Abstract:

In the solid-state fermentation process of rapeseed meal by Bacillus.subtilis 10160, nitrogen solubility index, amino acid nitrogen, protease activity and peptide content in fermentation liquid were measured at intervals of 0.5 h, and antioxidant activities of produced paptides were evaluated by various assays, including DPPPH radical scavenging, superoxide anion radical scavenging and hydroxyl radical scavenging. Results showed that protease activity, nitrogen solubility index and peptide content all exhibited a tendency to first increase and then decrease as prolonging of fermentation time and reached peak values at mid-fermentation (3d), which were 1840 U/ml, 70% and 7.5 mg/ml respectively. A positive correlation was found between free radical-scavenging activities and concentration of rapeseed peptides, and the scavenging rates against DPPPH radicals, superoxide anion radicals and hydroxyl radicals were 88.5%, 71.2% and 83.1%, respectively at concentration of 7.5 mg/ml. Gel filtration chromatographic analysis showed that a lot of low molecular weight peptides were produced at mid-fermentation. Peptides of lower molecular weight had stronger free radical-scavenging activities.

Key words: solid-state fermentation, rapeseed peptide , free radical scavenging activity