Sugar Yield In Enzymatic Hydrolysis Research Articles

Efficacy and Functional Mechanisms of a Two-Stage Pretreatment Approach Based on Alkali and Ionic Liquid for Bioconversion of Waste Medium-Density Fiberboard.

A novel pretreatment strategy utilizing a combination of NaOH and 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) was proposed to enhance the enzymatic hydrolysis of abandoned Medium-density fiberboard (MDF). The synergistic effect of NaOH and [Bmim]Cl pretreatment significantly improved the glucose yield, reaching 445.8 mg/g within 72 h, which was 5.04 times higher than that of the untreated samples. The working mechanism was elucidated according to chemical composition, as well as FTIR, 13C NMR, XRD, and SEM analyses. The combined effects of NaOH and [Bmim]Cl led to lignin degradation, hemicellulose removal, the destruction and erosion of crystalline regions, pores, and an irregular microscopic morphology. In addition, by comparing the enzymatic hydrolysis sugar yield and elemental nitrogen content of untreated MDF samples, eucalyptus, and hot mill fibers (HMF), it was demonstrated that the presence of adhesives and additives in waste MDF significantly influences its hydrolysis process. The sugar yield of untreated MDF samples (88.5 mg/g) was compared with those subjected to hydrothermal pretreatment (183.2 mg/g), Ionic liquid (IL) pretreatment (406.1 mg/g), and microwave-assisted ionic liquid pretreatment (MWI) (281.3 mg/g). A long water bath pretreatment can reduce the effect of adhesives and additives on the enzymatic hydrolysis of waste MDF. The sugar yield produced by the combined pretreatment proposed in this study and the removal ability of adhesives and additives highlight the great potential of our pretreatment technology in the recycling of waste fiberboard.

Achieving high enzymatic hydrolysis sugar yield of sodium hydroxide-pretreated wheat straw with a low cellulase dosage by adding sulfomethylated tannic acid

Sulfonated lignin can significantly enhance the enzymatic hydrolysis of lignocellulose substrates. Lignin is a type of polyphenol, therefore, sulfonated polyphenol, such as tannic acid, is likely to have similar effects. In order to obtain a low-cost and high-efficiency additive to improve enzymatic hydrolysis, sulfomethylated tannic acids (STAs) with different sulfonation degrees were prepared and their impact on enzymatic saccharification of sodium hydroxide-pretreated wheat straw were investigated. Tannic acid strongly inhibited, while STAs strongly promoted the substrate enzymatic digestibility. While adding 0.04 g/g-substrate STA containing 2.4 mmol/g sulfonate group, the glucose yield increased from 60.6% to 97.9% at a low cellulase dosage (5 FPU/g-glucan). The concentration of protein in enzymatic hydrolysate significantly increased with the added STAs, indicating that cellulase preferentially adsorbed with STAs, thereby reducing the amount of cellulase nonproductively anchored on substrate lignin. This result provides a reliable approach for establishing an efficient lignocellulosic enzyme hydrolysis system.

Optimisation of enzymatic saccharification of wheat straw pre-treated with sodium hydroxide

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. The enzymatic hydrolysis was based on the cellulase from Trichoderma reesi ATCC 26921, the optimum NaOH pre-treatment conditions were an NaOH concentration of 1.0% (w/w), a solid content of 5.0% (w/v) and a pre-treatment time of 60 min. Various parameters that affect the enzymatic hydrolysis of wheat straw, including the solid content, enzyme loading, pH and hydrolysis time, were investigated and optimized through a Box–Behnken design and response surface methodology. The predicted optimum conditions for enzymatic hydrolysis were a solid content of 8.0% (w/v), an enzyme loading of 35 FPU/g substrate, a temperature of 50 °C, a pH of 5.3 and a hydrolysis time of 96 h. The experimental result showed that the maximum reducing sugar yield was 60.73% (53.35% higher than the wheat straw without NaOH pre-treatment), which is in accordance with the predicted conditions.

Ethylene glycol based acid pretreatment of corn stover for cellulose enzymatic hydrolysis.

