Abstract: Rapeseed meal was used to produce peptide with Bacillus subtilis by solid-state fermentation. Taking rapeseed peptide yield as well as indexes soluble nitrogen and amino acid nitrogen,the medium conditions,such as initial pH,solid-liquid ratio,glucose concentration and KH2PO4 concentration were investigated by single factor test,and then the regression equation on rapeseed peptide yield versus the above mentioned factors was established to optimize the medium conditions. Results showed that the optimal conditions are as follows:solid-liquid ratio 1:2.35,initial pH 6.5 and concentrations of both glucose and KH2PO4 2.6 %. Under these conditions,rapeseed peptide yield reaches 11.43 % in theory .The measurement results of molecular weight distribution of rapeseed protein peptide in fermentation liquor showed that some new low molecular weight rapeseed peptides are produced during solid-state fermentation.

Key words: Bacillus subtilis, solid-state fermentation, rapeseed peptide, response surface methodology