Abstract
Jiaosu is a fermentation product using microorganisms to transform organic materials into bioactive ingredients, which plays an important role in food industry, healthcare, and environmental protection. In this study, 37 microbial strains, including 22 lactic acid bacteria (LABs) and six yeast, were isolated from six different Jiaosu, with three genera (Lactobacillus, yeast, and Bacillus) shared by the five Jiaosu. The strains had the highest frequency of catalase (59.5%), followed by protease (56.8%), β-glucosidase (54.1%), and lipase (40.5%), with lower frequency for cellulase (32.4%), pectinase (24.3%), and amylase (18.9%). Strains MZ3 and YT2 significantly inhibited pathogens Escherichia coli and Staphylococcus aureus, and strains MS2 and MZ3 inhibited Ralstonia solanacearum. DPPH free radical clearance was present in six strains including MZ1, MS4, and GJ2, while 25 strains showed over 60% clearance rate of ABTS, with the highest rate (96.2%) for strains GZ2, GS2, and MZ2. Nine strains were determined to have activities of SOD, POD, and CAT. All 37 strains had the ability to produce IAA, with higher IAA (25-135 μg/mL) for seven strains. Strains MS2, MS4, MJ6, and MJ4 were found to produce siderophores, and strains YH4, JS7, YJ2, and GH1 produced GABA. Fourteen LAB strains had acidic culture solution (pH < 4), and four of which were confirmed to produce organic acids, GABA, and IAA based on LC-MS. Therefore, functional strains were obtained from special Jiaosu, that is, organic acid-producing antagonist Weissella confusa MZ3, GABA, IAA-producing antagonist Pichia kudriavzevii YJ2 and rich hydrolase-synthesis Bacillus amyloliquefaciens GC1 and Lactobacillus plantarum YS2, which might be potential microbial agents to improve the fermentation of Jiaosu.