Controlled depolymerization and decrystallization of cellulose-rich substrates into glucose
Date de publication2005
The energy needs are increasing rapidly throughout the world. To fulfill this need, new environmentally friendly energy sources must be developed. Production of bio-ethanol from lignocellulosics, a renewable resource, has a favorable life cycle compared to actual fossil fuels or to bio-ethanol from starch.The main difficulty is to obtain the sugars from the rigid cellulose matrix characteristic of lignocellulosics.The sugars would then be fermented into ethanol. Scientists generally follow two approaches to develop the sugar production process from lignocellulosics, (1) acid hydrolysis and (2) enzymatic hydrolysis. Both approaches produce high glucose recoveries; however, both processes have been, so far, economically unattractive and rely, as the corn-linked process, on subsidies. This project attempts to develop improved methods that make the sugar production from lignocellulosics economically attractive.The acid hydrolysis process is based on the ASTM E1758-95 method, referred to as"Determination of carbohydrates in biomass by HPLC". Our innovation has been to modify the"swelling" and hydrolysis steps inherent in the ASTM method, by using a mediator to produce a more concentrated solution of sugars.The experiment presented in this thesis proves that that proposed innovation is technically feasible. However, the economical feasibility of our innovation hinges upon the recovery and recycling of the acid and mediator.The enzymatic hydrolysis innovation is based on using the substrates produced by steam treatment and evaluating whether or not their enzymatic hydrolysis is preferred (less enzymes and less time) over processes with pre-treated but non-fractionated substrates or in relation to high-purity cellulose as the ultimate standard. Our research shows that time and enzymatic loading are the main factors controlling the hydrolysis. When compared with these two factors, the type of substrate has little effect on enzymatic hydrolysis. From this information, it can be deduced that crystallinity is the key limiting step and barrier to enzymatic activity.
- Génie – Mémoires