Co-expression of protease and pectinase in Bacillus subtilis using the herbal saponin extract as substrate

This study armed to determine the expression of protease and pectinase in Bacillus subtilis using the herbal saponin extract as the fermentation substrates and then characterize the fermentation broths. The saponin concentration in the crude extract from four herbs reached to 25% under the extraction conditions of 60 °C, with a pH 9 for 3 h at a solid-liquid ratio of 1:18. In direct fermentation of Bacillus subtilis in the saponin extract, the maximum activities of protease and pectinase in the cell supernatant reached 3984 and 227 U/ml, respectively. Correspondingly, when 5% glucose was added to this extract for the fermentation, the two maximum activities were up to 2451 and 1390 U/ml, respectively. When characterization of the two abovementioned fermentation broths was carried out, it was observed that the luminousness values were increased to 26.9 and 39.2% from 9.7% of the initial value after 32 h of fermentation, respectively, and there was no significant change in the saponin concentration during the fermentation processes. The evaluation values of washing performance were remarkably improved by 8.2 and 21.7%, respectively.