“…The respective protein contents of CTec3 and HTec3 were determined to be 326 mg protein/ml and 243 mg protein/ml using Pierce™ BCA protein assay. 21,35,36 CTec3 is effective for the hydrolysis of cellulose whereas hemicellulase (HTec3) is effective for the hydrolysis of hemicellulose.…”
Section: Enzymesmentioning
confidence: 99%
“…Simultaneous conversion of cellulose and hemicellulose improves xylose and glucose yields; the combined effect increases the hydrolysis rate by disentangling lignocellulose biomass. 35 For both HTec3 and CTec3, the individual enzyme loadings were 2 mg protein/g dry biomass loaded into the enzymatic hydrolysis reactor. This low enzyme loading was chosen to amplify the pretreatment effects.…”
This study investigates digestibility enhancements of lignocellulose from shock pretreatment, alkaline pretreatment, and combination. Shock pretreatment subjects aqueous slurries of lignocellulose to shock waves, which disrupts its structure rendering it more susceptible to hydrolysis. Alkaline pretreatment submerges the biomass in aqueous alkali (NaOH, Ca(OH) 2 ), which removes lignin and acetyl groups. As indicators of digestibility, cellulase (CTec3) and hemicellulase (HTec3) were used to saccharify the pretreated corn stover and the resulting filtrate which contains about 10% of the sugars. Shock is most effective when it precedes alkaline pretreatment, presumably because it opens the biomass structure and enhances diffusion of pretreatment chemicals. Lignocellulose digestibility from calcium hydroxide treatment improves significantly with oxygen addition. In contrast, sodium hydroxide is a more potent alkali, and thereby eliminates the need for oxygen to enhance pretreatment.At low hydroxide loadings (<4 g OH À /100 g dry biomass), both NaOH and Ca(OH) 2 provide similar increases in digestibility; however, at high hydroxide loadings, NaOH is superior. For animal feed, Ca(OH) 2 treatment is recommended, because residual calcium ions are valuable nutrients. In contrast, for methane-arrested anaerobic digestion, NaOH treatment is preferred because NaHCO 3 is a stronger buffer. At 50 C, shock pretreatment improves sugar yields at all NaOH loadings. The effect of shock is most pronounced when the no-shock control employed the same soakingand-drying procedure as the shock treatment. The recommended conditions are shock treatment (5.52 bar [abs] initial H 2 /O 2 pressure) followed by 50 C alkaline treatment with NaOH loading of 4 g OH À /100 g dry biomass for 1 h.
“…The respective protein contents of CTec3 and HTec3 were determined to be 326 mg protein/ml and 243 mg protein/ml using Pierce™ BCA protein assay. 21,35,36 CTec3 is effective for the hydrolysis of cellulose whereas hemicellulase (HTec3) is effective for the hydrolysis of hemicellulose.…”
Section: Enzymesmentioning
confidence: 99%
“…Simultaneous conversion of cellulose and hemicellulose improves xylose and glucose yields; the combined effect increases the hydrolysis rate by disentangling lignocellulose biomass. 35 For both HTec3 and CTec3, the individual enzyme loadings were 2 mg protein/g dry biomass loaded into the enzymatic hydrolysis reactor. This low enzyme loading was chosen to amplify the pretreatment effects.…”
This study investigates digestibility enhancements of lignocellulose from shock pretreatment, alkaline pretreatment, and combination. Shock pretreatment subjects aqueous slurries of lignocellulose to shock waves, which disrupts its structure rendering it more susceptible to hydrolysis. Alkaline pretreatment submerges the biomass in aqueous alkali (NaOH, Ca(OH) 2 ), which removes lignin and acetyl groups. As indicators of digestibility, cellulase (CTec3) and hemicellulase (HTec3) were used to saccharify the pretreated corn stover and the resulting filtrate which contains about 10% of the sugars. Shock is most effective when it precedes alkaline pretreatment, presumably because it opens the biomass structure and enhances diffusion of pretreatment chemicals. Lignocellulose digestibility from calcium hydroxide treatment improves significantly with oxygen addition. In contrast, sodium hydroxide is a more potent alkali, and thereby eliminates the need for oxygen to enhance pretreatment.At low hydroxide loadings (<4 g OH À /100 g dry biomass), both NaOH and Ca(OH) 2 provide similar increases in digestibility; however, at high hydroxide loadings, NaOH is superior. For animal feed, Ca(OH) 2 treatment is recommended, because residual calcium ions are valuable nutrients. In contrast, for methane-arrested anaerobic digestion, NaOH treatment is preferred because NaHCO 3 is a stronger buffer. At 50 C, shock pretreatment improves sugar yields at all NaOH loadings. The effect of shock is most pronounced when the no-shock control employed the same soakingand-drying procedure as the shock treatment. The recommended conditions are shock treatment (5.52 bar [abs] initial H 2 /O 2 pressure) followed by 50 C alkaline treatment with NaOH loading of 4 g OH À /100 g dry biomass for 1 h.