A highly efficient pretreatment strategy using ethylene glycol with dilute sulfuric acid was developed for the fractionation of lignocellulose. The pretreatment behaviors were related to the composition analysis and structure of the samples analyzed by SEM, XRD, FTIR and 2D HSQC NMR, resulting in 80.3% delignification and 84.7% retention of cellulose under the selected conditions (120 °C, 60 min, and 0.6 wt% H2SO4 (w/w)). The enzymatic hydrolysis sugar yield significantly increased from 24.1 to 70.6% (3 FPU g−1), which displayed immense improvement compared with untreated corn stover (24.1%), nearly 3-fold higher than its untreated counterparts. Besides, the regenerated lignin could be fitted to valorize renewable aromatic chemicals and alkane fuels. The present study shows that the pretreatment is a simple, efficient and promising process for corn stover biorefinery.

Comparison of sodium hydroxide and sodium bicarbonate pretreatment methods for characteristic and enzymatic hydrolysis of sago palm bark

ABSTRACTThe present work utilized a by-product of the starch industry in Malaysia, Sago bark waste (SB), for pretreatment and enzymatic hydrolysis. SB was subjected to two types of alkaline pretreatment to assess their effect on SB characteristic, inhibitor formation, and enzymatic hydrolysis sugar yield. Dilute sodium hydroxide (DSH) and dilute sodium bicarbonate (DSB) were used for SB pretreatment. The pretreatment was carried out in a conventional heating environment (120ºC) for 10 min before the enzymatic hydrolysis step. The results showed that the treated SB by DSB resulted in higher removal of lignin (28%) compared to DSH (25%). The TGA, XRD, and SEM analysis results revealed that both types of pretreatment have slight differences. The crystallinity index (CI) for DSH and DSB was 43.2% and 41.2%, respectively. Meanwhile, HPLC results illustrated that the only inhibitor present in the pretreatment liquor is acetic acid at 0.25 mg/ml for DBS pretreatment and 0.063 mg/ml for DSH pretreatment. 229 ± 12 mg/g of total reducing sugar was found using DSH pretreatment, which is slightly higher than that one was obtained by DSB pretreatment (219 ± 16 mg/g) after enzymatic hydrolysis step. A similar observation was found on glucose and xylose yield. These results make us interfere that the diluted level of sodium bicarbonate can lead to approximately similar results of sodium hydroxide, which offer a cheap route of the pretreatment process.

Pretreatment of Bamboo by Ammonium Sulfite for Efficient Enzymatic Hydrolysis

In order to find out the potential effect of ammonium sulfite pretreatment on bamboo for efficient enzymatic saccharification, various ammonium sulfite loadings were conducted to pretreat bamboo at 180 °C for 1–8 h with the solid–liquid ratio of 1:6, respectively. The results verified that ammonium sulfite pretreatment could effectively disrupt the recalcitrance of bamboo and create highly enzymatic hydrolysis sugar yield for further utilization. The contents of lignin in the substrates decreased significantly (from 22.94% to 1.21%) after pretreated and the higher lignin removal with higher chemical loading and longer reaction time during pretreatment. The cellulose-to-glucose conversion yield of pretreated bamboo substrates could achieve almost 100% within 48 h by enzymes loading of 15 FPU of cellulase and 30 IU of β-glucosidase per gram glucan. Therefore, ammonium sulfite pretreatment is argued to be a potential alternative technology for pretreatment of bamboo.

Pretreatment of corn stalk by low concentration tetrabutylammonium hydroxide aqueous solution at low temperature (20–80 °C)

Corn stalk was pretreated by aqueous tetrabutylammonium hydroxide to enhance enzymatic hydrolysis process. The effects of temperature (20–80 °C), concentration of tetrabutylammonium hydroxide (10–40 wt%), time (5–60 min) and ratio of solid to liquid (1:4–1:8, wt/wt) were investigated to find the optimal operational condition, which was determined as 20 °C, 30 wt%, 20 min and 1:5 respectively. This was a quite mild pretreatment condition resulting in 68.17% enzymatic hydrolysis sugar yield and the removal rate of hemicelluloses and lignin were 23.5% and 31.5% respectively. Besides, the microstructure and crystal structure changes of raw material and pretreated samples were analyzed by scanning electron microscope and X-ray diffraction respectively. Finally, a possible mechanism of pretreatment process was put forward based on the comprehensive analysis.

