Effects of Bacillus subtilis on Degradation of Cellulose

Bacillus subtilis is a representative probiotic widely used in food, medicine, livestock and other industries. In this experiment a strain of Bacillus subtilis was isolated and identified, and its ability to degrade cellulose was also measured. The results showed that Bacillus subtilis had strong capacity to degrade cellulose（62.3% was degraded） and weak capacity to degrade hemicellulose（17.2% was degraded）, while it could hardly degrade lignin. The total protein amount in the fermentation medium with cellulose-rich substrate reached by 9.4% after Bacillus subtilis fermentation, compared with that without cellulose-rich substrate. Furthermore, the amounts of Met, Lys and Leu reached by 31.4%, 42.2% and 4.9%, respectively. At 36 h of fermentation, the activity of cellulase reached the highest, and at this time the activity of the enzyme was obtained at 7.19 U · mL-1. The mRNA expression level of the cellulase gene was detected by qPCR, and the experimental group with cellulose substrate was about 2.5 times more than that of the non-cellulose substrate control group. These above results demonstrated that this strain of Bacillus subtilis had a strong ability to degrade cellulose, and synthesize more proteins and restrictive essential amino acids. This study revealed that Bacillus subtilis was a new alternative to ferment cellulose substrates to produce commercial feed or feed additives.