Test of Antioxidants and Alpha-glucosidase Inhibitors from Lactic Acid Bacteria in Fermentation of Soy Milk (Soygurt)

Abstract

Soygurt is an innovative product from yogurt which is fermented from soy milk. This research is an experimental study performed by an in vivo approach. The disc diffusion method evaluated the antibacterial activity of lactic acid bacteria isolates from Soygurt. Meanwhile, the antioxidant activity and inhibition of α-glucosidase enzymes were evaluated from cell-free supernatants of lactic acid bacteria isolated by spectroscopic methods. The results of the enumeration of lactic acid bacteria in Soygurt with 5% Lactobacillus acidophilic yogurt starter were 8.00 x 104 CFU/ml, and the calculation of lactic acid bacteria in Soygurt with Yakult starter was 5.00 x 107 CFU/ml. Lactic acid bacteria isolates from Soygurt with 5% Lactobacillus acidophilic starter showed no antibacterial activities against Staphylococcus aureus bacteria by the disc diffusion method. However, this lactic acid bacteria isolate had antioxidant activity and inhibited the α-glucosidase enzyme. It was shown by the percentage of DPPH inhibition, which ranges from 27.06-58.63%. Meanwhile, the moderate inhibitory activity of the α-glucosidase enzyme was 50.55%. Therefore, it can be concluded that lactic acid bacteria isolated from Soygurt with 5% Lactobacillus acidophilic yogurt starter have antioxidant and antidiabetic activity.