Enzymatic Saccharification Efficiency Research Articles

Supercritical CO2 as effective wheat straw pretreatment for subsequent mild fractionation strategies

The efficient utilization of lignocellulosic biomass in biorefineries is pivotal for the transition to a carbon–neutral society, emphasizing the need for environmentally friendly fractionation techniques. While the extensive use of chemicals in biorefinery operations can yield favorable quantities of specific biomass components, adopting less chemically intense conditions is crucial for holistic methodologies that preserve the inherent potential of all biomass constituents. This study comprehensively investigates the use of supercritical carbon dioxide (sc-CO2) as a green pretreatment to improve subsequent mild fractionation on wheat straw. Sc-CO2 at 300 bars, 100 °C and 70 % moisture was found to have minimal impact on the chemical composition and the lignin structure, while there were significant morphological changes as heightened surface area and reduced density. Apart from increasing enzymatic saccharification efficiency, the treatment notably enhanced subsequent mild delignification through alkaline and flow-through organosolv extractions. The combination of the pretreatments enhances the lignin solubilization yields from 49 to 79 % for alkaline and 74 to 91 % for organosolv extractions, while retaining a high β-O-4 conservation of 49 and 59 linkages per 100 aromatic units, respectively. Additionally, the combined use of sc-CO2 with mild dilute acid pretreatment improved xylose solubilization from 59 to 76 % and enzymatic saccharification from 53 to 90 %, albeit with increased lignin condensation. In summary, this study demonstrates the potential of sc-CO2 pretreatment as a versatile tool for biomass valorization within the evolving bioeconomy, by combining enhanced extraction yields with minimal lignin structural impact. Our work thereby highlights the promise of the use of sc-CO2 to contribute to the overall economic potential of improved biorefinery processes.

Salt stress alters the cell wall components and structure in Miscanthus sinensis stems.

Miscanthus is a perennial grass suitable for the production of lignocellulosic biomass on marginal lands. The effects of salt stress on Miscanthus cell wall composition and its consequences on biomass quality have nonetheless received relatively little attention. In this study, we investigated how exposure to moderate (100 mM NaCl) or severe (200 mM NaCl) saline growing conditions altered the composition of both primary and secondary cell wall components in the stems of 15 Miscanthus sinensis genotypes. The exposure to stress drastically impacted biomass yield and cell wall composition in terms of content and structural features. In general, the observed compositional changes were more pronounced under severe stress conditions and were more apparent in genotypes with a higher sensitivity towards stress. Besides a severely reduced cellulose content, salt stress led to increased pectin content, presumably in the form of highly branched rhamnogalacturonan type I. Although salt stress had a limited effect on the total lignin content, the acid-soluble lignin content was strongly increased in the most sensitive genotypes. This effect was also reflected in substantially altered lignin structures and led to a markedly reduced incorporation of syringyl subunits and p-coumaric acid moieties. Interestingly, plants that were allowed a recovery period after stress ultimately had a reduced lignin content compared to those continuously grown under control conditions. In addition, the salt stress-induced cell wall alterations contributed to an improved enzymatic saccharification efficiency.

Developing a new ethylene glycol/H2O pretreatment system to achieve efficient enzymatic hydrolysis of sugarcane bagasse cellulose and recover highly active lignin: Countercurrent extraction

Improving pretreatment efficiency is a critical premise in achieving efficient biomass conversion, and obtaining high-performance natural polymers is the guarantee of high-value conversion of biomass. In this study, a new pilot-scale continuous countercurrent pretreatment reaction unit about ethylene glycol-alkali solution was designed for pretreating sugarcane bagasse in order to achieve efficient separation of the three major components of lignocellulose when expanding the scale of pretreatment, reduce lignin deposition on the fiber surface, and obtain highly active lignin and excellent enzymatic hydrolysis efficiency of cellulose. X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), brunauer-emmett-teller (BET) and scanning electron microscope (SEM) methods are used to analyze the structural properties of sugarcane bagasse before and after pretreatment, and high-performance liquid chromatography (HPLC) is used to analyze the monosaccharide components in the enzymatic solution. In addition, the structural properties of the recovered lignin are analyzed by gel permeation chromatography (GPC), 31P NMR and 2D-HSQC-NMR methods. The results indicate that the system can gain a high cellulose recovery of 92.99 % along with a lignin removal of 95.33 %, and recovered lignin has low lignin carbohydrate complexes, low condensation, and rich in phenolic hydroxyl groups for 1.95 mmol/g. Meanwhile, the countercurrent pretreatment system can effectively reduce the deposition of lignin on the cellulose surface, which is evidently superior to the non-countercurrent pretreatment and facilitates the efficiency of enzymatic saccharification of substrate, achieving a high glucose yield of 99% as well as a total sugar yield of 91.11 %. The method efficiently separates biomass in a green manner, and solid residues are easily hydrolyzed, showing potential for industrial-scale production.

