Study on microbial protein and the mechanism of solid-state fermentation with periodical dynamic changes of air

Abstract

The effect of different extraction and purification conditions on the microbial protein obtained from solid-state fermentation (SSF) and the effect of periodical dynamic changes of air on protein have been studied. The mechanism of solid-state fermentation with periodical dynamic changes of air is also discussed. Compared with static solid-state fermentation, periodical dynamic changes of air afford a higher protein mass; from 1 g of the fermentation microbe, 5.3 mg of the intracellular protein (an increase of 34.63%) and 9.09 mg of the extracellular protein (an increase of 17.8%) were obtained on the sixth day of fermentation. The filter paper activity and carboxymethyl cellulose activity (FPA and CMCase) of the extracellular protein are 1.739 μmol/s and 109.592 μmol/s, respectively, which represent increases of 60.1% and 21.2% over the corresponding values for static solid-state fermentation. The FPA and CMCase of the intracellular protein are 0.245 μmol/s and 6.392 μmol/s, respectively, which represent decreases of 22.2% and 38.7% over the corresponding values for static solid-state fermentation. The enzyme activity of the microbial extracellular protein in solid-state fermentation with periodical dynamic changes of air on the fifth day is nearly equal to that on the sixth day without periodical dynamic changes of air, so the period of fermentation can be shortened. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) experiments suggest that pulsating air pressure stimulation leads to a decrease in the amount of protein component with molecule mass of about 80400Da, and an increase in the amount of protein component with molecule mass of about 28520Da.