Characteristics and Antioxidant Activity of Lactiplantibacillus plantarum Fermented and Heat-treated Black Bean

Abstract

This study aimed to optimize the fermentation condition of black bean using probiotic lactic acid bacteria (LAB) and to evaluate characteristics and antioxidant activity of LAB fermented and heat-treated black bean. Two LAB strains were selected by analysis of acid resistance, bile resistance, antimicrobial activity, and antioxidant activity, and identified as Lactiplantibacillus plantarum CH9 and Lactiplantibacillus plantarum SU18 by 16S rRNA sequencing. Both strains showed similar or higher acid resistance, bile resistance and antimicrobial activity, compared to Lacticaseibacillus rhamnosus GG, a commercial probiotic strain. The heat-killed cells of CH9 and SU18 strains showed significantly (p<0.05) higher DPPH and ABTS radical scavenging activities than live cells. Fermentation of black bean (30%) treated with Alcalase using the two selected strains was found to be optimal condition, increasing viable cell count of LAB up to 10.8 Log CFU/g. During the fermentation, the titratable acidity of Alcalase-treated black bean was notably increased with concomitant decrease in the pH. LAB fermentation significantly (p<0.05) increased antioxidant activity based on DPPH and ABTS radical scavenging activities as well as total phenol content. In addition, total phenol content and antioxidant activity were significantly (p<0.05) enhanced by heat processing (121C, 15 min) of the fermented products. These findings are expected to be useful for the development of various LAB-fermented foods containing heat-killed probiotics.