A Comprehensive Investigation on the Effects of Biomass Particle Size in Cellulosic Biofuel Production

Biofuels derived from cellulosic biomass offer one of the best near- to midterm alternatives to petroleum-based liquid transportation fuels. Biofuel conversion is mainly done through a biochemical pathway in which size reduction, pelleting, pretreatment, enzymatic hydrolysis, and fermentation are main processes. Many studies reveal that biomass particle size dictates the energy consumption in the size reduction. Biomass particle size also influences sugar yield in enzymatic hydrolysis, and biofuel yield in fermentation is approximately proportional to the former enzymatic hydrolysis sugar yield. Most reported studies focus on the effects of biomass particle size on a specific process; as a result, in the current literature, there is no commonly accepted guidance to select the overall optimum particle size in order to minimize the energy consumption and maximize sugar yield. This study presents a comprehensive experimental investigation converting three types of biomass (big bluestem, wheat straw, and corn stover) into fermentable sugars and studies the effects of biomass particle size throughout the multistep bioconversion. Three particle sizes (4 mm, 2 mm, and 1 mm) were produced by knife milling and were pelletized with an ultrasonic pelleting system. Dilute acid method was applied to pretreat biomass before enzymatic hydrolysis. Results suggested 2 mm is the optimum particle size to minimize energy consumption in size reduction and pelleting and to maximize sugar yield among the three particle sizes for big bluestem and wheat straw biomass. Nevertheless, there is no significant difference in sugar yield for corn stover for the three particle sizes.

Enhancing enzymatic hydrolysis of corn cob, corn stover and sorghum stalk by dilute aqueous ammonia combined with ultrasonic pretreatment

Ultrasound-assisted dilute aqueous ammonia pretreatment under mild operating conditions has been investigated for intensification of enzyme hydrolysis for corn cob, corn stover and sorghum stalk. The effect of the pretreatment temperature (40–70°C), time (1–4h) and aqueous ammonia concentration (1.0–4.0wt%) on the enzymatic hydrolysis sugar yield (EH sugar yield) were investigated. After that, a series of comparative experiments were conducted using ultrasonic, aqueous ammonia and ultrasonic combined with aqueous ammonia pretreatments for the three materials respectively. In addition, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) of the samples before and after pretreatment were performed in order to investigate the change of the microscopic structures of the biomass. Finally, the main components of the raw materials and the samples after pretreatment by aqueous ammonia or ultrasound-assisted aqueous ammonia were analyzed by van Soest method, indicating the delignification by the pretreatment. It was found that dilute aqueous ammonia combined with ultrasonic pretreatment can improve the accessibility of cellulose in the biomass and improve the enzymatic hydrolysis sugar yield. The largest EH sugar yield was 80.6%, 66.2% and 56.9% for corn cob, corn stover and sorghum stalk, respectively, after the combined pretreatment.

Reinforced acid-pretreatment of Triarrhena lutarioriparia to accelerate its enzymatic hydrolysis

In this study, physical method reinforced chemical pretreatments of Triarrhena lutarioriparia (TL) were compared to explore the higher reducing sugar yield in subsequent enzymatic hydrolysis. Four different pretreatments, namely hydrothermal pretreatment (HTP), dilute acid pretreatment (HCl-P), ultrasound assisted acid pretreatment (HCl+U) and microwave assisted acid pretreatment (HCl+M) were conducted on TL. The structural features of TL after different pretreatments were investigated by Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transformed infrared (FT-IR) techniques. The fractal-like theory was introduced to study the enzymatic hydrolysis kinetics of TL. Results showed that the reducing sugar yield of HCl-P reached 100.14 mg/g, showing 1.34 times higher than that of the raw. Due to the hemicellulose and lignin removal and lignocellulosic structure destruction, ultrasound and microwave irradiation strengthened the HCl-P, leading to a great enhancement of enzymatic hydrolysis of TL, especially the microwave irradiation. Moreover, the fractal-like theory was confirmed to be satisfactory for studying the enzymatic hydrolysis kinetics of lignocellulosic biomass.

