Characterization Of High-efficiency Feather-degrading Strains And Its Degradation Mechanism

Millions of tons of feather waste are generated worldwide each year,and most of them are not properly recycled,which not only produces environmental pollution,but also causes great waste to feather,a high-protein biological resource.Therefore,the recycling of waste feathers is receiving more and more attention.From the perspective of microorganisms,this paper explores the use of biological methods to degrade waste feathers and convert them into high-value-added feed protein resources.At the same time,it explores the specific mechanism of efficient degradation of feathers by related strains.In this paper,we first performed heterologous expression of keratinase,and successfully obtained three keratinase-producing Bacillus subtilis engineering strains.B.subtilis WB600-p MA5q-ker K showed the highest keratinase activity by fermentation,reaching 982.26 U/m L,but Subsequent experiments have shown that a single keratinase cannot degrade natural feathers and requires a reducing agent and keratinase to work together.Based on this,the research team obtained a new feather-degrading microorganism from a long-term accumulation of soil from poultry feather waste through a large number of separations and screenings,which can completely degrade chicken feathers?including feather shafts?within 36 hours.The strain was characterized and identified from the morphological,physiological,biochemical and molecular levels,and the screened high-efficiency feather-degrading strain was named Streptomyces sp.SCUT-3.Subsequently,the preliminary application test of SCUT-3 degraded feather products in animals,plants and microorganisms was carried out.Feather degradation products can partially replace fish meal as an animal feed protein source,which can promote the growth of plants and increase the enzyme production of microbial engineering strains.In order to study the mechanism of high-efficiency degradation of feathers by this strain,the research team selected three strains of Streptomyces that are closely related to the test strain to conduct preliminary research on the mechanism of feather degradation.Scanning electron microscopy and agar penetration experiments at the same time confirmed that the mechanical force of hypha played an important role in the degradation of feathers by Streptomyces.Reducing power experiments show that disulfide bonds can be reduced only in the presence of intact bacteria,which may be related to the redox system on the cell membrane surface.The presence of free sulfhydryl groups was found during the degradation of feathers by Streptomyces,indicating that the disulfide bonds of natural feathers were opened.It was found through experiments that the reducing agent of sulfite was present in the fermentation supernatant of this strain.On this basis,in order to further explore the related mechanism of efficient degradation of feathers by Streptomyces at the molecular level,a comparative transcriptome sequencing of this strain was performed.Transcriptomics analysis showed that 1,459 genes were significantly differentially expressed,of which 871 genes were significantly up-regulated and588 genes were significantly down-regulated.Significantly different genes were annotated for GO function,among which the cellular process,metabolic process,single activity process,catalytic activity,cell membrane-related,and transport activity-related functions had the largest number of genes.Among them,transmembrane transport activity,ABC transport activity,and gene enrichment related to peptide and amino acid transmembrane transport activity are more significant.Analysis of the KEGG metabolic pathway showed that quorum sensing,amino acid metabolism,ABC transport system,oxidative phosphorylation,and fatty acid metabolism all have very significant up-regulated expression.Transcriptome analysis and experimental measurements indicate that sulfite and thiol compounds provides the reducing power of SCUT-3 to degrade feathers.Transcriptome analysis also found that oxygen and Fe²⁺can also significantly affect SCUT-3 degradation of feathers.Ten genes that may be related to feather degradation were selected from the significantly different genes,including genes related to sulfite production and transport pathways,genes related to MSH production and transport pathways,and protease genes for q RT-PCR verification.The results are consistent with the RNA-Seq results.In this paper,the whole genome sequencing and transcriptome sequencing of Streptomyces sp.SCUT-3 are performed for the first time.Based on this,a composite mechanism for degrading chicken feathers is proposed.The efficient degradation of feathers by Streptomyces sp.SCUT-3 is not a single factor,including mycelium machinery.The combined effect of stress,sulfite and thiol compounds reducing power and proteolytic hydrolysis.The results of our research will help further understand the degradation mechanism of keratin by Streptomyces,and provide theoretical support for the research on the hydrolysis process of feathers.