In order to improve the added value of soybean meal and other byproducts, the strain YSJB-30 was used to prepare for the probiotic agents of fermented feed, which had a big inhibition zone and strong proteolytic. With corn straw, rice hulls, defatted soymeal as raw material and considering the price of raw materials, we selected the optimum ratio of raw materials based on the living cell quantity. Plackett-Burman design was used to evaluate the influence of related 8 factors. Steepest ascent path was adopted to approach the optimal region. Then the Box-Behnken design and response surface analysis were used to determine the optimal levels of the main factors. It showed that three factors played the important roles in the medium, including the initial pH, fermentation temperature and processing of water. Under op timized culture conditions: initial pH 7.0, fermentation temperature of 36 °C, additive volumn of water 70%, K2HPO4 1.2%, MgSO4 0.06%, corn steep liquor 0.75%, glucose 1.5%, (NH4)2SO4 0.5%, fermentation time for 36 h, the living Bacillus subtilis cells reached 5.35×109 CFU/g. © 2016, Editorial Office of Journal of CIFST. All right reserved.
