Screening, Identification And Optimization Of Fermentation Condition Of Feather-degrading Bacteria

Feathers wastes locks up abundant of keratin, which could be converted to useful protein and amino acids. The processing including physical and chemical methods will cause great environmental pollution problems. The enzymatic hydrolysis by microorganisms can avoid the environmental pollution, and it can be effectively converted feathers to available protein.Two feather-degrading strains GZD-23and LFJ-11were isolated from soil which produced higher feather-degrading activity. And the strains could utilize feather as the sole carbon source to grow. Based on the detailed analysis of morphologica,physiological-biochemical properties and16S rDNA sequencing, the strains GZD-23and LFJ-11was identified as Bacillus megaterium and Bacillus megatherium. It was the first time Bacillus megatherium was reported to be able to degrade feather.The fermentation conditions for crude keratinase production of strains GZD-23and LFJ-11were investigated.The properties of crude keratinase from strains GZD-23and LFJ-11were investigated.The optimal feather-degradation conditions for fermentation by strain GZD-23were as followed pH8; temperature of30℃; shaking rate100rpm; inoculum size of7%; feather20g/L; Addition of sucrose and peptone to the feather medium, the enzyme production was increased by50%and23.7%; liquid loading has little effect on the ability of enzyme production.The properties of crude keratinase from strain GZD-23as follows:Maximum keratinase activity was achieved at60℃,pH7.5.The enzyme was inhibited by Cu2+、Hg2+、Fe2+、Co2+、Zn2+、Mn2+、SDS、EDTA and β-mercaptoethaonl (0.5%).The enzyme was stimulated by TritonX-100(0.1%)、 DMSO、Isopropanol (1%)、Acetonitrile (5%)、β-mercaptoethaonl (0.1%) Kinetic studies showed that Km of keratinase of GZD-23strain were1.03mg/mL.The optimal feather-degradation conditions for fermentation by strain LFJ-11were as followed:pH7; temperature of37℃; shaking rate100rpm; inoculum size7%; feather is15g/L;liquid loading has little effect on the ability of enzyme production; Addition of glucose and NaNO3to the feather medium, the enzyme production was7.3-fold and4.7-fold higher than the yield in the basal feather medium.The properties of crude keratinase from strain LFJ-11as follows:Maximum keratinase activity was achieved at60℃,pH10.The enzyme was inhibited by Cu2+、Hg2+、Fe2+、Co2+、Zn2+、EDTA、SDS、Acetonitrile (5%) and β-mercaptoethaonl (0.1%);The enzyme was stimulated by Na+、TritonX-100、 DMSO (1%)、β-mercaptoethaonl (0.1%). Kinetic studies showed that Km of keratinase of LFJ-11strain were1.23mg/mL.These results make these keratinases from strains GZD-23and LFJ-11 interesting for application in detergent formulations in leather processing, and in other processes involving keratin wastes hydrolysis.