The present study aimed to optimize the processing technology of natto fermented with Bacillus subtilis natto and Limosilactobacillus fermentum 2-2 and its effect on quality characteristics as well as volatile compounds. The results of single-factor tests and response surface methodology (RSM) showed that the optimal fermentation conditions of natto were L. fermentum inoculation amount of 0.3 %, fermentation temperature at 39 °C, fermentation time of 48 h, and after-ripening time of 24 h. Compared with natto control with B. subtilis natto only, natto co-cultured with B. subtilis natto and L. fermentum 2-2 showed higher scavenging ability of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and greater nattokinase activity. Volatomics analysis revealed that 71 differential volatile compounds were identified with 23 up-regulated and 48 down-regulated. Especially, co-fermentation of B. subtilis natto and L. fermentum 2-2 increased generation of alcohols, ketones and esters while reduced pyrazines formation. The above results indicate that co-culture of B. subtilis natto and L. fermentum can enhance the antioxidant and nattokinase activity and modify the volatile profile in natto and have the potential for application as the mixed starter in natto production.

Journal of Animal Science and Technology (JAST) is a peer-reviewed, open access journal publishing original research, review articles and notes in all fields of animal science. Topics covered by the journal include: genetics and breeding, physiology, nutrition of monogastric animals, nutrition of ruminants, animal products (milk, meat, eggs and their by-products) and their processing, grasslands and roughages, livestock environment, animal biotechnology, animal behavior and welfare.

This study aimed to investigate in vitro effects of the selected prebiotics alone, and in combination with two potential probiotic Lactobacillus strains on the microbial composition of Apis cerana gut microbiota and acid production. Four prebiotics, inulin, fructo-oligosaccharides, xylo-oligosaccharides, and isomalto-oligosaccharides were chosen, and glucose served as the carbon source. Supplementation of this four prebiotics increased numbers of Bifidobacterium and lactic acid bacteria while decreasing the pH value of in vitro fermentation broth inoculated with A. cerana gut microbiota compared to glucose. Then, two potential probiotics derived from A. cerana gut at different dosages, Lactobacillus helveticus KM7 and Limosilactobacillus reuteri LP4 were added with isomalto-oligosaccharides in fermentation broth inoculated with A. cerana gut microbiota, respectively. The most pronounced impact was observed with isomalto-oligosaccharides. Compared to isomalto-oligosaccharides alone, the combination of isomalto-oligosaccharides with both lactobacilli strains induced the growth of Bifidobacterium, LAB, and total bacteria and reduced the proliferation of Enterococcus and fungi. Consistent with these results, the altered metabolic activity was observed as lowered pH in in vitro culture of gut microbiota supplemented with isomalto-oligosaccharides and lactobacilli strains. The symbiotic impact varied with the types and concentration of Lactobacillus strains and fermentation time. The more effective ability was observed with IMO combined with L. helveticus KM7. These results suggested that isomalto-oligosaccharides could be a potential prebiotic and symbiotic with certain lactobacilli strains on A. cerana gut microbiota.