Optimization of Process Parameters of Hydrolyzed By-product of Combined Enzyme Down Processing

The aim of this study was to explore the optimal technological conditions for the synergistic enzymatic hydrolysis of feather processing by-products by recombinant keratinase and disulfide bond reductase from Bacillus licheniformis CP-16.Firstly,the appropriate proportion of keratinase and disulfide bond reductase was explored in this experiment.Secondly,the factors affecting the treatment of combined enzymes were studied,including steam pressure treatment time,enzymatic hydrolysis time,combined enzyme addition level and water content.Finally,L9(3⁴) orthogonal test was used to further optimize the processing conditions.The results were as follows:When the enzyme activity ratio of keratinase and disulfide bond reductase was 80：1 and the final concentration of keratinase was 90 U/mL,the combined enzyme had the best efficiency in feather hydrolysis.Pressure treatment of feather keratin for 2 h was more conducive to hydrolysis of feathers processing by-products by combined enzymes.Feather hydrolysis rate was the highest at 60 h hydrolysis,but it was not significantly different from that at 48 h (P>0.05).The efficiency of feather enzymatic hydrolysis in the total reaction system with 5.5 mL buffer was significantly higher than control group(P<0.05),but the difference was not significant compare to the group with 4.5 mL buffer (P>0.05).The results of orthogonal test showed that,the factors affecting the hydrolysis efficiency were pressure treatment time,enzymolysis time and enzyme dosage from large to small.The optimal conditions for feather enzymatic hydrolysis were:The ratio of keratinase to disulphide bond reductase was 80：1,121 ℃ for 2 h,the final concentration of keratinase was 90 U/mL,and the enzymatic hydrolysis was conducted at 50 ℃ for 48 h.At this condition,the soluble protein content of supernatant produced of each gram feather was 352.72 mg,which was 640.26% higher than that of the control group.In conclusion,the combination of multiple treatment processes was more conducive to improving the efficiency of hydrolysis of feathers processing by-products by combined enzymes.The study could provide guidance for the development and utilization of feather resources.