Enzymatic Hydrolysis Performance Research Articles

Elucidating the impact of dual modification with hydroxypropylation and enzymatic hydrolysis on physicochemical properties of corn and sago starch

Enzymatic hydrolysis is one of the most commonly used techniques in starch modification. However, the performance of enzymatic hydrolysis has been restricted by the inherent properties of native starch. In this study, hydroxypropylation with two different concentration levels of propylene oxide (10% and 20%) was carried out on corn and sago starches. The effect of hydroxypropylation on the physico-chemical properties of the enzyme-hydrolyzed starch was investigated. The results showed that the starches treated with 20% propylene oxide had higher molar substitution and dextrose equivalent with greater effects. Scanning electron microscope (SEM) revealed that hydoxypropylation had developed pores and pits on the granular surfaces and subsequently enhanced enzyme penetration. Hydroxypropylation showed no changes in the crystalline pattern, yet a decrease in the amylose content of both corn and sago starches, respectively. Other than that, hydroxypropylation decreased the pasting properties and retrogradation tendency but increased the swelling power of enzymehydrolyzed starch significantly. Overall, this work suggested that hydoxypropylation pretreatment could improve the efficiency of subsequent enzyme hydrolysis and produce modified starch with great potential in food processing applications.

Study on the effect of phenoxyethanol-citric acid pretreatment for the enzymatic hydrolysis of bamboo residues.

This study investigated the biphasic phenoxyethanol-citric acid (PECA) pretreatment for bamboo residues (BRs) and its corresponding effects on the enzymatic hydrolysis performance. It is found that increasing the concentration of citric acid in the pretreatment system from 2.5% to 15% greatly enhanced the delignification and xylan removal for BRs. Consequently, the enzymatic hydrolysis yield of pretreated BRs significantly enhanced, increasing from 12.4% to 58.2% and 28.0%72.4% when the concentration of citric acid was increased from 2.5% to 15.0% at 160°C and 170°C, respectively. The characterization results from cellulose crystallinity, accessibility, and hydrophobicity of pretreated bamboo residues indicated that their changes possessed a beneficial performance on the enzymatic hydrolysis yield, which could result from the synergistic removal of lignin and xylan. The Chrastil model analysis showed that pretreatment at higher conditions resulted in the pretreated BRs possessing weaker diffusion resistance for cellulase, which is attributed to its higher enzymatic hydrolysis yield.

Enhancing enzymatic conversion of castor stalk through dual-functional ethanolamine pretreatment

Castor stalk from hemp plants is an attractive lignocellulosic feedstock for biomass refining valorization due to its similar chemical composition to hardwoods. In this study, the castor stalk fibers were pretreated with efficient dual-functional ethanolamine to achieve delignification and swelling of the cellulosic fibers, followed by cellulase enzymatic digestion for biomass conversion. Experimental results showed that ethanolamine pretreatment at 160 °C for 1 h effectively removed 69.20 % of lignin and 43.18 % of hemicellulose. In addition to efficient delignification and removal of hemicellulose, the study also revealed that supramolecular structure of cellulose was another major factor affecting enzymatic hydrolysis performance. The lowered crystallinity (60–70 %) and swelled crystal sizes (2.95–3.04 nm) promoted enzymatic hydrolysis efficiency during the heterogeneous reaction process. Under optimal conditions (160 °C, 1 h; enzyme loading: 15 FPU/g substrate), promoted yields of 100 % glucose and over 90 % xylose were achieved, which were significantly higher than those obtained from untreated castor stalk. These findings highlighted the effectiveness of the dual-functional ethanolamine pretreatment strategy for efficient bioconversion of lignocellulosic feedstocks. Overall, this study provides valuable insights into the development of new strategies for the efficient utilization of biomass resources, which is essential for the sustainable development of our society.