Investigation on characteristics of corn stover and sorghum stalk processed by ultrasonic vibration-assisted pelleting

Cellulosic ethanol produced from cellulosic biomass is an alternative to petroleum-based liquid transportation fuels. The cost-effectiveness of cellulosic ethanol manufacturing has been hindered by several technical barriers. One such barrier is that low density of biomass causes high costs of biomass transportation, handling, and storage. Another barrier is low sugar yield in enzymatic hydrolysis, making enzymatic hydrolysis an expensive and slow step. Ultrasonic vibration-assisted (UV-A) pelleting of cellulosic biomass can increase its density and reduce the costs of biomass transportation and handling. In addition, sugar yield of biomass pellets processed by UV-A pelleting was higher than that of particles (unpelleted biomass) with diluted acid pretreatment. The reason that UV-A pelleting could increase sugar yield of biomass is still unclear. The objective of this study was to investigate reasons that UV-A pelleting combined with diluted acid pretreatment could increase sugar yield of biomass. High sugar yield is preferred to achieve high ethanol yield. Effects of UV-A pelleting on biomass characteristics (such as chemical composition, crystallinity index, thermal properties, and morphological structure) were investigated. The results showed there was no significant difference in chemical composition between pellets and particles. However, crystallinity of biomass increased after UV-A pelleting. In addition, pellets had higher decomposition temperature than particles, indicating that pellets were more thermally stable than particles. Examinations on morphological structure of biomass showed that softened surface regions of biomass were removed and cellulose microfibrils were revealed after UV-A pelleting.

Effects of cutting orientation in poplar wood biomass size reduction on enzymatic hydrolysis sugar yield

The aim of this study was to understand how cutting orientation in poplar wood biomass size reduction affects enzymatic hydrolysis sugar yield of wood particles. A metal cutting (milling) machine was used to produce poplar wood particles from three cutting orientations. Results showed that cutting orientation significantly affected enzymatic hydrolysis sugar yield of wood particles. In this study, size reduction from the optimum cutting orientation produced 50% more sugars than the other two cutting orientations. Particles from the cutting orientation with the highest sugar yield had a large enzyme accessible area (125mg orange dye/g biomass, as evaluated by Simons’ stain procedure) and low crystallinity (50% crystallinity index, as calculated by the Segal method). Furthermore, small particle size did not necessarily lead to improvement in enzymatic digestibility.

Ultrasound enhanced enzymatic hydrolysis of Parthenium hysterophorus: A mechanistic investigation

This study has attempted to establish the mechanism of the ultrasound-induced enhancement of enzymatic hydrolysis of pretreated and delignified biomass of Parthenium hysterophorus. A dual approach of statistical optimization of hydrolysis followed by application of sonication at optimum conditions has been adopted. The kinetics of hydrolysis shows a marked 6× increase with sonication, while net sugar yield shows marginal rise of ∼20%. The statistical experimental design reveals the hydrolysis process to be enzyme limited. Profile of sugar yield in ultrasound-assisted enzymatic hydrolysis has been analyzed using HCH-1 model coupled with Genetic Algorithm optimization. The trends in the kinetic and physiological parameters of HCH-1 model reveal that sonication enhances enzyme/substrate affinity and reaction velocity of hydrolysis. The product inhibition of enzyme in all forms (free, adsorbed, complexed) also reduces with ultrasound. These effects are attributed to intense micro-convection induced by ultrasound and cavitation in the liquid medium.

