Improving the Sustainability of Cellulose Nanocrystal Production through Ethanol Co-generation

Dawit Beyene1, Jing Dai1, Christophe Danumah2, Frank Tosto2, Michael Chae1, David C. Bressler1.
1Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada.
2Alberta Innovates – Technology Futures, 250 Karl Clark Road, Edmonton, Alberta, Canada.

The forestry industry is transforming from low demand paper products to high value chemicals and materials to sustain and improve its revenue. Among the novel materials, cellulose nanocrystals (CNCs) are receiving a lot of attention with potential applications in many industries. CNC is a nanoscale fibre particle derived from crystalline cellulose by acid hydrolysis. These fibers have high tensile strength and elasticity at low density, which are desirable properties for reinforcing composite products in the automotive, paint, pharmaceutical and food packaging industries. In the current industrial acid hydrolysis process, only 20 % of the wood pulp is converted to CNC, while 80 % of the sugar rich bulk biomass enters the acid waste stream that is extremely difficult to process for recovery. In this presentation, we report efforts to introduce a novel enzymatic treatment to breakdown amorphous regions, which makes up 40 % of the cellulose in wood, to recover sugars for ethanol fermentation. The undigested crystalline cellulose (60 %) will then be used as feedstock for acid hydrolysis. This high crystalline loading will improve acid utilization efficiency and reduce toxic waste. The enzymatic degradation profile of Poplar wood Kraft pulp using proprietary cellulases from Novozymes a) endoglucanases b) a cocktail (endoglucanase, exoglucanase and β- glucosidase) and Celluclast 1.5L, a commercial cellulases cocktail were studied at varying enzyme concentrations and reaction periods. Substantial glucose yield was not obtained from the endoglucanases after 72 hr (1.2 – 1.5 %), while the cocktail enzyme and Celluclast 1.5L conferred above 40 % glucose yield in 6 and 72 hrs, respectively. Further treatment of liquid fraction of the endoglucanase hydrolysate will be carried out to break down short chain sugars to improve glucose yield. The cellulose solids recovered from 20 – 40 % pulp degradation will be acid hydrolysed to evaluate cellulose nanocrystals yield.