MZ3

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  μ g/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.

The application of microbial fertilizer plays an important role in improving soil restoration and fertilizer utilization. The effects of microbial fertilizer are greatly affected by crop genotypes and ecological conditions. Little is known about the effects of microbial fertilizers on maize production in Northeast China. To develop microbial fertilizer specific to the black soil and the climate characteristics of Northeast China, we isolated five plant rhizosphere-promoting bacteria (PGPR), named as MZ1, MZ2, MZ3, MZ4 and MZ5, with different degrees of biological functions such as IAA synthesis, phosphate-solubilizing, potassium-solubilizing and siderophore-releasing, from the rhizosphere of maize field. The analysis of ecological adaptability showed that those five strains differed in salt resistance, drought tolerance, acid and alkali resistance, pesticide resistance. The 16S rRNA gene sequences analysis showed that the strains MZ1, MZ2, MZ3, MZ4 and MZ5 belonged to the genus of Sphingomonas, Enterobacter, Pseudomonas, Bacillus and Rhizobium, respectively. In maize field experiment with 50% nitrogen fertilizer reduction, the inoculation with MZ1, MZ3 and MZ5 increased grain yield by 19.9%-25.0%. MZ1, MZ3, and MZ5 could be used as microbial fertilizers for maize in Northeast China.