Optimization of Physico-Chemical Parameters for Hyper Keratinase Production from a Newly Isolated Aspergillus sp. DHE7 using Chicken Feather as Substrate- Management of Biowaste

Abstract

Keratinases have recently gained biotechnological impetus due to their ability in degrading insoluble keratinous solid wastes into simplified forms, which used in the preparation of nitrogenous fertilizers, biodegradable films, glues and foils. Keratinases are widespread in nature and mainly produced by diverse microorganisms including bacteria, fungi and actinomycetes. Therefore, the aim of the present work was to isolate and identify a new potent fungal strain possessing extracellular keratinase production capacity using keratinous solid wastes as the sole carbon and nitrogen sources. Fifteen keratinolytic fungi, isolated from a poultry farm soil using white chicken feathers as substrate, were screened qualitatively and quantitatively for their ability to produce extracellular keratinase. Medium optimization for enzyme production was also studied under submerged fermentation conditions. The results revealed that a new fungus identified as Aspergillus sp. DHE7 was reported as the most potent fungal strain for extracellular keratinase production under submerged shaking conditions (120 rpm). The highest yield of enzyme of 199+4.2 U/mL was observed after four days of incubation at pH 6.0 and temperature 30 °C using 2 % of chicken feathers as substrate. Medium supplementation with 0.5 % sucrose as an additional source of carbon increased keratinase yield to 226+5.4 U/mL. While using additional nitrogen sources could not promote a favorable effect on keratinase productivity as compared with the basal medium. Different keratinous wastes were used as substrate in the basal medium and better keratinase production was obtained with goat hair medium (452+12.3 U/mL) followed by turkey feather (435+9.2 U/mL) and sheep wool (322+13.4 U/mL) media. The present data suggest Aspergillus sp. DHE7 as a potential keratinolytic strain for the bioconversion of keratinous wastes, through a non-polluting process.

Culturable Fungi from Urban Soils in China I: Description of 10 New Taxa

“…Keratinophilic fungi involve a large number of taxa belonging to several orders, families, and genera, including mainly dermatophytes and some saprophytic fungi, such as some species of Arthrodermataceae and Onygenaceae in the order Onygenales ( 10 ) and some members of the genera Geomyces and Pseudogymnoascus in the order Thelebolales ( 11 ). In addition, they contain a large number of common taxa, such as some species of the genera Aspergillus , Penicillium , and Trichoderma ( 12 , 13 ). In the years since we investigated the members of keratin-degrading fungal communities in Chinese soils, several new taxa have been identified and reported ( 14 – 22 ).…”

Optimization of Conditions for Feather Waste Biodegradation by Geophilic Trichophyton ajelloi Fungal Strains towards Further Agricultural Use

“…Optimization of keratinase and protease activity occurs at different temperatures and pH, as well as with different amounts of feather waste. Considering the effect of the concentration of chicken feather waste on the increased release of keratinolytic and proteolytic enzymes, El-Ghonemy and Ali [ 57 ] showed that higher production of keratinase and protease by the Aspergillus sp. strain DHE 7 was favored by increased native feather keratin concentration (2%).…”

“…On the other hand, a further increase in feather concentration to 3, 4, and 5% inhibited keratinase activity, but not the release of soluble proteins and peptides. It is possible, as El-Ghonemy and Ali [ 57 ] assumed, that this effect was related to the activity of fungal proteases. As opposed to keratinases, whose secretion is induced by the presence of a substrate, proteases belong to constitutional enzymes and their secretion is induced by nutritional stress, i.e., the lack of carbon, nitrogen, and energy sources [ 58 ].…”

“…These authors recorded in the cultures of Chrysosporium pannorum and Scopulariopsis brevicaulis more than a 2-fold increase in protein concentration in the variant with glucose. In the study conducted by El-Ghonemy and Ali [ 57 ], the release of proteins during keratinolysis by Aspergillus sp. DHE7 increased with increasing concentration of feather waste, despite a decrease in keratinase activity.…”