Impact of protein blocking on enzymatic saccharification of bagasse from sugarcane clones

Abstract

Lignin plays an important functional and structural role in plants, but also contributes to the recalcitrance of lignocellulosic biomass to hydrolysis. This study addresses the influence of lignin in hydrolysis of sugarcane bagasse from conventional bred lines (UFV260 and UFV204) that were selected from 432 field-grown clones. In addition to higher sugar production, bagasse clone UFV204 had a small, but statistically significant, lower insoluble lignin content compared with clone UFV260 (15.5% vs, 16.6%) and also exhibited a significantly higher cellulose conversion to glucose (81.3% vs. 63.3%) at a cellulase loading of 5 (filter paper unit) FPU/g of glucan or 3 FPU/g total solids for liquid hot water pretreated bagasse (200°C, 10 min). The enzyme loading was further decreased by 50% to 2.5 FPU/g glucan and resulted in a similar glucan conversion (88.5%) for clone UFV204 when the bagasse was preincubated with bovine serum albumin at pH 4.8 and nonproductive binding of cellulase components was blocked. Comparison of Langmuir adsorption isotherms and differential adsorption of the three major cellulolytic enzyme components endoglucanase, cellobiohydrolase, and β-glucosidase help to explain differences due to lignin content. K E Y W O R D Sadsorption isotherms, bagasse clones, bovine serum albumin, enzymatic hydrolysis, lignin

Effect of Lignin Content on Cellulolytic Saccharification of Liquid Hot Water Pretreated Sugarcane Bagasse

“…The soluble phenolic compounds derived from the higher severity pretreatment decreased cellulolytic activity to a significantly greater degree than the inhibition resulting from pretreatment with a severity factor of 3.83 [28]. The chemical composition data of SCB here differs from our previous work, where it had higher cellulose (49%-51%), hemicellulose (24%-25%), and lower lignin (23%-25%) components in the initial SCB [8]. This likely reflects the normal variation that will occur under differing growth conditions year to year and field to field.…”

“…In this work, we have demonstrated that even relatively small differences in lignin content can result in considerably increased sugar production, which supports the dissimilarity of bagasse lignin content and its effects on cellulose digestibility. The increased glucose yields with the addition of BSA helped to decrease the inhibition of non-productive absorption of cellulose enzymes onto lignin and solid residual lignin fractions.Molecules 2020, 25, 623 2 of 12 biofuel production [4,[6][7][8][9][10]. In particular, the physical barrier of lignin prevents enzyme access to cellulose and hemicellulose.…”

“…In addition, the pretreatment of lignocellulosic biomass to increase access often results in the production of lignin-derived molecules (mainly phenolic acids) that inhibit enzyme activity and/or subsequent downstream processes such as microbial fermentation. The presence of lignin presents another hurdle for efficient enzymatic saccharification of biomass through non-productive binding of the enzymes [8,[11][12][13][14].Pretreatment principally solubilizes hemicellulose and lignin, and reveals inner cellulose molecules that are susceptible to being hydrolyzed by cellulolytic enzymes [15,16]. In addition, substrate particle size, cellulose crystallinity, and cellulose degree of polymerization are decreased during pretreatment, which results increased porosity and surface area that helps digestibility with cellulolytic enzymes [17][18][19][20].…”

“…Molecules 2020, 25, 623 2 of 12 biofuel production [4,[6][7][8][9][10]. In particular, the physical barrier of lignin prevents enzyme access to cellulose and hemicellulose.…”

“…In addition, the pretreatment of lignocellulosic biomass to increase access often results in the production of lignin-derived molecules (mainly phenolic acids) that inhibit enzyme activity and/or subsequent downstream processes such as microbial fermentation. The presence of lignin presents another hurdle for efficient enzymatic saccharification of biomass through non-productive binding of the enzymes [8,[11][12][13][14].…”