Enhancement of Escherichia coli cellulolytic activity by co- production of beta-glucosidase and endoglucanase enzymes

Cellulase is a group of enzymes (endoglucanase, exoglucanase and betaglucosidase) required for cellulosic feedstock hydrolysis during bioethanol production. The use of recombinant cellulase is a strategy to reduce the enzyme cost. In this context, the present work describes the construction of a cellulase expression vector (pEglABglA), which allowed constitutive co-expression of endoglucanase A (EglA) from an endophytic Bacillus pumilus and the hyperthermophilic β-glucosidase A (BglA) from Fervidobacterium sp. in Escherichia coli. When compared to the nonmodified strain DH5α, the recombinant Escherichia coli DH5α (pEglABglA) reduced fivefold the viscosity of the carboxymethylcellulose medium (CMC-M). Also, it presented almost 30-fold increase in reducing sugar released from CMC-M, enabling the recombinant strain to grow using CMC as the sole carbon and energy source. When cultivated in rich media, specific growth rates of recombinant E. coli strains BL21, JM101 and Top10 were higher than those of DH5α and DH10B strains. The constructed plasmid (pEglABglA) can be used as backbone for further cellulase gene addition, which may enhance even more E. coli cellulolytic capacity and growth rate.