Isolation and selection of Lactobacillus strains for fermentation of mung bean yoghurt

Abstract

This study aims to isolate and screen Lactobacillus strains from fermented products for application in the production of mung bean yoghurt. The results from 10 isolation sources yielded 19 lactic acid bacterial colonies on De Man, Rogosa and Sharpe (MRS) medium, of which seven strains were pre-selected based on criteria such as gram positive, catalase-negative, ability to degrade CaCO_₃, non-motile, rod- or coccus-shaped cell morphology, and strong lactic acid production (15.60-17.67 g/l). After evaluating their probiotic activity, two strains, DC1 and KC2, were selected due to their ability to produce protease and amylase enzymes and inhibit pathogenic bacteria. The optimal growth conditions for these strains were MRS medium with a pH of 6.5, a temperature of 37°C, an incubation time of 24 hours, and a shaking speed of 200 rpm. Additionally, strain KC2 utilised sucrose as an alternative carbon source, whereas DC1 maintained the original carbon and nitrogen sources. Preliminary testing results indicated that strain KC2 has great potential for fermenting mung bean yoghurt, making it a promising candidate for practical production.