Multi-Functional Cellulolytic Enzymes Outperform Processive Fungal Cellulases for Co-Production of Nanocellulose and Biofuels.

Research paper by John M JM Yarbrough, Ruoran R Zhang, Ashutosh A Mittal, Todd T Vander Wall, Yannick J YJ Bomble, Stephen R SR Decker, Michael E ME Himmel, Peter N PN Ciesielski

Indexed on: 08 Mar '17Published on: 08 Mar '17Published in: ACS Nano


Producing fuels, chemicals, and materials from renewable resources to meet societal demands remains an important step in the transition to a sustainable, clean energy economy. The use of cellulolytic enzymes for the production of nanocellulose enables the co-production of sugars for biofuels production in a format that is largely compatible with the process design employed by modern lignocellulosic (second generation) biorefineries. However, yields of enzymatically produced nanocellulose are typically much lower than those achieved by mineral acid production methods. In this study, we compare the capacity for co-production of nanocellulose and fermentable sugars using two vastly different cellulase systems: the classical "free enzyme" system of the saprophytic fungus, Trichoderma reesei (T. reesei) and the complexed, multi-functional enzymes produced by the hot springs resident, Caldicellulosiruptor bescii (C. bescii). We demonstrate by comparative digestions that the C. bescii system outperforms the fungal enzyme system in terms of total cellulose conversion, sugar production, and nanocellulose production. In addition, we show by multi-modal imaging and dynamic light scattering that the nanocellulose produced by the C. bescii cellulase system is substantially more uniform than that produced by the T. reesei system. These disparities in the yields and characteristics of the nanocellulose produced by these contrasting enzyme systems can be attributed to the dramatic differences in the modes of action of the dominant enzymes in each system.