A Potent Multi-Cellulase Conjugate System Using a DNA Scaffold to Enhance Cellulose Degradation

Cellulosic biomass consisting of plant matter is the most abundant carbon-neutral renewable resource for the production of bioenergy and biomaterials. Research into the use of biorefineries, which convert cellulosic biomass to valuable fuels and products, has attracted much attention. To enhance degradation of plant cell wall cellulose, several anaerobic microorganisms produce a multi-cellulase complex called a cellulosome. In this study, to mimic a natural cellulosome, we have designed a novel artificial cellulosome as a form of multi-cellulase conjugate assembled onto double-stranded DNA. We anticipated the preparation of this new conjugate in a controllable manner because the length and the amount of the cross-linking site on a DNA scaffold can be tuned by enzymatic protein modification techniques. We chose endoglucanase (EG) as the conjugated cellulase and multiple EGs were site-specifically labeled on DNA scaffolds using a protein cross-linking enzyme, microbial transglutaminase. The catalytic performance of the resultant DNA-(EG)_n conjugates was evaluated by using a crystalline cellulosic substrate (Avicel). We found that the multi-EG aligning strategy worked to enhance enzymatic saccharification compared to the free EGs without the DNA scaffold. The present results may lead to further development of DNA-based designer cellulosomes.