Enzymatic Hydrolysis Strategies for Cellulosic Sugars Production to Obtain Bioethanol from Eucalyptus globulus Bark

Abstract

Cellulosic sugars production for the valorization of lignocellulosic biomass residues in an industrial site has economic benefits and is promising if integrated into a biorefinery. Enzymatic hydrolysis (EH) of pretreated Eucalyptus globulus bark, an industrial residue of low-economic value widely available in Portuguese pulp and paper mills, could be an excellent approach to attain resource circularity and pulp mill profitability. This work evaluated the potential for improving cellulosic sugars concentrations by operating with high solids loading and introducing the additives Triton X-100, PEG 4000 and Tween 80 using a commercial enzymatic consortium with a dosage of 25 FPU gcarbohydrates−1. Additives did not improve enzymatic hydrolysis performance, but the effect of increasing solids loading to 14% (w/v) in batch operation was accomplished. The fed-batch operation strategy was investigated and, when starting with 11% (w/v) solids loading, allowed the feeding of 3% (w/v) fresh feedstock sequentially at 2, 4 and 6 h, attaining 20% (w/v) total solids loading. After 24 h of operation, the concentration of cellulosic sugars reached 161 g L−1, corresponding to an EH conversion efficiency of 76%. Finally, the fermentability of the fed-batch hydrolysate using the Ethanol Red® strain was evaluated in a 5 L bioreactor scale. The present results demonstrate that Eucalyptus globulus bark, previously pretreated by kraft pulping, is a promising feedstock for cellulosic sugars production, allowing it to become the raw material for feeding a wide range of bioprocesses.

Municipal green waste as substrate for the microbial production of platform chemicals

“…However, a higher solid loading also increases the liquefaction time and requires more energy and possibly other equipment. Amândino et al determined a solid loading of 11% ( w / v ) for the enzymatic hydrolysis of Eucalyptus globulus bark as an optimal trade-off between a higher sugar concentration and the hydrolysis conversion efficiency (Amândio et al 2023 ). An optimization of the hydrolysis procedure is necessary to render the process more cost effective.…”

Renewable Carbohydrates: Advancements in Sustainable Glucose Production and Optimization

“…This process plays a crucial role in the production of glucose from biomass, such as cellulose and starch, as it enables the efficient release of glucose units for various industrial applications. The choice of enzymes for enzymatic hydrolysis depends on the type of polysaccharide being targeted (Amandio et al, 2023). Cellulose, for example, requires cellulases, which are enzymes capable of breaking down the β-1,4-glycosidic bonds present in the cellulose chain (ILO, 2020).…”

“…The selection of the appropriate enzyme(s) depends on factors such as substrate specificity, enzyme stability, cost, and availability (Bhandari et al, 2021). The structure and composition of the polysaccharide substrate significantly influence the efficiency of enzymatic hydrolysis (Amandio et al, 2023). Factors such as the degree of polymerization, crystallinity, accessibility of the enzyme to the substrate, and the presence of inhibitors or lignin can affect the hydrolysis process.…”

Monitoring Yeast Cultures Grown on Corn Stover Hydrolysate for Lipid Production

“…More than half of the total dry weight of the lignocellulosic biomass is composed of carbohydrates, which can be used as a carbon source for heterotrophic microbial lipid production. The conversion of cellulose and hemicellulose into fermentable monosaccharides (glucose and mainly xylose, respectively) might be accomplished by hydrolysis, but this should be preceded by a pretreatment step [10]. Pretreatment aims to decrease biomass recalcitrancy by reducing the cellulose crystallinity and increasing the porosity of the material to allow the entry of enzymes [11].…”