Proteolytic profile of lactic acid bacteria

Abstract

In the present study, twenty six strains of previously isolated lactic acid bacteria (LAB) were screened for protease production and the isolate showing highest enzyme activity, Lactococcus lactis subsp. lactis, was evaluated further. The highest protease activity in de Man Rogosa Sharpe (MRS) media was 1.1 Units/mL at pH 7.0 and incubation temperature of 37ºC with inoculum size of 5%, sucrose as carbon source, yeast extract as nitrogen source and casein as protein source without any agitation. When sourdough was supplemented with L. lactis, high protease activity was observed with Vigna mungo (20.26 Units/g) than plain dough (7 Units/g) at 37ºC and pH 7.0. Protease production remained unaltered by selected intrinsic and extrinsic factors (water activity, organophosphorus compounds and phytate content). Besides, it was found that water activity, phytate content and organophosphorus compounds (malathion) had negligible effect on protease activity of L. lactis. Visual and textural attributes indicated the overall general acceptability of dough containing Vigna mungo (8.15 ± 0.03) on a ten-point hedonic scale. Thus, the results suggetsed the potential of L. lactis as a proteolytic LAB strain.