Enhancing the valorization efficiency of Camellia oil extraction wastes through sequential green acid pretreatment and solid-state fermentation-based enzymatic hydrolysis

This study focuses on the underutilized Camellia oleifera oil extraction wastes, namely C. oleifera shell (COS) and cake (COC), which are often overlooked due to their high recalcitrance and antimicrobial properties. COS was found to be an ideal substrate for producing on-site enzymes through solid-state fermentation (SSF) that can be used for lignocellulosic biomass degradation. Additionally, pretreating COS with 2 % (w/v) oxalic acid greatly enhanced sugar production, achieving 9.22 and 5.24 times more sugar compared to room temperature and thermal pretreatment methods, respectively. The highest sugar of 28 g/L was achieved by utilizing a mixture of COS and COC. Enzymatic hydrolysis performance was evaluated through three routes. In the first two routes, the whole pretreated slurry was employed, except the pH was adjusted in route 2. In route 3, the pretreated hydrolysate was recovered, while the solid residue underwent further enzymatic hydrolysis. Ultimately, route 3 resulted in the highest sugar of 20.58 g/L, using SSF enzymes and oxalic acid pretreated solid residues of COS and COC mixture. This value is twice the performance achieved using a single substrate of COS. The fine-tuning strategy employed in route 3 led to (1) achieving high sugar recovery from pretreatment and enzymatic hydrolysis, (2) minimizing water and alkaline regulator consumption, and (3) optimizing resource utilization efficiency. The effectiveness of this approach was also attributed to the synergistic effect of oxalic acid pretreatment and the use of mixed substrate. The possible mechanisms underlying these processes were discussed, offering potential directions for future studies aimed at developing even more efficient approaches.

Sustainable wheat straw pretreatment process by self-produced and cyclical crude lactic acid

The purpose of this study was to investigate an environmentally friendly and recyclable pretreatment approach that would enhance the enzymatic digestibility of wheat straw. Wheat straw was pretreated using self-produced crude lactic acid obtained from enzymatic hydrolysate fermentation by Bacillus coagulans. Experimentally, crude lactic acid at low concentration could achieve a pretreatment effect comparable to that of commercial lactic acid. After pretreatment at 180 °C for 60 min with 2.0 % crude lactic acid, hemicellulose could be effectively separated and high recovery of cellulose was ensured, achieving cellulose recovery rate of 95.5 % and hemicellulose removal rate of 92.7 %. Excellent enzymatic hydrolysis was accomplished with a glucose yield of 99.7 %. Moreover, the crude lactic acid demonstrated acceptable pretreatment and enzymatic hydrolysis performance even after three repeated cycles. This not only effectively utilizes the pretreatment solution, but also offers insights into biomass pretreatment using other fermentable acids.

Life cycle assessment of bioproducts from bamboo residues with biphasic phenoxyethanol-acid based biorefinery technology

Utilizing bamboo residues to produce decarbonization energy products or materials diverts wastes from low-value treatment and supports the circular bioeconomy at the same time. This study develops a cradle-to-grave life-cycle assessment (LCA) for a biorefinery converting bamboo residues into bioproducts (ethanol, polylactic acid (PLA), and bio-based wood adhesive) in China. To combat the low enzymatic hydrolysis performance of bamboo residues and valorize the lignin, this study adopts a biphasic pretreatment by coupling phenoxyethanol and sulfuric acid solution (1%) to achieve high fermentable sugar production. The LCA study is coupled with a process simulation for an industrial-scale biorefinery based on the experimental data. Our results show that the life-cycle Global Warming Potential (GWP) is 17.0–32.1 gCO2e/MJ for ethanol cases and 3.2–3.7 kgCO2e/kg for PLA cases, when biphasic pretreatment is adopted. The lower GWP values are achieved by using 1:1 phenoxyethanol: acid solution, though it has a lower product yield than 4:1 phenoxyethanol: acid solution cases. Without biphasic pretreatment, the GWP is 135.8 gCO2e/MJ ethanol and 4.4 kgCO2e/kg PLA. For the perspective of treating 1 dry t bamboo residues, with biphasic pretreatment, the GWP is −174 to −66 kgCO2e for ethanol cases and −542 to −432 kgCO2e for PLA cases. The lower GWP is also from using 1:1 phenoxyethanol: acid solution (1%). These GWP ranges are lower than conventional landfilling (2969 kgCO2e) and landfilling with landfill gas recovery (−28 kgCO2e).

