Some critical aspects of the enzymatic hydrolysis at high dry‐matter content: a review

Abstract

Enzymatic hydrolysis represents the crucial phase in bioethanol production. Its aim is to convert pretreated lignocellulosic polymers in hexose sugars for fermentation into bioethanol. To be economically advantageous, the enzymatic hydrolysis should operate with a high concentration of dry matter. The drawback of this is the increase in the reaction medium's viscosity and consequently bad mixing within the bioreactor due to the complexity of the lignocellulosic polymers. Another critical aspect of the enzymatic hydrolysis is enzyme deactivation, which is mainly due to two factors: the presence of lignin by‐products, originating from the pretreatment of lignocellulosic biomass, and the accumulation of glucose in the reaction medium by cellulose hydrolysis. This review details these two critical aspects of enzymatic hydrolysis conducted with high dry‐matter content. The most relevant milestones and technological solutions to improve rheological performance and to reduce enzyme deactivation have been investigated. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

Arundo donax Refining to Second Generation Bioethanol and Furfural

“…The challenges of high gravity hydrolysis are the high viscosities that limit the mass transfer and results in poor mixing [13]. Furthermore, high concentrations of products, namely cellobiose and glucose, could have an inhibitory effect on cellulases [38,39], whereas high solids concentrations could enhance the unspecific enzyme adsorption by interaction with lignin or lignin-carbohydrate complex [40,41]. In the simultaneous saccharification and fermentation (SSF), high gravity conditions could generate osmotic stress and increase the inhibition by degradation products in the pretreated biomass.…”

A clean and effective potassium hydroxide pretreatment of corncob residue for the enhancement of enzymatic hydrolysis at high solids loading

“…Therefore, the production and utilization of bioenergy by making better use of lignocelluloses is benecial to the reduction of carbon emission and environment protection. 6 The global corn production was more than 900 million tons according to the report from the United States Department of Agriculture and approximately 40-50 million metric tons of corncobs could be collected. 7 Due to its relatively high xylan content (about 25-30 wt%), corncob can be used as a feedstock for xylose (mainly for the production of xylitol), xylooligosaccharides (used as food and feed additives), and furfural production.…”

Lignocellulosic Ethanol: Technology and Economics

“…However, high DM content causes an increase in viscosity, inadequate mass and heat transfer within the bioreactor, and, consequently, a strong reduction in the conversion of cellulose/hemicellulose to fermentable sugars. This problem could be overcome by adopting various fedbatch strategies or coprocessing substrates with different degrees of porosity [94].…”