Improving thermal fermentation and production of Bacillus subtilis from lignocellulosic hydrolysate by glycerol protection

Abstract Bacillus subtilis prebiotic is a promising alternative to antibiotics, offering advantages in animal wellbeing and the utilization of abundant raw materials. To align with the enzyme hydrolysis processing temperature of lignocellulose materials, typically 45–50 ℃, it is essential to enhance the temperature tolerance of Bacillus subtilis as much as possible. Based on the comparison of varied protectants, a glycerol-protecting method was established to effectively improve the thermal fermentation performance. Comprehensive evaluation metrics, such as cell dry weight and viable bacterial count, were used to determine the optimal fermentation conditions for B. subtilis at 50 ℃, which included 70 g/L of glucose substrate and 1% v/v glycerol protection. To validate the practicality of this approach, the glycerol protection fermentation was further applied in lignocellulose hydrolysate, resulting in a yield of 22.43 g/L of B. subtilis, which is an increase of 20.9%, corresponding to a yield of 0.43 g/g. This study presents a feasible and systematic approach to develop thermal fermentation and production of Bacillus subtilis prebiotic from lignocellulose biorefinery.