Article info.

ABSTRACT

Received 21 Jan 2016
Revised 14 Aug 2016

Accepted 29 Jul 2017

The process of preliminary isolation and selection of lactic acid bacteria from Vietnamese traditional fermented vegetables is done based on (i) isolation and (ii) qualitative and quantitative analysis of lactic acid as the basis for the inspection and selection of lactic acid bacteria with strong antibacterial characteristics. The selected lactic acid bacteria were applied for yogurt fermentation with different bacterial densities (10⁴-10⁸ CFU/mL). The changes in pH value during fermentation time and sensory quality of product were evaluated. The research results showed that 48 strains were isolated from Vietnamese traditional fermented vegetables. Among them, 35 isolates (33 rod-shaped and 2 spherical-shaped) met the criteria of lactic acid bacteria. There were 15 isolates that were able to produce the highest amount of lactic acid, in which the rod-shaped bacteria showed better lactic acid producing capacity compared to the spherical-shaped ones. Four strains (S1.2, S5.5, S5.7, XK1.4) of these 15 strains that were tested for antimicrobial activity based on the agar spot test and agar well diffusion test, could produce bacteriocin against Bacillus subtilis. Based on the result of DNA sequencing, strains XK1.4 and S1.2 with strong antibacterial activity belonged to Lactobacillus plantarum (similarities 97% and 99%). The yogurt that was prepared by inoculating 10⁸CFU/mL of starter cultures (strains XK1.4 and S1.2) had the pH value of 4.5 after incubating for 7 hours, and achieved the good sensory quality.

Keywords

Bacteriocin, isolation, lactic acid bacteria, pickled vegetables, qualitative, quantitative

Cited as: Thuy, N.M., Cuong, N.X., Thanh, N.V., Tuyen, N.T.M., 2017. Characterization of lactic acid bacteria isolated from pickled vegetables as potential starters for yogurt preparation. Can Tho University Journal of Science. Vol 6: 111-120.