Optimization of Solid-State Fermentation Conditions of Quercus liaotungensis by Bacillus subtilis

Abstract

The current study aimed to investigate the solid-state fermentation process of Quercus liaotungensis (QL) by Bacillus subtilis (BS). The parameters included the inoculation amount, the soybean meal addition amount, the fermentation temperature and the ratio of material to water. The optimal process was determined based on the nutritional value, tannin content and DPPH clearance of QL after fermentation. The results showed that: (1) The parameters of the optimal process included inoculating 106 BS per gram of QL, then adding 10% soybean meal, the ratio of material to the water of 100:80, and temperature at 33 °C for 72 h. (2) In the optimum fermentation conditions, the crude fiber content, and the ether extract content of QL decreased by 66.94% and 66.96%, respectively (p < 0.05). Moreover, the crude protein content and the ash content increased by 65.81% and 4.63%, respectively, after fermentation (p < 0.05). Additionally, the tannin content decreased by 62.77% (p < 0.05), and the DPPH scavenging rate decreased by 45.45% (p < 0.05) after fermentation, respectively. In summary, the QL significantly improved the nutritional value after the solid-state fermentation with BS.