OPTIMIZED LACTOBACILLUS PLANTARUM LP6 SOLID-STATE FERMENTATION AND PROTEOLYTIC HYDROLYSIS IMPROVE SOME NUTRITIONAL ATTRIBUTES OF SOYBEAN PROTEIN MEAL

The solid-state fermentation of soybean protein meal (SPM) by Lactobacillus plantarum Lp6 was studied to evaluate the influence of soluble starch, acid protease and time on the degree of hydrolysis (DH) and viable cell counts (VCC). The fermented SPM (FSPM) was optimized for maximum DH and VCC using response surface methodology. The optimum conditions determined were the following: soluble starch (0.4 g/g of SPM), acid protease (0.1 g/g of SPM) and time (66 h). The optimized values were 22.58% and 9.08 (log cfu/g) for DH and VCC, respectively. Fermentation using the optimized process conditions increased the amount of low molecular weight peptides (<20 kDa) compared to SPM with high molecular weight polypeptides (>97.4 kDa). The protein content (60.15%) of FSPM increased following fermentation of SPM. The free amino acids profile (0.32 to 8.03 g/100 g protein) and protein solubility (29.33% to 38.35%) increased significantly (P < 0.01) during fermentation due to the hydrolytic actions of L. plantarum Lp6 and acid protease.