Abstract
Keratinase producing microorganisms are being increasingly utilized for degradation and recycling of poultry feather waste. Two native strains BF11 (Bacillus subtilis) and BF21 (Bacillus cereus) degrading keratin completely were characterized. The native strains produced more than 10 KU/mL of enzyme. Strain improvement resulted in isolation of MBF11 and MBF21 from BF11 and BF21 isolates, respectively. Optimization of nutritional and physical parameters of these MBF isolates at laboratory scale increased the overall keratinase activity by 50-fold resulting in a yield of 518–520 KU/mL. Fermentation media designed with starch as carbon source and soya bean meal as nitrogen source supported high levels of enzyme production. The optimum conditions for enzyme production were determined to be pH 8.5 and temperatures of 45–55°C for MBF11 and 37°C for MBF21, respectively. Culture filtrate showed a significant increase in the amounts of cysteine, cystine, methionine, and total free amino acids during the fermentation period. The ratio of organic sulphur concentration was also considerably higher than that of the inorganic sulphate in the culture filtrate suggesting the hydrolysis of disulphide by the isolates.
Highlights
Feather is generated in bulk quantities as a by-product in the poultry industry globally
A total of 80 samples were analysed for potential keratinase producing organisms. 400 keratinophilic microorganisms were isolated, out of which 120 isolates exhibited keratinolytic activities
In the 16S rDNA typing and phylogenetic analysis (Figure 1), BF11 was designated as Bacillus subtilis and BF21 as Bacillus cereus
Summary
Feather is generated in bulk quantities as a by-product in the poultry industry globally. It is a very rich source of protein with β-keratin constituting 91% of feather protein. The bulk of feather waste is poorly recycled in nature and has limited utility due to the chemically unreactive nature of keratin This waste has been converted into feed supplement, resulting in feed of poor quality which is nonviable economically [3]. Recycling of this by-product is neither profitable nor environmentally friendly. The disposal of this waste is a global environmental issue leading to pollution of both air and underground water resources [4]
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