Lactic acid inhibitors

The products by cell growth, such as ethyl alcohol and lactic acid, occasionally inhibit cell growth. In such cases, the product is considered to inhibit cell growth in the same way as inhibitors do in enzyme reactions, and the following equation (which is similar to Equation 3.41, for noncompetitive inhibition in enzyme reactions) can be applied ... 

Fumaric Aero Inhibition. Another means of preventing malo-lactic fermentation is to add fumaric acid after alcoholic fermentation is complete (45, 46, 47,48). The inhibition is relative and its extent is dependent on the amount added. The susceptibility to fumaric acid is also dependent on the strain of malo-lactic bacteria tested (49). However, we know of no case where fumaric acid addition at the levels suggested by Cofran and Meyer (45) (about 0.05%) did not delay malo-lactic fermentation under normal winemaking conditions. This includes several experiments from our pilot winery (50). Nevertheless, we have not been hasty to recommend the use of fumaric acid as an inhibitor because 1) of the difficulty in solubilizing the acid in wine 2) we do not know the mechanism of action of its inhibition [Pilone (47, 48) has shown that the bacteria metabolize low levels of fumaric acid to lactic acid but, at inhibitory levels at wine pH, the acid is bactericidal] and 3) of the desirability of minimizing the use of chemical additives. 

Peptide mimetics containing the a-ketoamide moiety are very important because they act as cysteine protease inhibitors. In fact, the a-ketoamide residue forms hemithioacetals with the -SH group of the cysteine residue of the enzyme [32], Nakamura et al. [26b] reported the preparation of a 100-member combinatorial library of a-ketoamides by means of a two-step one-pot synthesis. The first step consisted of the Ugi-4CR between (+/— )lactic acid, amines, isocyanides, and aldehydes leading to the formation of the lactamides 40 which were oxidized to the corresponding pyruvamides 41. This one-pot procedure was performed in THF since the PDC oxidation was incompatible with the presence of methanol. Five a-ketoamides showed an 80% average purity (Scheme 2.17). 

Abbreviations CEL, cellulose DXM, dexamethasone EIPA, ethylisopropylamiloride FIB, fibrin MR methylprednisolone NA, not available Neo-R, neointima reduction PC, phosphorylcholine PCL, polycaprolactone PFM-P75, polyfluoroalkoxyphosphazene PLLA(PLA), poly-L-lactic acid POP, polyorganophosphazene PU, polyurethane Q-DL, Quanam drug eluting stent Q-M, Quanam metal stent SNR sodium nitroprusside TIMP, tissue inhibitors of metalloproteinase. 

Of the two major weak organic acids produced by LAB (acetic and lactic acid), acetic acid is the strongest inhibitor because of its higher dissociation constant (pKa = 4.75) as compared to lactic acid (pKa = 3.08) at a given molar concentration and pH level (Eklund, 1983 Holzapfel et al., 1995 Ouwehand, 1998). 

Yurdugul, S. and Bozoglu, F. 2002. Studies on an inhibitor produced by lactic acid bacteria of wines on the control of malolactic fermentation. Eur. Food Res. Technol. 215, 38-41. 

Findings from a study done on acid-adapted Salmonella to lactic acid rinses from artificially inoculated beef muscle slices showed that acid-adapted strains were not any more resistant to acid decontamination than parental strains (Dickson and Kunduru, 1995). In a study done by Steiner and Sauer (2003), the overexpression of the ATP-dependent heli-case RecG was found to increase resistance to weak organic acids in E. coli. This was achieved by reduction of the toxic effects of the organic acids, reduction of the effects of the synthetic uncouplers (CCCP and DNP), and a reduction of the ATPase and cytochrome c inhibitor azide as a result of a decrease in pH or available ATP. In LAB, resistance mechanisms to... 

Potassium sorbate is used as a yeast inhibitor for the stabilization of table wines containing residual sugar. When conditions permit the growth of lactic acid bacteria, wines treated with sorbic acid can develop an odor resembling crushed geranium leaves (Burkhardt, 1973 Radler, 1976 Wurdig et al., 1975). This result due to bacterial reduction... 

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