Hygienic utilization of Bacillus tequilensis and waste spinach effluent for yielding valuable products from rice straw

Rice straw, containing harmful bacteria and being of low value, created a significant issue that limits its use. This study aimed to improve hygienic quality of fermented rice straw and create value-added products (α-tocopherol or organic acids) using Bacillus tequilensis QH1 (QH), waste spinach effluent (S), and their combination (QHS) for short- (7 day) and long-term (42 day) fermentation, without treatment as a control (CK). Long-term fermentation and QH reduced relative abundance of pathogenic and saprophytic Staphylococcus saparophytics from 53.9% to 5.24% and 12.6% and Enterobacter sp. from 4.34% to 1.75% and 0.43%. B. tequilensis QH1 secreted endoglucanase (42.20 U/g), β-glucosidase (27.27 U/g), cellobiohydrolase (44.52 U/g), and laccase (17.2 U/g) and facilitated degradation of hemicellulose and lignin. The QHS increased organic acids production by 63.7% on day 7 over the CK. Yields of α-tocopherol were higher in QH and QHS, at 1.39 and 1.46 times more than raw material (7.24 mg/kg DM), due to up-regulating biosynthesis of phenylalanine, tyrosine, and tryptophan. The S decreased α-tocopherol yield, and QH motivated B. cellulasensis emergence and together degraded lignin to synthesize α-tocopherol. In conclusion, utilizing combination of B. tequilensis QH1 and waste spinach effluent to produce hygienic and value-added rice straw was feasible. • Rice straw had poor hygiene due to containing pathogenic and saprophytic bacteria. • Pathogenic and saprophytic bacteria was reduced by QH at long-term fermentation. • B. cellulasensis and B. tequilensis QH1 degraded lignin to yield α-tocopherol. • Productions of organic acid and α-tocopherol were increased by QHS.