Two-step statistical optimization for cold active β-glucosidase production from Pseudomonas lutea BG8 and its application for improving saccharification of paddy straw.

Abstract

β-Glucosidase is an essential part of cellulase enzyme system for efficient and complete hydrolysis of biomass. Psychrotolerant Pseudomonas lutea BG8 produced β-glucosidase with lower temperature optima and hence can play important role in bringing down the energy requirement for bioethanol production. To enhance β-glucosidase production, two statistical tools: Taguchi and Box-Behnken designs were applied to reveal the most influential factors and their respective concentration for maximum production of β-glucosidase under submerged fermentation. The optimal medium composition for maximum β-glucosidase production were 2.99% (w/v) bagasse, 0.33% (w/v) yeast extract, 0.38% (w/v) Triton X-100, 0.39% (w/v) NaNO3 , and pH 8.0 at temperature 30°C. Under optimized conditions, β-glucosidase production increased up to 9.12-fold (17.52±0.24IU/g) in shake flask. Large-scale production in 7-L stirred tank bioreactor resulted in higher β-glucosidase production (23.29±0.23IU/g) within 80H of incubation, which was 1.34-fold higher than shake flask studies. Commercial cellulase (Celluclast® 1.5L) when supplemented with this crude β-glucosidase resulted in improved sugar release (548.4±2.76mg/gds) from paddy straw at comparatively low temperature (40°C) of saccharification. P. lutea BG8 therefore showed great potential for cold active β-glucosidase production and can be used as accessory enzyme along with commercial cellulase to improve saccharification efficiency.