Statistical optimization of cellulase production from Bacillus sp. YE16 isolated from yak dung of the Sikkim Himalayas for its application in bioethanol production using pretreated sugarcane bagasse.

Cellulolytic bacteria were isolated from yak dung samples collected from different habitats of Sikkim, India. Isolate YE16 from the Yumthang Valley sample showed highest enzyme activity of 7.68 U/mL and was identified as Bacillus sp., which has a sequence similarity of 96.15% with B. velezensis. One factor at a time (OFAT) analysis revealed that an acidic pH of 5 with 37 °C temperature was optimum for maximum enzyme production after 36 hrs of incubation (13.88 U/mL), which was further increased after statistical optimization (34.70 U/mL). Media optimization based on response surface methodology predicted that Carboxymethyl cellulose (CMC) and MgSO 4 at concentrations of 30 g/L and 0.525 g/L, respectively, at pH 5.5 to show CMCase activity of 30.612 U/mL, which was consistent with the observed value of 30.25 U/mL and confirmed the model. The crude enzyme also efficiently hydrolyzed alkaline pretreated sugarcane bagasse, releasing 7.09 g/L of glucose equivalent with an ethanol production of 3.05 g. • Cellulolytic bacteria were isolated from dung samples of various habitats of Sikkim. • The isolate YE16 identified as Bacillus sp. showed highest enzyme activity. • Statistical optimization was performed to get an enzyme activity of 34.70 U/mL. • Crude enzyme was able to hydrolyze SCB releasing 7.09 g/L of glucose equivalent. • 3.05 g of ethanol was produced by S. cerevisiae using the enzyme hydrolysate. [ABSTRACT FROM AUTHOR]