Abstract
The study was conducted to select the best promising keratinolytic bacterial strain. A good keratinase positive bacterium isolated from the soil samples of Hazaribagh tannery industrial zone, Dhaka was identified as Arthrobacter genus depending on the conventional techniques and confirmed as Arthrobacter sp. by sequencing 16S rRNA gene. The medium components and culture conditions were optimized to enhance keratinase production through shake flask culture. Keratin and feather powder (10 g/l or 1%) were good substrates for the highest keratinase production along with yeast extract (0.2 g/l or 0.02%) as an organic nitrogen source and potassium nitrate (1 g or 0.1%) as an inorganic nitrogen source. Maximum yield of keratinase was found after 24 h of incubation at 37 °C with an initial pH of 7.0 and inoculums volume 5% under 150 rpm when keratin, yeast extract and potassium nitrate were used as nutrient sources. Keratinase production was more than 5.0-fold increased when all optimized parameters were applied simultaneously. The optimum reaction temperature and pH were determined to be 40 °C and 8.0 respectively for crude keratinase activity. Therefore, Arthrobacter sp. NFH5 might be used for large scale production of keratinase for industrial purposes in less time.
Highlights
A huge amount of feather and leather wastes are generated every year as a by-product from the poultry and tannery industry due to continuous meat consumption worldwide
In the present study, bacteria were isolated from collected soil samples and screened for keratinase producing capability on the basis of clear zone formation
The higher clear zone forming isolate on both media was considered as better keratinase producer
Summary
A huge amount of feather and leather wastes are generated every year as a by-product from the poultry and tannery industry due to continuous meat consumption worldwide. Bacterial keratinases have potentiality because of their activity on degradation of specific insoluble keratin substrates and generally on a variety of protein materials (Lin et al 1996) This enzymes work as novel biocatalysts that have many applications in several sectors including in leather, textile and detergents industries, enhancing drug delivery system and medical application, in cosmetics, prion degradations, as pesticides, production of biodegradable films or bioprocessing of used X-ray film, in glues and foils and agro-industrial waste degradation (Saber et al 2010; Mazotto et al 2011a, b; Mohanapriya et al 2014; Mohorcic et al 2007; Gupta et al 2002; Zaghloul et al 2004). Selected keratinase positive bacteria were further confirmed by using feather meal powder in the medium instead of keratin The isolates those produce clear zones on both media were considered as keratinase producers. Neighbor-joining phylogenetic tree was constructed based on the 16S rRNA sequences using MEGA6 (Tamura et al 2013)
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