A green and efficient technology for the degradation of cellulosic materials: Structure changes and enhanced enzymatic hydrolysis of natural cellulose pretreated by synergistic interaction of mechanical activation and metal salt

A new technology for the pretreatment of natural cellulose was developed, which combined mechanical activation (MA) and metal salt treatments in a stirring ball mill. Different valent metal nitrates were used to investigate the changes in degree of polymerization (DP) and crystallinity index (CrI) of cellulose after MA+metal salt (MAMS) pretreatment, and Al(NO3)3 showed better pretreatment effect than NaNO3 and Zn(NO3)2. The destruction of morphological structure of cellulose was mainly resulted from intense ball milling, and the comparative studies on the changes of DP and crystal structure of MA and MA+Al(NO3)3 pretreated cellulose samples showed a synergistic interaction of MA and Al(NO3)3 treatments with more effective changes of structural characteristics of MA+Al(NO3)3 pretreated cellulose and substantial increase of reducing sugar yield in enzymatic hydrolysis of cellulose. In addition, the results indicated that the presence of Al(NO3)3 had significant enhancement for the enzymatic hydrolysis of cellulose.

Effects of ultrasonic vibration-assisted pelleting on chemical composition and sugar yield of corn stover and sorghum stalk

Cellulosic ethanol made from cellulosic biomass is an alternative to petroleum-based transportation fuel. The cost-effectiveness of cellulosic ethanol manufacturing has been hindered by several technical barriers. One such barrier is that low density of biomass causes high costs of biomass transportation, handling, and storage. Another barrier is low sugar yield in enzymatic hydrolysis, making enzymatic hydrolysis an expensive and slow step. Ultrasonic vibration-assisted (UV-A) pelleting of cellulosic biomass can increase its density and reduce the costs of biomass transportation and handling. The effects of UV-A pelleting on sugar yield of cellulosic biomass have not been fully investigated. The objective of this paper is to investigate effects of UV-A pelleting on chemical composition and sugar yield of cellulosic biomass. The effects were investigated with and without dilute acid pretreatment using corn stover and sorghum stalk. It was found that there was no significant difference in chemical composition between pelleted and unpelleted biomass whether they went through dilute acid pretreatment or not. After dilute acid pretreatment, cellulose recovery of pelleted biomass was significantly higher than that of unpelleted biomass. UV-A pelleting could significantly increase the sugar yield in enzymatic hydrolysis for both corn stover and sorghum stalk.

Efficient pretreatment of Vietnamese rice straw by soda and sulfate cooking methods for enzymatic saccharification.

This manuscript presents a study on alkaline pretreatment of Vietnamese rice (Oryza sativa L.) straw that grows in Northern Vietnam for enzymatic saccharification. The NaOH pretreatment (soda cooking) and NaOH/Na2S pretreatment (sulfate cooking) were applied for rice straw pretreatment, which have relatively similar condition with industrial pulping processes but at lower temperature. Pretreated biomass solid was then enzymatic hydrolyzed by commercial enzyme Cellic®CTec2 (Novozymes) with enzyme dosage of 35 FPU/g to achieve reducing sugars. The suitable condition for pretreatment was found at temperature of about 100 °C, pretreatment time of 2 h, and solid/liquid ratio of 1:10 with active alkali dosage of 20 % of dry rice straw. Under this pretreatment condition, sugar yield in enzymatic hydrolysis up to 45.33 and 48.92 % over dry rice straw could be obtained after soda cooking and sulfate cooking pretreatment, respectively. Moreover, the changes of components of rice straw after pretreatment were also studied. The crystallinity of cellulose in pretreated biomass solid was calculated from XRD pattern. And the fibril morphology after treatment was revealed by the microscopic observations performed by scanning electron microscope (SEM).

