing the allelopathic (phytotmicrobial products on crop growth, particularly in conjunction with heavy residues from the previous crop (1-5). The cause of the reduced crop growth has been attributed to the production of a variety of toxic compounds such as phenolic acids, short-chain fatty acids, patulin, and many others (6-9). These compounds may be produced directly or indirectly during the microbial decomposition of organic residues under varying environmental conditions, such as when the soil remains wet over an extended period of time. 

By-products of anaerobic microbial metabolism include H2S, H2, CH4 and low molecular weight organic acids. Also the formation of FeS and the accumulation of microbial cell decomposition products can complicate the contamination problem. 

During the course of studies on the microbial production of chiral intermediates for D-pantothenic acid [2,134,135], Shimizu and co-workers found that several micro-organisms, such as Fusarium, Brevibacterium and so on, produce a novel enzyme that catalyzes the hydrolysis of aldonate lactones or aromatic lactones [136, 137],... 

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