Keratinase Production by Bacillus sp. MD24 in Sub-merge and Solid State Fermentation

Abstract

Chicken feathers are valuable solid waste that mainly contains insoluble proteins called keratin. Naturally, keratin is degraded by microbes that produce a specific protease called keratinase.  Many reports have been addressed to study Bacillus species as keratin-degrading microbes. However, most reported works were using pathogenic soil Bacillus. Our work has been concentrated on keratinase produced by a soil bacterium, Bacillus sp. MD24 and we confirmed it as a non-pathogenic bacterium. This report describes the different profiles of keratinase fermentation between sub-merged fermentation (SmF) and solid-state fermentation (SSF) using chicken feathers as a sole carbon and nitrogen source.  Keratinase production and weight loss were followed for 10 consecutive days, the keratinase molecular weight was investigated, the type and concentration of 18 amino acids were determined using LC-MS/MS after 10 days to seek its potential as the amino acid source, and protein by-product concentration was measured. The results showed that keratinase production as well as weight loss in SmF was better compared to SSF with different optimum production times. Surprisingly, L-arginine was a dominant amino acid in SmF hydrolysate which contained 42.06% of total amino acids and made Bacillus sp. MD24 is a potential organism for L-arginine production. As protein by-product concentration was relatively low in both conditions showing effective utilization of chicken feathers as matter and energy source, consequently, cell-free keratinase should be applied to degrade chicken feathers into valuable materials.