An irradiation-alkaline pretreatment of kenaf core for improving the sugar yield

Kenaf (Hibiscus cannabinus) has received considerable attention as a renewable resource because of its fast growth and low lignin content. In the present study, a combination pretreatment of kenaf core using electron beam irradiation (EBI) and dilute alkali was investigated to improve the sugar yield in enzymatic hydrolysis. In the first step, EBI of the kenaf core was performed at various doses ranging from 100 to 500 kGy. The electron beam-irradiated kenaf core was then autoclaved with 3% dilute alkali at 120 °C for 5 h. The pretreated kenaf core was finally subjected to enzymatic hydrolysis at 50 °C for 24, 48, and 72 h by Celluclast 1.5 L (70 FPU/mL) and Novozyme-188 (40 CbU/mL). A total sugar yield of 72.4% was obtained with a 63.9% yield of glucose from pretreated kenaf core after 72 h of enzymatic hydrolysis. To further analyze effectiveness of EBI pretreatment, characterizations of kenaf core by a two-step process of EBI-alkaline pretreatment were also investigated.

A consistency mapping for the effects on enzymatic hydrolysis sugar yield using two sugar yield definitions in cellulosic biofuel manufacturing

Two different sugar yield definitions (cellulose-based and biomass-based) were used in reported studies investigating the relationship between biomass particle size and enzymatic hydrolysis sugar yield. It is noticed that these reported relationships are not consistent if sugar yield is defined differently. The literature does not contain any reports on the effects of sugar yield definition on the relationship between biomass particle size and enzymatic hydrolysis sugar yield. This paper presents a consistency mapping to show under what conditions the relationships are consistent (or inconsistent) when these two definitions are used. The application of this mapping is illustrated via an experimental study with poplar wood biomass on the relationship between biomass particle size and enzymatic hydrolysis sugar yield using both sugar yield definitions. The application of this mapping is also illustrated via data reported in the literature. Not limited to particle size, this mapping is applicable to investigations of the relationships between a variety of parameters (biomass type, pretreatment condition, etc.) and enzymatic hydrolysis sugar yield.

Effects of ultrasonic vibration-assisted pelleting of cellulosic biomass on sugar yield for biofuel manufacturing

Ultrasonic vibration-assisted (UV-A) pelleting can increase the bulk density of cellulosic biomass, thus reduce the feedstock transportation cost in cellulosic biofuel manufacturing. UV-A pelleting can also increase the biomass sugar yield in enzymatic hydrolysis. There are two major processes in the sugar conversion of cellulosic biomass: pretreatment and enzymatic hydrolysis. Sugar yield definition used in reported UV-A pelleting studies is enzymatic hydrolysis sugar yield. This definition is based on enzymatic hydrolysis this single process without considering the pretreatment process. In fact, converting cellulosic biomass into fermentable sugar (glucose) is the combined effort of pretreatment and enzymatic hydrolysis. There are no papers in the literature investigating whether UV-A pelleting could increase the total sugar yield when both pretreatment and enzymatic hydrolysis are considered. This paper reports the first study using total sugar yield to investigate the effects UV-A pelleting on biomass sugar yield. Experimental results show that, for all the four types of cellulosic biomass (wheat straw, corn stover, switchgrass, and sorghum stalk) used in this study, total sugar yield of biomass processed with UV-A pelleting was 30 to 43 % higher than that of biomass not processed with UV-A pelleting.

Ultrasonic Vibration-Assisted Pelleting of Wheat Straw: A Designed Experimental Investigation on Pellet Quality and Sugar Yield

Increasing demands and concerns for reliable supply of liquid transportation fuels make it important to find alternative sources to petroleum-based fuels. One such alternative is cellulosic ethanol. However, several technical barriers have hindered large-scale, cost-effective manufacturing of cellulosic ethanol, such as low density of cellulosic feedstocks (causing high transportation and storage costs) and low efficiency of enzymatic hydrolysis (causing longer processing time and low sugar yield). Ultrasonic vibration-assisted (UV-A) pelleting can increase the density of cellulosic materials and sugar yield in enzymatic hydrolysis. At present, effects of process variables in UV-A pelleting on pellet quality (density, durability, and spring-back) and sugar yield have not been adequately investigated. This paper reports an experimental investigation on UV-A pelleting of wheat straw. A 24 factorial design is employed to evaluate effects of process variables (moisture content, sieve size, pelleting pressure, and ultrasonic power) on output variables (pellet density, durability, spring-back, and sugar yield).