Changes of protein in natto (a fermented soybean food) affected by fermenting time

Abstract

The purpose of this study was to investigate effect of fermentation time on the proteins of steamed soybean inoculated with Bacillus subtilis (natto). The result was found that the contents of trichloroacetic acid soluble nitrogen (TCA-N) and drgree of hydrolysis (DH) of protein increased with the fermentation time increased, but the protein solubility was declined with increasing the fermentation time in advance, then increased. The most bands of soy proteins were found to disappear from the Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) electrophoretogram after 24 h of fermentation. Some of nonessential amino acids were found to remarkedly decline, but some of them were remained unchanged after 24-48 h of fermentation., However the most essential amino acids were found to declined after 36h of fermentation, then all of them increased after 48 h of fermentation except histidine.