Screening And Fermentation Conditions Optimizing Of A Feather-degrading Strain And Its Characterization Of Degradation

Feathers with high protein are by-products of poultry processing.A large number of waste feathers are generated annually,which caused environmental contamination because of their low degradation and utilization.Microbial degradation of feathers can protect the environment as well as utilize the wastes,and have the remarkable social and economic benefit.In this paper,a strain with highly efficient feather-degrading ability was isolated from the soil,which species was identified.Fermentation conditions influencing on feather degradation and characterization of degradation were investigated.The results can provide a theoretical basis for the further use of feathers.The main results are reported as follows:1.A feather-degrading strain with higher efficiency was isolated from four different sources of soil samples by preliminary screening and secondary screening in sequence,named H3.The strain H3 was identified as Bacillus cereus based on morphological,physiochemical characteristics and 16 S rRNA gene analysis,which named as Bacillus cereus H3.And a phylogenetic tree was constructed.An Accession Number KX548899 was gained after the information of gene of strain H3 was submitted to NCBI.2.Fermentation conditions influencing feather degradation of Bacillus cereus H3 were investigated using chicken feathers as the sole carbon source by single-factor experiments,PB tests and Box-Behnken response surface design.The optimal conditions with the target of soluble protein content have been obtained as follows:(1)for medium,feather content 20 g/L,inorganic salt NaCl 0.1 g/L,MgSO4 0.1 g/L and KH2PO4/K2HPO4 0.7/1.4 g/L;(2)for fermentation conditions,culture volume 50mL/250 m L,inoculation amount 3%,initial pH value 10.47 and culture temperature 30.99 ?.The yield of soluble protein was 4.8 times higher than that before optimization.3.Characterization of degradation was researched under the optimal fermentation conditions.The result showed that the maximum soluble protein and keratinase activity reached the maximum at same time.Amino acid content obtained the highest level after 6 days of fermentation,which contains 4 kinds of essential amino acids with highest content of phenylalanine.Antioxidant in vitro assays showed that feather fermentation broth had excellent antioxidant activities.Infrared analysis showed that the fermentation hydrolyzate was composed of polypeptides.The microcosmic change of feather structure was investigated by SEM.The result showed that feather degradation usually started from disintegration of barbules,and degraded completely with surface breakdown of feather barbules and shaft.