Study On The Screening Of Waste Feather-degrading Strain And The Characteristics Of Its Degradation

Feathers are keratinized derivatives of epidermal cells in bird and poultry animal.Feathers are as by-product at the poultry processing plant process.Feathers contain over 90%crude protein in a form of keratin,a hard protein.As the keratin is not easily degraded,the utilization rate of feathers are low.In China,millions of tons of feathers are thrown away and buried every year.This not only causes environmental pollution,but also lead to waste of protein resources.In addition,feather degradation methods commonly used in industrial production include high temperature and high pressure method,acid hydrolysis method,alkali hydrolysis method,oxidation reduction method and so on.However,these methods have the disadvantages of environmental pollution,high energy consumption,protein destruction,high cost,and low product utilization.Therefore,there is an urgent need that is environmentally friendly and efficient for a feather degradation method..Biological degradation of feathers can reduce environmental pollution and improve the utilization of degradation products.Biological degradation of feathers mainly includes microbial degradation of feathers and keratinase degradation of feathers.In this paper,microbial degradation of feathers was used.Two strains with highly efficient feather-degrading ability were isolated from the soil at the slaughterhouse waste dump.According to Bergey's Manual of Systematic Bacteriology,the isolated strains were identified based on morphologicalphysiological and biochemical indicators;the molecular biological identification of the strain was required to determine the species of isolated strains.Optimization of the fermentation conditions of the isolated strains;and the characteristics of feather degradation products at optimal fermentation conditions were also studied.The specific experimental contents and results are as follows:?1?This chapter uses the culture medium with feather powder as the only carbon source and nitrogen source for screening and identification of feather-degrading strains.The samples were respectively collected from different sites containing feathers,after the enrichment,preliminary screening,rescreening,separation and purification,10 strains of feather degrading strains were finally obtained,among them,the strains X-05 and X-07 were more effective than other strains in degrading feathers.The rate of feather weight loss at 48 h after X-05 and X-07 strains was 90%and 92%,respectively.Through morphological observation of X-05 and X-07 strains,physiological and biochemical indicators and molecular biological identification,they are Bacillus lincheniformis,Bacillus thuringiensis respectively.?2?Single-factor experiments,Plackett-Burma test and Box-Behnken response surface design were used to optimize the medium composition and fermentation conditions.It was found that the optimal fermentation conditions for sulfhydryl content X-05 strain:feather11g/L,MgSO₄ 0.10g/L,NaCl 0.50g/L,K₂HPO₄ 0.30g/L,KH₂PO₄ 0.40g/L,CaCl₂ 0.01g/L,initial pH 8.30,at 37.0?,the predicted value of sulfhydryl content is 1.84 mmol/L;X-07strain:feather 15g/L,MgSO₄ 0.10g/L,NaCl 0.50g/L,K₂HPO₄ 0.30g/L,KH2PO₄ 0.40g/L,CaCl₂ 0.01g/L,initial p H 8.40,at 39.0?,the predicted value of sulfhydryl content is 1.56mmol/L.?3?Under the optimized fermentation conditions,some characteristics of feather degradation products with the strains X-05,X-07 were studied.The results of determination of sulfhydryl content showed that the sulfhydryl content reached 1.80±0.23mmol/L at 48h with X-05 strain,which was 98%of the predicted value.The sulfhydryl content reached 1.49±0.13mmol at 48h with X-07 strain,which was 96%of the predicted valueWe also found that the plumes and pinna were mostly degraded after 24 h.After 48 h,the plume was left undegraded.At 72 h,there only had the skin of the plume was not degraded,and the central part was degraded with X-05 strain;Only one part of plume was left undegraded with X-07strain.