Microorganisms acids

Cooling (4 C) Inhibition of bacteria, retention of volatile material Samples containing microorganisms, acidity, alkalinity, BOD, organic, C, P, and N, colour, odour... 

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. 

The product quaUty considerations for nonphotosynthetic microorganisms are similar to those for algae. Tables 6 and 7 present composition and amino acid analyses, respectively, for selected bacteria, yeasts, molds, and higher fungi produced on a large pilot-plant or commercial scale. Table 8 summarizes results of proteia quaUty and digestibiUty studies. 

Table 7. Amino Acid Content of Nonphotosynthetic Microorganisms Grown on Various Substrates, g/16 g N ...

In addition to its presence in fmits, S(—)-malic acid has been found in cultures of a variety of microorganisms including the aspergiUi, yeasts, species of Sekrotinia, and Penicillium brevicompactum. Yields of levorotatory malic acid as high as 74% of theoretical have been reported. Iron, manganese, chromium, or aluminum ions reportedly enhance malic acid production. S(—)-Mahc acid is involved in two respiratory metaboHc cycles the Krebs tricarboxylic acid... 

Biosynthesis ofS(— )-M llc Acid. Aqueous fumaric acid is converted to levorotatory malic acid by the intracellular enzyme, fumarase, which is produced by various microorganisms. A Japanese process for continuous commercial production of S(—)-mahc acid from fumaric acid is based on the use of immobilized Brevibacteriumflavum cells in carrageenan (32). The yield of pyrogen-free S(—)-mahc acid that is suitable for pharmaceutical use is ca 70% of the theoretical. 

Preparation. The industrial production of malonic acid is much less important than that of the malonates. Malonic acid is usually produced by acid saponification of malonates (9). Further methods which have been recendy investigated are the ozonolysis of cyclopentadiene [542-92-7] (10), the air oxidation of 1,3-propanediol [504-63-2] (11), or the use of microorganisms for converting nitriles into acids (12). 

The use of these sHmicides may result in an appreciable increase in the cost of producing paper. However, thein use often reduces downtime that is caused by slime and, therefore, increases production which more than compensates for the initial cost of the sHmicides. White water systems also often contain proteolytic microorganisms which attack the machine felts and reduce thein useful life. Control of this problem may be accompHshed by treating the felts with a sHmicide foUowed by cleaning with a mild acid (see INDUSTRIALANTIMICROBIALAGENTS). 

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