Time-Course Carbohydrate-Active Enzyme Production of Neofusicoccum Parvum and its Enzymatic Hydrolysis Performance on Wheat Straw and Grapevine Canes

Time-Course Carbohydrate-Active Enzyme Production of Neofusicoccum Parvum and its Enzymatic Hydrolysis Performance on Wheat Straw and Grapevine Canes

Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads

Steam explosion pretreatment is suitable for bioethanol production from Eucalyptus globulus wood. Multifactorial experiment designs were used to find the optimal temperature and residence time required to obtain the best glucose yield from the enzymatic hydrolysis of pretreated materials. The chemical composition, crystallinity index, morphology and polymerization degree of the pretreated materials were correlated with enzymatic accessibility. Simultaneous saccharification and fermentation (SSF) using a fed-batch strategy was applied to three different laboratory-scale fermenters. The optimization of the pretreatment was obtained at 208 °C and 11 min. However, the enzymatic hydrolysis performance did not show significant differences from the material obtained at 196 °C and 9.5 min, which was determined to be the real optimum, owing to its lower energy requirement. The vertical fermenter with type “G” blades and the horizontal fermenter with helical blades were both highly efficient for reaching ethanol yields close to 90% based on dry wood, and ethanol concentrations close to 9.0% v/v.

Selectively fractionate hemicelluloses with high molecular weight from poplar thermomechanical pulp by tetramethylammonium hydroxide

Selective fractionation of hemicelluloses is of great significance for realizing high-value application of hemicelluloses and comprehensive utilization of lignocellulosic biomass. Tetramethylammonium hydroxide (TMAH) solvent has been confirmed as a promising solvent to selectively fractionate hemicelluloses from holocellulose. Herein, TMAH solvent was adopted to pretreat poplar thermomechanical pulp (PTMP) for the selective fractionation of hemicelluloses and enhancement of enzymatic hydrolysis performance of residues. The maximal hemicelluloses yield (65.0 %) and excellent cellulose retention rate (93.3 %) were achieved after pretreatment by the 25 wt% TMAH solvent, while the delignification was only 33.9 %. The hemicelluloses fractions could be selectively fractionated with high molecular weights (109,800–118,500 g/mol), the contents of Klason lignin in them were low (3.2–5.9 %), and the dominating structure of them was 4-O-methylglucurono-β-D-xylan. Compared to the H2SO4 and NaOH methods, the hemicelluloses fractionated by TMAH method exhibited higher yields, more complete structures and higher molecular weights. Furthermore, the crystalline structure of cellulose practically remained stable, and the highest yield of enzymatic hydrolysis glucose was 57.5 %, which was 3.3 times of that of PTMP. The fractionation effectiveness of TMAH solvent was not significantly reduced after repeatedly recycling. This work demonstrated TMAH solvent could selectively fractionate hemicelluloses from PTMP and efficiently promote sustainable poplar-based biorefinery.

Enhancing biomass conversion: Efficient hemicellulose removal and cellulose saccharification in poplar with FeCl3 coupled with acidic electrolyzed water pretreatment

