Enhanced expression of lactate dehydrogenase genes in Lactobacillus using capsaicin enzyme

Abstract

Lactic acid is the most important organic acid produced by Lactic acid bacteria from sour milk. Lactic acid has wide application in pharmaceutical, chemical and food industries and also in the preparation of biodegradable polymers for medical uses such as surgical sutures, prostheses and controlled drug delivery systems. Lactic acid exists in two optically active stereo-isomers, the L(+) and the D(-). The L (+) lactic acid form is being preferred since the D(-) form is harmful in humans. Lactic acid can be manufactured either by chemical synthesis or by microbial fermentations. But microbial fermentation has significant advantage over the chemical system in utilizing cheap raw materials as substrates in L(+) lactate production. During microbial fermentation, to increase industrial productivity of lactic acid, genetic modification of starter culture is usually practised. However, Capsaicin (8- methyl-N-vanillyl-6-nonemide), an active ingredient of chili peppers(Capsicum annum), is said to increase the metabolic activity of Lactobacillus by triggering lactate dehydrogenase (LDH) gene responsible for conversion of pyruvate to lactate. Therefore the effect of capsaicin enzyme in enhancing ldh gene expression in Lactobacillus by continuous fermentation was studied thereby achieving economic feasibility.