To reduce the high cost caused by steam sterilization of fermentation substrates and equipments in mesophilic
solid-state fermentation of rapeseed meal (RM), a thermophilic protease-producing strain RM-2 from RM was
isolated and employed in thermophilic solid-state fermentation of unsterilized RM for polypeptide preparation.
The isolate was identified as Geobacillus stearothermophilus by appearance of colonies and microscopic observation
as well as 16S rDNA sequencing. The highest yield of polypeptide (9.67%) was obtained by RM-2 at
50% moisture content, 55 °C and 24 h fermentation time. Analysis of microbial community diversity in fermented
RM revealed Geobacillus stearothermophilus as dominant strain inhibiting most mesophilic microorganisms.
Thermophilic solid-state fermentation on RM improved the yield of rapeseed polypeptide, as well as the
utilization rate of substrate. The application of this technology (thermophilic solid-state fermentation) would be
environmentally friendlier and energy-saving to industry. |
