Biodegradation of feather waste by keratinase produced from newly isolated Bacillus licheniformis ALW1

Abstract

Keratinase are proteolytic enzymes which have gained much attention to convert keratinous wastes that cause huge environmental pollution problems. Ten microbial isolates were screened for their keratinase production. The most potent isolate produce 25.2 U/ml under static condition and was primarily identified by partial 16s rRNA gene sequence as Bacillus licheniformis ALW1. Optimization studies for the fermentation conditions increased the keratinase biosynthesis to 72.2 U/ml (2.9-fold). The crude extracellular keratinase was optimally active at pH 8.0 and temperature 65 °C with 0.7% soluble keratin as substrate. The produced B. licheniformis ALW1 keratinase exhibited a good stability over pH range from 7 to 9 and over a temperature range 50-60 °C for almost 90 min. The crude enzyme solution was able to degrade native feather up to 63% in redox free system.

Keywords: Bacillus licheniformisALW1; Enzymatic feather degradation; Feather waste; Keratinase; Optimization.

Fig. 1

The growth of most potent bacterial isolate on TSA (A), Transmission electron microscopy examination of the most effective bacterial isolate (B), Molecular phylogenetic analysis based on 16S rDNA partial sequence, showing the relation between isolate Bacillus licheniformis ALW1 and other species of Bacilli, The tree was constructed using MEGA6 programme by Maximum Likelihood method (C).

Fig. 2

The effect of different keratinous substances on keratinase production by B. licheniformis ALW1 (A), The effect of different concentration of feather (%) on keratinase production (B).

Fig. 3

The effect of different incubation temperature on keratinase production by B. licheniformis ALW1.

Fig. 4

The effect of different CSL concentration on keratinase production by B. licheniformis ALW1.

Fig. 5

The effect of inoculums size on keratinase production by B. licheniformis ALW1.

Fig. 6

The effect of different initial pH on keratinase production by B. licheniformis ALW1.

Fig. 7

The ability of B. licheniformis ALW1 to hydrolyze feather in the optimized medium. A: represent feather after autoclaving; B: represent the hydrolysis of feather at the end of fermentation period.

Fig. 8

The effect of reaction temperature and pH on the activity of crude B. licheniformis ALW1 keratinase.

Fig. 9

Thermal stability of the crude B. licheniformis ALW1 keratinase.

Fig. 10

pH stability of the crude B. licheniformis ALW1 keratinase.

Fig. 11

Feather keratin completely hydrolyzed by crude keratinase (A), Dried feather meal (B).