Improvement of S-allyl-L-cysteine content, probiotic properties and constipation prevention effect of black garlic by the lactic acid bacteria fermentation

In this study, 3 lactic acid bacteria strains, Lactiplantibacillus plantarum X7021, X7022 and Limosilactobacillus fermentum S1L23, which were isolated from the brine of stinky tofu, were used to ferment black garlic stuff supplemented with 2% (w/v) soy protein isolate. The viable cell count of all strains could increase about 2 lg CFU/mL after 20 h of growth. The S-allyl-L-cysteine (SAC) content was significantly improved about 3.2–4.5 folds after fermentation (p < 0.001). The highest SAC content of 61.3 μg/mL was achieved by the fermentation of L. plantarum X7022. Meanwhile, the fermentation significantly enhanced the in vitro and cellular antioxidant activities and angiotensin I converting enzyme inhibitory activity of black garlic. The fermentation also increased the antimicrobial activity against Helicobacter pylori and the fermented black garlic with L. plantarum X7022 played the strongest role. Finally, oral administration of the fermented black garlic with L. plantarum X7022 showed the prevention effects on the loperamide-induced constipation through significantly shortening the defecation time, defecation weight and peristalsis function. Accordingly, LAB fermentation is effective to endow the probiotic properties to black garlic, and the strain L. plantarum X7022 is a prospective starter.