Isolation of thermophilic <i>Bacillus </i>sp. strain EF_TYK1-5 and production of industrially important thermostable α-amylase using suspended solids for fermentation

Abstract

<i>Bacillus sp. </i>strain EF_TYK1<i>-5 </i>strain was isolated from hot water spring at Unkeshwar (19^o 85’ N and 78^o 25’ E), Nanded district, Maharashtra, India. The optimum activity of α-amylase extracted from the same was observed at 60 °C temperature. The enzyme showed maximum activity with Ca++ and Co++ at 60 °C temperature. The enzyme was stable in the pH range of 4.0-9.0 and 50-90 °C temperatures under SmF. The enzyme showed stability towards surfactant (SDS) at 5 mM concentrations. The thermostable enzyme isolated was compatible and works in the presence of detergents <i>(Surf excel^TM, Ariel^TM, Tide^TM, Ghadi^TM, Wheel^TM and Nirma^TM </i>at 1% concentration). Agricultural wastes as substrate such as rice hull, wheat bran, millet, soyabean husk, and tamarind seeds were studied for enzyme activation under suspension solid fermentation. Of these, rice hull was proved as the

best substrate for a-amylase production (10 U/mg) by organism after 24 h incubation, 1,000 µm particle sizes, and 1% inoculum level (v/w), 55 °C temperatures. Optimum temperature and pH for enzyme production were 60 °C &nbsp;(85.56 U/mg), and 7.0 (46.71 U/mg) respectively. Additional carbon sources, 1% lactose (47.84 U/mg) enhanced α-amylase production. Among the various nitrogen sources tested, 1% beef extract (172.43 U/mg) was observed as the best nitrogen source for α-amylase production. The maximum α-amylase production was observed as 124 U/mg at 24 h, 1,000 m particle size, and 20% inoculum level (v/w), pH 7.0, 1% lactose, 1% beef extract, temperature 65 °C. The values of <i>K_m </i>and <i>V_max </i>were 1.3699 mg/mL and 0.000074 mmol respectively.