Abstract
Background Cellulosic biomass degradation still needed more studies while bioenergy is becoming mainly energy in future and more evaluate bacteria isolation laid a foundation of further study. Qinling Mountains have unique biodiversity, acting as promising source of cellulose-degrading bacteria exhibiting noteworthy properties. The aim of this work was to find potential cellulolytic bacteria in depredating multiform carbon source cellulose substrate. Results In this study, 55 potential cellulolytic bacteria screened out and were identified. Based on the results of the investigation of cellulase activities and reducing sugar content via different carbon substrate effect, Bacillus methylotrophicus 1EJ7, Bacillus subtilis 1AJ3 and Bacillus subtilis 3BJ4 were further taken to hydrolyze wheat straw, corn stover and switchgrass, suggesting that B. methylotrophicus 1EJ7 was the most preponderant bacterium, obtaining highest sugar content (95mg/100mL) in switchgrass, wheat straw and corn stover. Scanning electron microscopy (SEM) and X-ray diffraction results of wheat straw surface and crystallinity indicated the hydrolyzation. By ascertaining the target sequence of cellulase for the cloning and expression in an economical and convenient manner, the genes of β-glucosidase (243 aa) and endoglucanase (499 aa) of B. methylotrophicus 1EJ7. Recombinant β-glucosidase from GH16 family and enzyme activity was 1670.15±18.94 U/mL. Endoglucanase consist of GH5 family catalytic domain and a carbohydrate-binding module belongs to CBM3 family and enzyme activity was 0.130±0.002 U/mL. Conclusions Screened, identified the cellulolytic bacteria from rotten wood of Qinling Mountains and explored their ability in degrading different carbon source cellulose substrate, including purified and natural carbon sources. Bacillus were the predominant species among the isolated strains, and Bacillus methylotrophicus 1EJ7 performant well on cellulose degradation. In the meantime, the β-glucosidase and endoglucanase were successfully cloned and expressed from Bacillus methylotrophicus for the first time. The strain and the recombinant enzyme have potential application in industrial production.
Bacterial Synergism in Lignocellulose Biomass Degradation – Complementary Roles of Degraders As Influenced by Complexity of the Carbon Source
