Study on bioactive peptide preparation from walnut meal by solid-state fermentation and its anti-oxidative activity

In order to take full advantage of walnut meal, the solid-state fermentation of walnut meal (WM) by Aspergillus niger was studied to evaluate the influence of inoculation quantity, temperature, water content of WM and time on the yield of bioactive peptide. Optimal solid state fermentation conditions obtained from response surface methodology were inoculated with 5.5% of Aspergillus niger, fermented at 33.50℃ for 84h and water content of WM 1.00mL/g. Under optimal conditions, the yield of peptide could reach 35.68% , which increased 26.7% over pre-optimization. The results also showed that the bioactive peptide had strong scavenging capabilities on DPPH, hydroxyl and superoxide anion free radicals with IC 50 values of 0.15, 1.75 and 2.4mg/mL. It was concluded that walnut meal is a good source for producing anti-oxidative peptide and the peptide is an ideally natural antioxidant.