Feather waste rich in keratin is a potential high-quality protein resource, but effective recycling methods are lacking. Keratinase is considered to be a promising method for recycling waste keratin because of its ability to hydrolyze feather waste to produce high-value hydrolysates such as amino acids and peptides. However, the low disulfide reduction activity restricted the hydrolysis efficiency of keratinase on feathers. In this study, disulfide reductase was introduced to reduce the disulfide bond of feather keratin, and the degradation process of feather waste was accelerated by the synergistic action of highly active disulfide reductase and keratinase. First, four disulfide reductases derived from Bacillus subtilis 168 were heterologously expressed in Bacillus subtilis WB600, and their enzymatic properties were characterized. Furthermore, the extracellular expression of the disulfide reductase MsrA was increased by optimizing the signal peptide. Finally, the system for the synergistic degradation of feathers by disulfide reductase and keratinase KerZ1 was optimized, and the soluble proteins and amino acids in the hydrolysate were analyzed. The disulfide reductases AhpC, DLD, MsrA and TrxR were successfully extracellularly expressed with specific activities of 0.53, 1.69, 16.7, and 2.06 U/mg, respectively. When MsrA carried the signal peptide YxkH, the activity of extracellular disulfide reductase increased by 4.2 times. The soluble protein content in the hydrolysate obtained from the degradation of feathers by MsrA+KerZ1 was 3 times than that of KerZ1 alone. The optimized MsrA+KerZ1 degraded 100 g/L duck feather and chicken feather to produce 7 472.33 and 5 589.67 mg/L amino acids in the hydrolysate. In addition, corn plants watered with feather hydrolysate had thicker stems and more developed root systems, indicating that the nutrients in the hydrolysate could significantly promote plant growth. In conclusion, disulfide reductase can accelerate the efficiency of keratinase to degrade feathers, and the synergistic degradation system with keratinase lays a foundation for the efficient recovery of feather waste.
ZHANG Baoyu
,
PENG Zheng
,
ZHANG Juan
,
LI Jianghua
. Heterologous expression and optimization of disulfide reductase, and its application in assisting keratinase to degrade feather waste[J]. Food and Fermentation Industries, 2023
, 49(6)
: 42
-49
.
DOI: 10.13995/j.cnki.11-1802/ts.032344
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