Organosolv pretreatment produces an inhibitor free hydrolysate with superior fermentability at high-solids loadings

Other conference contribution, 2017

Never has the issue of sustainability garnered so much importance than now. The fifth assessment report by the Intergovernmental Panel on Climate Change necessitates us to take drastic actions to combat the emissions of greenhouse gases. A rising population, an urban lifestyle and increased economic growth would place enormous pressure on the global energy demand and food production. Thus, targeting industrial chemicals – valued at 3 trillion USD per year, with bio-based processes will enable the production of these chemicals from a non-petrochemical feedstock. Towards fulfilling some of the sustainable development goals formulated by the United Nations Biomass is a renewable feedstock that is available abundantly. However, it needs to be processed, to release the sugars that can be utilised by microorganisms to produce various products of interest. Several pretreatment methods are currently available for biomass deconstruction, but inevitably they produce compounds, such as hydroxy methyl furfural and furfural, that are toxic to the microorganisms. Organosolv (with ethanol as a solvent) pretreatment has shown much promise, as it yields three distinct and clean streams — cellulose, hemicellulose and lignin, that are less toxic to the microorganisms. The enriched cellulose fraction can be hydrolysed using a cocktail of enzymes to release the glucose monomers and subsequently be fermented to ethanol using native yeasts. In this study, we report the sugar yields during the hydrolysis of organosolv pretreated birch and spruce biomass and the superior fermentability of birch biomass over spruce, in an SSF process using Ethanol Red yeast. Ethanol yields up to 95% of theoretical maximum at 5% solids loading could be achieved in a small-scale set-up. Studies at a large-scale including LCA analysis would provide conclusive evidence on the efficacy of this pretreatment method over others.