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

[beta]-Glucosidase is an essential part of cellulase enzyme system for efficient and complete hydrolysis of biomass. Psychrotolerant Pseudomonas lutea BG8 produced [beta]-glucosidase with lower temperature optima and hence can play important role in bringing down the energy requirement for bioethanol production. To enhance [beta]-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 [beta]-glucosidase under submerged fermentation. The optimal medium composition for maximum [beta]-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, [beta]-glucosidase production increased up to 9.12-fold (17.52 ± 0.24 IU/g) in shake flask. Large-scale production in 7-L stirred tank bioreactor resulted in higher [beta]-glucosidase production (23.29 ± 0.23 IU/g) within 80 H of incubation, which was 1.34-fold higher than shake flask studies. Commercial cellulase (Celluclast 1.5L) when supplemented with this crude [beta]-glucosidase resulted in improved sugar release (548.4 ± 2.76 mg/gds) from paddy straw at comparatively low temperature (40 °C) of saccharification. P. lutea BG8 therefore showed great potential for cold active [beta]-glucosidase production and can be used as accessory enzyme along with commercial cellulase to improve saccharification efficiency.