Before the cost of enzyme is down to an economical level, it may be not enough to increase the efficiency and rate of enzymatic hydrolysis of biomass just via a pretreatment.
Because of the nature of hemicelluloses (branched, amorphous, and variety), the severity of pretreatment should be low to avoid hemicelluloses degradation. However the mild pretreatment will not damage cell wall enough and remove part of recalcitrant lignin (the physical barrier and competitive sites for enzyme adsorption). As a result, the efficiency and rate of enzymatic hydrolysis cannot reach the level of what we expect. Ideally, the process should be integrated with several units: pretreatment without washing to pull out hemicelluloses; followed by delignification to remove lignin; enzymatic hydrolysis of delignified biomass with very limited dosage of enzyme to achieve target and high sugar recovery yield. The additional unit may increase capital cost. Considering the saving of enzyme dosage and time, the overall operation and material cost may be lower. If increasing the rate of hydrolysis, the size of equipment can be smaller. Therefore, the integration of process may lead to a overall efficiency.
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