Factors affecting cellulose hydrolysis and the potential of enzyme recycle to enhance the efficiency of an integrated wood to ethanol process

Abstract

Past technoeconomic modeling work has identified the relatively large contribution that enzymatic hydrolysis adds to the total cost of producing ethanol from lignocellulosic substrates. This cost was primarily due to the high concentration of enzyme and long incubation time that was required to obtain complete hydrolysis. Although enzyme and substrate concentration and end‐product inhibition influenced the rate of hydrolysis, the effect was less pronounced during the initial stages of hydrolysis. During this time most of the cellulases were adsorbed onto the unhydrolyzed residue. By recycling the cellulases adsorbed to the residual substrate remaining after an initial 24 h, a high rate of hydrolysis, with low overall residence time and minimal cellulase input, could be achieved for several rounds of enzyme recycle. A comparison of the front end (pretreatment, fractionation, and hydrolysis) of a softwood/hardwood to ethanol process indicated that the lignin associated with the softwood‐derived cellulose stream limited the number of times the cellulose containing residue could be recycled. © 1996 John Wiley & Sons, Inc.

Switchgrass for bioethanol and other value-added applications: A review

“…Most fungal cellulases are deficient in β-glucosidase activity, which must be supplemented since cellobiose accumulation results in cellulase inhibition (Ryu and Mandels, 1980). A cellulase dosage of 10 FPU (filter paper units) per gram of biomass is often used in studies as it enables high glucose yields in 48-72 h (Gregg and Saddler, 1996). However, a range of dosage and hydrolysis conditions have been reported depending on composition of the substrates and pretreatment used.…”

An Approach to Identify the Suitable Plant Location for Miscanthus-Based Ethanol Industry: A Case Study in Ontario, Canada

“…The solid content in the Miscanthus slurry is considered to be 10% (wt). Although the enzyme loading is noted to vary from 10 FPU/g-cellu to 20 FPU/g-cellulose in producing ethanol from Miscanthus [33,43], it is assumed to be 8.04 FPU/g Miscanthus. The ethanol yield is also reported to vary from 0.189 L/kg to 0.427 L/kg [39,[44][45][46].…”

Biobutanol Production from Agricultural Waste: A Simple Approach for Pre-Treatment and Hydrolysis

“…However, the sugar concentration started to decrease after three hours. Besides suggestions on enzyme adsorptive loss through inhibition by lignin degradation products [9], microscopic analyses showed increasing microbial activity, which effectively consumed any sugars formed during the hydrolysis. Thus, substrate sterilization was introduced.…”

“…The enzyme concentration for hydrolysis (20 FPU/g) was chosen according to recommendations [9]. Decrease in enzyme concentration below 5 FPU/g with the purpose of cost reduction gave lower sugar formation rates, and was not used further.…”