A Novel Transformational Process Replacing Dilute Acid Pretreatment with Deacetylation and Mechanical (Disc) Refining for the Conversion of Renewable Biomass to Lower Cost Sugars

The deconstruction of renewable biomass feedstocks into soluble at low cost is a critical component of the biochemical conversion of biomass to fuels and chemicals. Providing low cost high concentration sugar syrups with low levels of chemicals, toxic inhibitors and contaminants, at high process yields is essential for biochemical platform processes.  In this work, we utilize a new, possibly transformational process consisting of deacetylation followed by disc refining (DDR) for the conversion of renewable biomass to low cost sugars at high yields and at high concentrations without a conventional chemical pretreatment step. The new process features a low temperature (80°C) dilute alkaline (40kg NaOH /ODMT corn stover) deacetylation step followed by disc refining under modest energy consumptions. The proposed process was demonstrated using a commercial scale Andritz double disc refiner. Deacetylated corn stover  is refined at varied specific energy ranged from 128kWh to 468kWh per oven dried tonne of corn stover, resulting in monomeric glucose and xylose yield of 82 to 90% and 75~82%, respectively, after enzymatic hydrolysis at process-relevant solids (15 and 20wt% total solids) and enzyme loadings (22.5mg enzyme protein per gram of cellulose). High process sugar conversions were achieved, yielding high concentrations of monomeric sugars that approaching 150g/L, (total (monomeric + oligomeric) sugars >170g/L). Produced sugar syrups also possessed low concentrations of known fermentation inhibitors; furfural and HMF levels were non-detectable and acetic acid was below 0.3g/L. Together, these results indicate that this process is an extremely promising development for the nascent cellulosic biofuels industry.