Key determinants affecting sheep wool biodegradation directed by a keratinase-producing Bacillus subtilis recombinant strain

Abstract

OVAT (one variable at a time) approach was applied in this study to screen the most important physicochemical key determinants involved in the process of sheep wool biodegradation. The process was directed by a keratinase-producing Bacillus subtilis DB 100 (p5.2) recombinant strain. Data indicate that, sheep wool could be degraded efficiently in cultures incubated at 30°C, with initial pH of 7 with agitation at 150 rpm. Two times autoclaved alkali treated and undefatted chopped sheep wool is more accessible to biodegradation. B. subtilis recombinant cells could utilize sheep wool as a sole source of carbon and nitrogen. Sheep wool-based modified basal medium II, lacking NH₄Cl and yeast extract, could greatly support the growth of these bacterial cells. Sheep wool biodegradation was conducted efficiently in the absence of kanamycin consequently; high stability of the recombinant plasmid (p5.2) represents a great challenge upon scaling up this process. Three key determinants (sheep wool concentration, incubation time and inoculum size) imposing considerable constraints on the process are highlighted. Sheep wool-based tap water medium and sheep wool-based distilled water medium were formulated in this study. High levels of released end products, produced from sheep wool biodegradation are achieved upon using these two sheep wool-based water media. Data indicate that, sheep wool hydrolysate is rich in some amino acids, such as tyrosine, phenylalanine, lysine, proline, isoleucine, leucine, valine, aspartic acid and glutamic acid. Moreover, the resulting sheep wool hydrolysate contains soluble proteins of high and intermediate molecular weights. The present study demonstrates a feasible, cheap, reproducible, efficient and rapid biotechnological approach towards utilization of raw sheep wool waste through a recombinant bacterium.

Characterization and overexpression of a novel keratinase from Bacillus polyfermenticus B4 in recombinant Bacillus subtilis

“…Various bacterial expression systems were utilized for keratinase production, and B. subtilis was a better and more efficient host for keratinase production (Haddar et al 2009;Lin et al 1997;Liu et al 2014;Zaghloul et al 2011). All of them used the expression vectors to heterologously produce keratinase in B. subtilis.…”

Thermal and sound insulation materials from waste wool and recycled polyester fibers and their biodegradation studies

“…It uses less energy in fiber manufacturing than the conventional virgin polyester fibers and also helps in reducing carbon foot print by recycling the plastic bottles which otherwise goes into the landfill sites and remain there for ages as they are not biodegradable. There are some papers available in the literature covering the biodegradation of wool as well as polyester [12,13] fiber based materials. There is no published information available in using the waste wool fibers as raw materials in developing value based dual insulator (thermal and sound insulation) materials.…”

Wool-waste valorization: production of protein hydrolysate with high antioxidative potential by fermentation with a new keratinolytic bacterium,Bacillus pumilusA1

“…Conversely, present data were in disagreement with previous reports stating that optimal temperature for keratin solubilization by Vibrio sp. Kr2 (Grazziotin et al 2007) and B. subtilis recombinant cells (Zaghloul et al 2011) was 30°C.…”