Abstract: Aim: To obtain an engineered bacterial strain able to express cellulose-degrading enzymes through constructing an integration vector using Bacillus subtilis as the host. Methods: The homologous fragments M1 and M2 were cloned by polymerase chain reaction (PCR) from the genome of B. subtilis LN. The glucosidase gene CelKg, homologous fragments M1 and M2 and the strong promoter P43 were ligated to the pGEM-T vector by T4 DNA Ligase to construct the integrated vector pGEM-Kmpgmt. The vector was then transformed to B. subtilis LN by double crossover homologous recombination method. Results: The integration vector was successfully constructed and integrated into the genome of B. subtilis LN, as verified by PCR. Congo red staining indicated that the recombinant B. subtilis could obviously degrade sodium carboxymethyl cellulose in the medium. The cellulase activity from the culture supernatant harvested after 18 h culture of the recombinant strain in a modified medium at 37 ℃ with shaking was increased by 115% as compared with the wild-type B. subtilis LN.

Key words: homologous recombination, cellulase, Bacillus subtilis