Abstract:

In order to develop a strategy for reducing hexavalent chromium Cr(VI) in heavy metals, feather fermentation with Bacillus subtilis CH-1 was conducted to produce feather fermentation liquid (FFB). The high toxicity of Cr(VI) was reduced to low toxicity trivalent chromium using the abundant cysteine in FFB. The activity of β-keratinase, concentration of cysteine and reduction rate of Cr(VI) in FFB were determined. In FFB, the maximum β-keratinase activity of FFB was reached at about 21st hour, the highest cysteine concentration was reached at 36th hour, and the optimal time for Cr(VI) reduction was also 36 hours. The reduction effect of FFB on Cr(VI) was not affected by high pressure and high temperature treatment, indicating that no biological enzymes were involved in the reduction process. Furthermore, when the FFB supernatant stock solution was concentrated 5 times and then treated with potassium dichromate solution, it was found that the reduction effect of the concentrated solution was 1.5 times that of the original supernatant. These results show that Bacillus subtilis CH-1 can effectively degrade feather waste, and the hydrolysate contains a large amount of cysteine, which has a strong reduction effect on Cr(VI). The present study provides a candidate strain and accurate theoretical basis for the pollution-free treatment and utilization of feather waste, which has a good application prospect and value in circular agro-ecosystem.

Key words: Cr(Ⅵ) reduction, feather hydrolysate, Bacillus subtilis CH-1, keratinase activity, L-cysteine, environmental governance