A novel steam explosion sterilization improving solid-state fermentation performance

Traditional sterilization of solid medium (SM) requires lengthy time, degrades nutrients, and even sterilizes inadequately compared with that of liquid medium due to its low thermal conductivity. A novel sterilization strategy, high-temperature and short-time steam explosion (SE), was exploited for SM sterilization in this study. Results showed that SE conditions for complete sterilization were 172 degrees C for 2 min and 128 degrees C for 5 min. Glucose and xylose contents in medium after SE sterilization increased by 157% and 93% respectively compared with those after conventional sterilization (121 degrees C, 20 min) while fermentation inhibitors were not detected. FTIR spectra revealed that the mild SE conditions helped to release monosaccharides from the polysaccharides. Bacillus subtilis fermentation productivity on medium after SE sterilization was 3.83 times of that after conventional sterilization. Therefore, SE shortened sterilization time and improved SM nutrition, which facilitated fermentability of SM and should promote economy of solid-state fermentation. (C) 2015 Elsevier Ltd. All rights reserved.