“…Examples include counter-current pretreatment by dilute acid (Lee et al, 1999) or liquid hot water (Thomsen et al, 2006) that have the benefits of minimizing soluble xylan exposure to high temperature and acid, reducing sugar degradation. Counter-current enzymatic hydrolysis of pretreated biomass has also been demonstrated as a concept to minimize product inhibition by high concentrations of sugars (Lonkar et al, 2017). Counter-current sucrose extraction from sugarcane is performed to maximize both sucrose concentrations and extraction efficiency by minimizing the soluble sugars remaining in the extracted bagasse.…”
Sorghum (Sorghum bicolor L. Moench) offers substantial potential as a feedstock for the production of sugar-derived biofuels and biochemical products from cell wall polysaccharides (i. e., cellulose and hemicelluloses) and water-extractable sugars (i.e., glucose, fructose, sucrose, and starch). A number of preprocessing schemes can be envisioned that involve processes such as sugar extraction, pretreatment, and densification that could be employed in decentralized, regional-scale biomass processing depots. In this work, an energy sorghum exhibiting a combination of high biomass productivity and high sugar accumulation was evaluated for its potential for integration into several potential biomass preprocessing schemes. This included counter-current extraction of water-soluble sugars followed by mild NaOH or liquid hot water pretreatment of the extracted bagasse. A novel processing scheme was investigated that could integrate with current diffuser-type extraction systems for sugar extraction. In this approach, mild NaOH pretreatment (i.e., <90 • C) was performed as a counter-current extraction to yield both an extracted, pretreated bagasse and a high-concentration mixed sugar stream. Following hydrolysis of the bagasse, the combined hydrolysates derived from cellulosic sugars and extractable sugars were demonstrated to be fermentable to high ethanol titers (>8%) at high metabolic yields without detoxification using a Saccharomyces cerevisiae strain metabolically engineered and evolved to ferment xylose.
“…Compositional analysis showed that the substrate contained glucan 78.5% and xylan 14.4% [8]. The enzyme used for all experiments was Novozymes Ctec2 (lot # VCPI 0007), a blend of aggressive cellulases with high levels of β-glucosidases and hemicellulases [8, 9]. The protein concentration of the enzyme solution was determined to be 294 mg protein/mL with Pierce BCA assay [8].…”
Section: Methodsmentioning
confidence: 99%
“…The great reduction resulted from the inherent benefits of countercurrent saccharification as well as a longer residence time. Lonkar et al [9] and Liang et al [10] continued this study with pretreated biomass. To achieve the same glucan conversion, as compared to batch, countercurrent saccharification reduced enzyme loadings up to 1.6 and 1.9 times with lime-pretreated and lime + shock-treated corn stover, respectively.Fig.…”
Background
Countercurrent saccharification is a promising way to minimize enzyme loading while obtaining high conversions and product concentrations. However, in countercurrent saccharification experiments, 3–4 months are usually required to acquire a single steady-state data point. To save labor and time, simulation of this process is necessary to test various reaction conditions and determine the optimal operating point. Previously, a suitable kinetic model for countercurrent saccharification has never been reported. The Continuum Particle Distribution Modeling (CPDM) satisfactorily predicts countercurrent fermentation using mixed microbial cultures that digest various feedstocks. Here, CPDM is applied to countercurrent enzymatic saccharification of lignocellulose.
Results
CPDM was used to simulate multi-stage countercurrent saccharifications of a lignocellulose model compound (α-cellulose). The modified HCH-1 model, which accurately predicts long-term batch saccharification, was used as the governing equation in the CPDM model. When validated against experimental countercurrent saccharification data, it predicts experimental glucose concentrations and conversions with the average errors of 3.5% and 4.7%, respectively. CPDM predicts conversion and product concentration with varying enzyme-addition location, total stage number, enzyme loading, liquid residence time (LRT), and solids loading rate (SLR). In addition, countercurrent saccharification was compared to batch saccharification at the same conversion, product concentration, and reactor volume. Results show that countercurrent saccharification is particularly beneficial when the product concentration is low.
Conclusions
The CPDM model was used to simulate multi-stage countercurrent saccharification of α-cellulose. The model predictions agreed well with the experimental glucose concentrations and conversions. CPDM prediction results showed that the enzyme-addition location, enzyme loading, LRT, and SLR significantly affected the glucose concentration and conversion. Compared to batch saccharification at the same conversion, product concentration, and reactor volume, countercurrent saccharification is particularly beneficial when the product concentration is low.
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