Isolation of keratinase from bacterial isolates of poultry soil for waste degradation

Abstract

Isolation of two keratinolytic bacterial strains from poultry soil as well as purification and properties of keratinase were investigated. Isolates were designated as KI8101 and KI8102 (KI, keratin isolates) and were identified as Bacillus subtilis and B. licheniformis respectively. The purified enzyme from KI8102 exhibited a high specific activity of 500 U/mg with 71‐fold purification and 41% yield. SDS‐PAGE analysis indicated that the purified keratinase had a molecular mass of 32 kDa. The optimum temperature and pH were 50°C and 7.5, respectively. Its Km was 83.3 μM and Vmax was 71.4 μmol/mL min. The bacterium could potentially degrade keratin waste such as human hair, nails, bovine hair and wool. Therefore, the enzyme could improve the nutritional value of meat and poultry‐processing waste containing keratin and could be a potential candidate for biotechnological processing involving keratin hydrolysis.

In silico characterization of broad range proteases produced by Serratia marcescens EGD‐HP20

“…Goldstein et al observed that, Bacillus altitudinis GVC ‐11 was able to degrade white feathers within 48 h while only 50% degradation of colored feather was noted within 48 h. This delay in biodegradation of dark feathers was due to the presence of melanin pigment in dark/brown feathers. The fact that, melanin content in hairs and dark/brown feathers was responsible for low enzyme induction and degradability was also confirmed by Desai et al . The activity of keratinolytic protease was found to be higher in another strain of Bacillus , B. pumilus GRK (373 ± 4 U ml −1 ) when chicken feather was used as a substrate .…”

Isolation and Partial Characterization of an Antifungal Protein Produced by Bacillus licheniformis BS-3

“…It was found that the N -terminus of F2 protein is blocked. From molecular mass and characteristics of F2 protein, it seems to be similar to keratinase produced by B. licheniformis KI8102 [ 25 ], and a subtilisin-like alkaline serine proteinase from B. licheniformis RKK-04 [ 26 ]. The purified keratinase has a molecular mass of 32 kDa and its optimum temperature and pH are 50 °C and 7.5, respectively.…”

Biodegradation of Hard Keratins by Two Bacillus Strains

“…In the presented study, pig bristle and human hair were subjected to similar extent of biodegradation in short, four-day cultures, however B. polymyxa produced more keratinases on hair substrate while B. cereus on bristle. It appears that both strains were more adapted to utilization of keratin appendages with thick outer cuticle, which in pig bristle is formed of about 30 cell layers and 10 layers in human hair ( 18 ). Despite a single-layer cuticle, lamb wool was not an easily degradable and accessible substrate for the tested bacteria.…”

“…During experiments on B. licheniformis K18102, presented by Desai et al ( 18 ), comparative cultures on chicken feathers and other materials like bovine hair, wool, human hair and nails were investigated. The strain produced significant keratinolytic activity in the presence of all substrates, except human hair and nails, measured after thirteen days of culture.…”

“…According to Desai et al ( 18 ), wool represented a more digestible substrate for B. licheniformis than human hair. In our experiment involving B. polymyxa and B. cereus , lamb wool was nearly equally resistant to biodegradation and triggered comparable keratinase production, nevertheless it was more beneficial for the B. cereus strain.…”