Due to the recalcitrant structure of woody biomass such as poplar, the efficient disassembly and separation of hemicellulose component from woody biomass is crucial for green biomass processing and full component utilization. This study presented an environmentally friendly approach to utilize acidic electrolyzed water (AEW) combined with metal salts and investigated its pretreatment effects on hemicellulose removal and cellulose and lignin retention under different conditions. Meanwhile, the structural properties and enzymatic hydrolysis performance of the pretreated residues were also characterized. As a result, under the optimized pretreatment conditions (0.03 mol/L FeCl3 with AEW at 180 °C for 10 min), hemicellulose removal from poplar wood reached 98.64 %, accompanied by xylose recovery rate of 98.46 %, cellulose retention rate of 93.43 % and lignin retention rate of 94.29 %. Enzymatic hydrolysis rate of the pretreated cellulose-enriched substrate reached 97.65 %. Furthermore, comprehensive structural characterizations revealed that FeCl3 coupled with AEW pretreatment resulted in surface damage to the poplar wood, effective removal of the amorphous hemicellulose component, and partial destruction of the cellulose crystallinity. In conclusion, FeCl3 coupled with AEW pretreatment effectively separates hemicellulose, leading to significant alterations in biomass composition and structure, ultimately resulting in improved enzymatic digestion. These results provide theoretical support for targeted dissociation of hemicellulose and full component utilization of woody biomass.

Comprehensive insights into hydrothermal pretreatment of rice straw from physicochemical structure, organic matter transformation and hydrolysate reuse

Anaerobic digestion is an effective means of biomass utilization from solid waste, but the complex structure and low biodegradability of lignocellulose severely limit the anaerobic degradation conversion efficiency. In this study, hydrothermal pretreatment combined with chemicals was conducted to investigate physicochemical structure, chemical composition and changes, and enzymatic hydrolysis performance of rice straw under various combination hydrothermal pretreatment. The transformation mechanism of main components during alkaline-thermal pretreatment and the potential reuse of hydrolysate were further explored. Results showed that the total sugar concentration after hydrothermal pretreatment was 1.49 times higher than that after dissolution pretreatment. Hydrothermal-KOH pretreatment could destroy the waxy and siliceous layer on the straw surface. The roughness increased from 0.525 to 1.170 nm, and the average pore size 6.20 to 8.99 nm. Alkaline-thermal pretreatment could facilitate lignin dissolution and retained more cellulose and hemicellulose in the solid phase, and sugar concentration after pretreatment could reach 40.82 g/L. Porosity was affected by the dissolution of chemicals, and the pore structure also affected subsequent enzymatic hydrolysis. Dissolution of cellulose and hemicellulose resulted in a reduction in particle size and the formation of micropores, while re-aggregation and precipitation of lignin after dissolution led to the pore collapse and an increase in pore size. Furthermore, the hydrolysates contained nutrients, humic acids, plant hormones, and micronutrients, which had the potential to be developed into foliar fertilizers and reused. The results of this study will provide new insights and technical support for high-value utilization of straw.

Extraction of lignin from sugarcane trash and its potency as biosurfactant

Sugarcane trash (SCT) is an environmental concern in Indonesia. The chemical compositions of SCT can be used as benign materials, such as lignin-based biosurfactants, for improving enzymatic hydrolysis performance through the biorefinery concept, yet no one has worked on this. Therefore, the crux of this study is to evaluate lignin and lignin-based biosurfactant characteristics from two different acid-alkali extraction methods: microwave (SCT-A) and autoclave (SCT-B). Both extraction methods successfully isolated lignin with a total lignin content of 82 % and 25 % for SCT-A and 73 % and 35 % for SCT-B, respectively. Lignin was successfully processed into biosurfactant by grafting method, which was proved by ester groups in biosurfactants at 1700 cm−1 from FTIR and δC 163.9–164.4 ppm from 13C NMR. Lignin-based SCT-A can reduce water surface tension up to 50.2 mN/m from 58.8 mN/m (pure water), while the lignin-based SCT-B was 54.4 mN/m. Further studies are required to evaluate the effectiveness of lignin-based biosurfactants in enzymatic hydrolysis.

