Abstract
BackgroundPhenyllactic acid (PLA), a novel antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi, can be produced by many microorganisms, especially lactic acid bacteria. However, the concentration and productivity of PLA have been low in previous studies. The enzymes responsible for conversion of phenylpyruvic acid (PPA) into PLA are equivocal.Methodology/Principal FindingsA novel thermophilic strain, Bacillus coagulans SDM, was isolated for production of PLA. When the solubility and dissolution rate of PPA were enhanced at a high temperature, whole cells of B. coagulans SDM could effectively convert PPA into PLA at a high concentration (37.3 g l−1) and high productivity (2.3 g l−1 h−1) under optimal conditions. Enzyme activity staining and kinetic studies identified NAD-dependent lactate dehydrogenases as the key enzymes that reduced PPA to PLA.Conclusions/SignificanceTaking advantage of the thermophilic character of B. coagulans SDM, a high yield and productivity of PLA were obtained. The enzymes involved in PLA production were identified and characterized, which makes possible the rational design and construction of microorganisms suitable for PLA production with metabolic engineering.
Highlights
Phenyllactic acid (PLA) has broad and effective antimicrobial activity against both bacteria and fungi and can be employed and developed as a new type of natural antiseptic agent to extend the shelf life of food and feed [1,2,3]
Isolation of thermophilic bacteria for PLA production Using the procedures described in Materials and Methods, 560 bacterial strains that grew at 50uC were tested for PLA production
Identification of the strain was confirmed by Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (DSMZ)
Summary
Phenyllactic acid (PLA) has broad and effective antimicrobial activity against both bacteria and fungi and can be employed and developed as a new type of natural antiseptic agent to extend the shelf life of food and feed [1,2,3]. It is a useful precursor for the synthesis of many important drugs, including Danshensu (3,4-dihydroxyphenyllactic acid) which can inhibit platelet aggregation and coronary artery disease, hypoglycemic reagents, protease inhibitors, and anti-HIV reagents [4,5,6,7,8]. The enzymes responsible for conversion of phenylpyruvic acid (PPA) into PLA are equivocal
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