Abstract
BackgroundThe leather industry generates huge volume of waste each year. Keratin is the principal constituents of this waste that is resistant to degradation. Some bacteria have the ability to degrade keratin through synthesis of a protease called keratinase that can be used as sources of animal feed and industrial production of biodiesel, biofertilizer, and bioplastic. Majority of the studies focused on keratin degradation using gram-positive bacteria. Not much of studies are currently available on production of keratinase from gram-negative bacteria and selection of best parameters for the maximum production of enzyme. The aim of this study was to isolate and characterize both groups of bacteria from soil for keratinase and optimize the production parameters. ResultsA total of 50 isolates were used for initial screening of enzyme production in skim milk, casein, and feather meal agar. Out of 50, five isolates showed significantly higher enzyme production in preliminary screening assays. Morphological and biochemical characterization revealed 60% of the isolates as gram-negative bacteria including two highest enzyme-producing isolates. The isolates were identified as Pseudomonas aeruginosa through sequencing of 16S rRNA gene. Maximum production of enzyme from P. aeruginosa YK17 was achieved with 2% chicken feather, beef extract, and ammonium nitrate as organic and inorganic nitrogen sources and glucose as a carbon source. Further analysis revealed that 3% inoculum, 40 °C growth temperature and 72-h incubation, resulted in maximum production of keratinase. ConclusionThe overall results showed significant higher production of enzyme by the P. aeruginosa YK17 that can be used for the degradation of recalcitrant keratin waste and chemical dehairing in leather industries, thereby preventing environmental pollution.
Highlights
The leather industry generates huge volume of waste each year
Out of 50, 16 were identified as keratinolytic bacteria based on the zone of clearance on skim milk (Fig. 1a), casein agar (Fig. 1b), and feather meal agar (Fig. 1c)
Majority of keratinases are belonging to serine proteases, a metalloprotease mostly synthesized by gram-negative bacteria [18]
Summary
The leather industry generates huge volume of waste each year. Keratin is the principal constituents of this waste that is resistant to degradation. Some bacteria have the ability to degrade keratin through synthesis of a protease called keratinase that can be used as sources of animal feed and industrial production of biodiesel, biofertilizer, and bioplastic. 60,000 t of skins and raw hides are processed in the leather industry by dehairing chemicals resulting in release. A diverse type of wastes is produced in leather and poultry industry during the process of hides and skins. This waste contain over 90% of keratin that is highly inert, water insoluble, and non-biodegradable by most proteolytic enzymes such as trypsin, pepsin, and papain [7, 8]. Keratinolytic proteases mostly belong to serine and metalloprotease with broad substrate specificity that have the ability to hydrolyze both soluble (casein, gelatin, albumin) and insoluble (feather, silk, wool) proteins [16]
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