Performance of high solids enzymatic hydrolysis and bioethanol fermentation of food waste under the regulation of saponin

Bioethanol recovery from food waste through high solids enzymatic hydrolysis (HSEH) and high solids bioethanol fermentation (HSBF) alleviate the energy crisis. However, this cause decreased glucose and bioethanol yields due to the high solids content. In this study, saponin was introduced into food waste HSEH and HSBF systems to enhance the product yields. Under the regulation of saponin, the substrate released >90% of the theoretical reducing sugar. The glucose concentration increased by 137.41 g/L after 24 h of HSEH with 2.0% saponin. The bioethanol titer reached 73.2 g/L (1.0%-saponin). Untargeted metabolomics illustrating that saponin had higher antifungal properties at lower concentrations (0.5%-saponin) that caused a decrease in bioethanol yield. The addition of saponin concentrations of 1.0%∼3.0% promoted HSEH, HSBF, and the metabolism of Saccharomyces cerevisiae; thus, 1.0% was suggested for practical use. This study deepened the understanding of saponin in enhancing HSBF and provides theoretical support for further application.

Mechanism of enhanced enzymatic hydrolysis performance by ethanol assisted deep eutectic solvent pretreatment- from the perspective of lignin

Valorization of lignocellulose has received a lot of attention due to the abundance of lignocellulosics. It was showed that synergistic carbohydrate conversion and delignification could be achieved via ethanol assisted DES (choline chloride/lactic acid) pretreatment. To explore the reaction mechanism of lignin in the DES, milled wood lignin obtained from Broussonetia papyrifera was subjected to pretreatment at critical temperatures. The results suggested that ethanol assistance could contribute the incorporation of ethyl groups and reduce condensation structures of Hibbert’s ketone. Adding ethanol at 150 °C not only decreased formation of condensed G unit (from 7.23% to 0.87%), but also removed J and S’ substructures, thus effectively reducing the adsorption of lignin on cellulase, and promoting the glucose yield after enzymatic hydrolysis.

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

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.

Biobutanol production from cocoa pod husk through a sequential green method: Depectination, delignification, enzymatic hydrolysis, and extractive fermentation

The effect of various treatments on the production of reducing sugar and biobutanol from cocoa pod husk (CPH) through depectination, delignification, enzymatic hydrolysis, and fermentation was studied to obtain the best strategy for sequential processes to valorize CPH to biobutanol. Surfactants of Tween 80, Polyethylene Glycol (PEG) 6000, and Sodium Dodecyl Sulfate (SDS) was added to enhance the performance of enzymatic hydrolysis, and L-cysteine addition to support fermentation by Clostridium saccharoperbutylacetonicum N1–4. The optimum activity of the cellulase was at 0.25 FPU/g. Depectination, microwave-assisted delignification, and 2.5 g/L PEG 6000 addition sequence produced the highest sugar concentration of 9.24 g/L. The highest butanol and acetone-butanol-ethanol (ABE) concentrations of 20.4 g/L and 54.4 g/L, respectively, were obtained using immobilized cells and L-cysteine supplementation. ABE production by extractive fermentation was enhanced using immobilized cells and L-cysteine supplementation.

RETRACTED ARTICLE: Preparation of carrierized cellulase Cellulase@MIL-88B(Fe) and its enzymatic properties

We, the Editors and Publisher of Green Chemistry Letters and Reviews have retracted the following article: Erhong Zhang, Meng Wang, Xiaoliang Pan, Xinfeng Wang & Wenju Zhang (2022) Preparation of carrierized cellulase Cellulase@MIL-88B(Fe) and its enzymatic properties, Green Chemistry Letters and Reviews, 15:3, 627-637, DOI: https://doi.org/10.1080/17518253.2022.2124890 Following publication, the authors requested the withdrawal of this article in 2022 due to a conflict with an associated patent. Further investigations by the Publisher, in close collaboration with the Editor-in-Chief, could not confirm a conflict with an associated patent but revealed that the article has significant overlap with a chapter of an unpublished thesis titled “Construction of an adaptive immobilized cellulase system and its enzymatic hydrolysis performance” authored by Tiantian Li in June 2022. More specifically, the overlap involves most of the data in the article which was reused without the required permissions, or the knowledge of the owners of the data. Upon query, the authors have cooperated with the investigation, but could neither demonstrate that their data was obtained appropriately, nor that their study was conducted in compliance with our editorial policies. As the reuse of data from a third-party without acquiring the required permissions is a serious breach of publishing ethics, we are retracting the article from the journal. The corresponding author listed in this publication has been informed. We have been informed in our decision-making by our editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Effect of Surfactant HLB Value on Enzymatic Hydrolysis of Chitosan

