Abstract
Wool keratin is difficult to degrade as comparing to feathers because of its tough secondary structure. In order to develop an approach for high-value utilization of wool fiber waste by keratinolytic microorganisms, which is produced from shearing, weaving, and industrial processing of wool, screening of wool-degrading bacterium with high degradation efficiency were performed in this study. To this end, Lysobacter brunescens YQ20 was identified and characterized. The optimized conditions for wool degradation were pH 9.0 and 37°C with 20% liquid volume of Erlenmeyer flask. After fermentation, 15 essential amino acids were detected when wool fiber waste was fermented. The total amino acids produced from 1% wool per hour were 13.7 mg/L. The concentration was 8.6-fold higher than that produced by the strain Stenotrophomonas maltophilia BBE11-1, which had previously been reported to have the highest wool-degrading capacity. Our study reports the first Lysobacter strain that exhibits efficient wool degradation and yields higher concentrations of amino acids than previously reported strains. Whole-genome sequencing indicated that there were 18 keratinase-like genes in the genome of YQ20, which exhibited a long evolutionary distance from those of Bacillus. Therefore, L. brunescens YQ20 may have applications in the environmentally friendly management of wool waste as fertilizer in agriculture.
Highlights
In the wool processing industry, wool is processed into a series of products, including cashmere and yarn, which are used for the manufacturing of various goods, such as clothing items, carpets, and tapestries
When fermentation was carried out with 1% wool fiber waste as a substrate, there was a significant increase in amino acids produced until 36 h
Previous studies have shown that most keratinases are serine proteases (Gradišar et al, 2005)
Summary
In the wool processing industry, wool is processed into a series of products, including cashmere and yarn, which are used for the manufacturing of various goods, such as clothing items, carpets, and tapestries. An abundance of rough wool fibers are left as wastes (Zoccola et al, 2012). A considerable amount of low-grade wool waste is generated from abattoir processing and farming wool trimming practices. Wool is mainly made up of two major types of protein, i.e., keratin proteins and keratinassociated proteins (Plowman et al, 2012). The major component of wool is keratin protein, accounting for approximately 95% of wool components (Shavandi et al, 2016). According to their secondary structures, keratins can be divided into α-keratin and β-keratin, which consist
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