Steam explosion pretreatment coupling high-temperature short-time sterilization facilitating cellulose degradation and sporulation-regulatory gene expression in high-solid fermentation.

Steam explosion coupling high-temperature short-time sterilization (SE-HTST) was exploited to modify cellulosic biomass medium properties and promote high-solid fermentation (HSF). Biomass characterization analysis showed that SE-HTST enlarged microstructural pores and cavities in solid media, providing more effective space for microbial growth. Meanwhile, SE-HTST helped to release glucose from the cellulose with 35.8 ± 4.5, 20.0 ± 2.3, and 12.3 ± 5.7 mg glucose/g dry medium at 24, 48, and 72 h of fermentation, which were 3.1, 2.3, and 1.5 times higher than that in medium from conventional thermal sterilization (CTS), respectively. SE-HTST increased the viable cell and spore number of Bacillus subtilis by 1.8 and 1.6 times at 72 h of fermentation compared to CTS. Moreover, the expressions of master transcriptional gene spo0A and the early sigma factors of sigF and sigE genes gradually increased in the SE-HTST medium, showing enhanced sporulation in HSF. Therefore, SE-HTST is an effective strategy for facilitating cellulose degradation, improving glucose nutrients in biomass medium, and promoting sporulation-regulatory gene expression during high-solid fermentation, which enhances the production of microbial ecological agents using B. subtilis significantly. • SE-HTST facilitated cellulose degradation and improved nutrients in biomass media. • High levels of spo0A, sigF, and sigE expression with SE-HTST indicated enhanced sporulation. • SE-HTST presented a porous medium and effective contact space for microbial cells. • The proposed model well elucidated microstructural changes of cellulosic biomass media. • SE-HTST improved biomass medium properties and facilitated fermentation performance. [ABSTRACT FROM AUTHOR]