Nonionic surfactants are reported as being able to enhance enzyme stability and increase the conversion of enzymatic reactions. Surfactant-assisted enzymatic hydrolysis conversion is affected by surfactant HLB values. This work investigated the influence of nonionic surfactants with different HLB values on chitosan enzymatic hydrolysis using cellulase enzyme by measuring the reducing sugars formation, viscosity, and molecular weight of hydrolyzed chitosan. A characterization analysis of hydrolyzed products was also carried out. A higher HLB value exhibits a better enzymatic chitosan hydrolysis performance, shown by the decrease in a solution’s viscosity and the increase in reducing sugar formation. Increasing the surfactant concentration will also increase the hydrolysis rate. Nonionic surfactants can protect cellulase enzyme from the denaturation of temperature and stirring influence. The higher the HLB value, the lower the molecular weight of the hydrolyzed chitosan. The result of UV–Vis demonstrated aldehyde groups formation during hydrolysis. The SEM analysis showed that the chitosan, hydrolyzed using different HLB values of surfactants, had different surface morphologies. However, it did not change the chemical structure of the hydrolysis product seen by the FTIR analysis. The XRD patterns showed that the relative crystallinity of raw chitosan decreased when hydrolyzed with surfactants.

Multifactorial effects of gluconic acid pretreatment of waste straws on enzymatic hydrolysis performance

The chemical compositions of lignin, hemicellulose and cellulose are so far unascertained to various lignocellulose in respect to effect of cellulose enzymatic hydrolysis. The novel and environment-friendly gluconic acid (GA) pretreatment technology showed impressive results on the enzymatic hydrolysis of cellulose in various agricultural straws. However, only few of the main reasons or critical issues pertaining to this reaction are known. Therefore, the novel GA pretreatment was carried out to remove hemicellulose from the three representative waste straws under different conditions. Next, for the enzymatic hydrolysis of the residual cellulose fraction in the pretreated straws, some mathematical correlations have been investigated between enzyme accessibility, hemicellulose removal rate, and cellulose crystallinity index. Both linear and nonlinear models were compared using five-parameter logic curve, four-parameter logic curve, and Deming regression. Hemicellulose removal was logically ascribed to be the trigger for cellulose saccharification efficiency during GA pretreatment of these waste straws.

Fusion of Chitin-Binding Domain From Chitinolyticbacter meiyuanensis SYBC-H1 to the Leaf-Branch Compost Cutinase for Enhanced PET Hydrolysis.

Polyethylene terephthalate (PET) is a mass-produced petroleum-based non-biodegradable plastic that contributes to the global plastic pollution. Recently, biocatalytic degradation has emerged as a viable recycling approach for PET waste, especially with thermophilic polyester hydrolases such as a cutinase (LCC) isolated from a leaf-branch compost metagenome and its variants. To improve the enzymatic PET hydrolysis performance, we fused a chitin-binding domain (ChBD) from Chitinolyticbacter meiyuanensis SYBC-H1 to the C-terminus of the previously reported LCCICCG variant, demonstrating higher adsorption to PET substrates and, as a result, improved degradation performance by up to 19.6% compared to with its precursor enzyme without the binding module. For compare hydrolysis with different binding module, the catalytic activity of LCCICCG-ChBD, LCCICCG-CBM, LCCICCG-PBM and LCCICCG-HFB4 were further investigated with PET substrates of various crystallinity and it showed measurable activity on high crystalline PET with 40% crystallinity. These results indicated that fusing a polymer-binding module to LCCICCG is a promising method stimulating the enzymatic hydrolysis of PET.