Millions of tons of feather waste are generated from poultry farming as a potentially renewable and nitrogen-rich resource, and this is constantly increasing. Bioconversion is the most promising low-cost and environmentally friendly recycling method, while the efficiency of isolated natural feather-degrading bacteria (FDB) cannot meet the requirements of industrial use. The process of bacterial breakdown of feathers not only requires proteases, but also involves complex reduction mechanisms that are not yet known. Previous heterologous expression of keratinase genes in non-FDB hosts has had very limited success. In this study, the mechanism of sulfite production via the oxidation of cysteine ​​dioxygenase (CDO1) was first identified in Streptomyces sp. SCUT-3, which is important for the reduction of spring disulfide bonds. The precipitation of cdo1 significantly reduced the sulphite production (from 38.5 to 22.5 mg / l) and the feather degradation rate (from 45.7% to 39.5%) of SCUT-3 in 5% chicken feather medium (CFM) culture. The overexpression of cdo1 increased bacterial single cell sulfite production and feather protein conversion efficiency by 3.8 and 2.5 fold, respectively, on day 2 at 5% CFM. On this basis, a new strategy is proposed to increase the efficiency of feather degradation by improving the reducing power and keratinase activity of FDB according to its own feather degradation mechanism. Thus, co-overexpression of CDO1 and protease Sep39 successfully increased the conversion efficiency of SCUT-3 (42.5% higher than wild type) on day 2 in a 5% CFM culture. With the co-overexpression strain SCUT-Ocdo1sep39, 57.5% of the proteins in feathers were converted into soluble peptides and free amino acids (0.20 g and 0.29 g / g feathers) by solid-state fermentation in 6 days, which was 28.6% higher than in wild type -SCUT -3. The process developed here has a much higher economic benefit and a smaller ecological footprint than previously reported processes for feather processing and is powerful for the industrial recycling of feather waste. This study also elucidates the disulfide bond mechanism of FDB and provides a reference for further genetic modifications of FDB.

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