In situ pretreatment of wood samples with deep eutectic solvents for enhanced lignin removal and enzymatic Saccharification efficiency optimization

Deep eutectic solvents (DESs) are commonly utilized as an effective pretreatment method for biomass materials, particularly for enhancing the value of lignocellulosic biomass. However, to the best of our knowledge, the utilization of DESs for in situ pretreatment of wood samples has been seldom reported. In this study, the ability of five DESs systems to in-situ pretreatment of balsa wood samples was investigated. Among of them, the Choline Chloride-Ethylene Glycol-P-Toluenesulfonic Acid (ChCl-EG-PTSA) system showing an excellent lignin removal rate (the lignin removal of 87.34 % and cellulose retention of 86.32 %), which is significantly better than the delignification effect of the traditional acid chlorite method (lignin removal of 72,13 % and cellulose retention of 64.57 %). In addition, in the subsequent enzymatic saccharification experiments, after the wood samples were pretreated in situ by the ChCl-EG-PTSA system, the enzymatic saccharification yield of cellulose reached 75.46 %, and the enzymatic saccharification yield of xylose reached 92 %. At the same time, this study also used SEM, FTIR, XPS, TGA and other testing technologies to conduct detailed analysis and characterization of the pretreated samples. This comprehensive analysis unequivocally demonstrated the viability of the ChCl-EG-PTSA system as an environmentally sustainable and efficient approach for pretreating forest biomass. Significantly, this in-situ wood pretreatment strategy significantly lays a robust research groundwork for the development of multifunctional wood fiber composites in subsequent stages.

Efficient enzymatic saccharification of agricultural wastes for the production of bioethanol, D-allulose and lactic acid

The demand for renewable resources to replace fossil fuels has increased. Fruit and agricultural wastes can be fermented to yield biofuels and biochemicals. However, the high cost of the feedstock and limitations of the catalytic process hinder the application of such wastes. Therefore, we aimed to develop an efficient enzymatic saccharification process, without pretreatment, for fruit and agricultural wastes. The conversion rate of the mixed agricultural wastes (MAW) to fermentable sugars was approximately 91 % after 24 h. The ethanol yield increased by 4.5 % after limonene removal. The D-allulose yield in the hydrolysate was 4.6 mg/mL at 4 °C and 3.3 mg/mL at 50 °C, whereas the fructose yield in the sugar medium was 13.2 mg/mL at 4°C, demonstrating a high conversion yield of 73.2 %. Lactic acid was produced at a conversion rate of approximately 67.4 %. Therefore, this study presents a novel approach of the biosynthesis of functional sugars and chemicals from waste biomass, introducing a cost-effective enzymatic saccharification process that bypasses pretreatment, thereby enabling the production of biofuels, biochemicals, and functional sugars and opening up a promising economic opportunity in the field.

The multiple enhancements of deep eutectic solvent on cellulase significantly improve the saccharification efficiency of lignocellulosic biomass

The introduction of specific choline chloride (ChCl)- and betaine (Bet)-based deep eutectic solvents (DESs) into the conventional acetic acid–sodium acetate solution led to a significant increase in cellulase activity and stability. In particular, a higher enhancement in β-glucosidase activity was obtained, which plays a key role in improving cellulase function. The DESs prolonged the half-life of cellulase. The addition of 10 % (v/v) ChCl/1,3-propanediol (1:2) and 5 % (v/v) Bet/glycerol (1:2) resulted in the most significant improvement, with the half-life of cellulase reaching three times the initial half-life value. The above both DESs allowed the cellulase to maintain an excellent level of activity over time, even after 72 h. The DESs tightened the structure of the enzyme by changing its secondary structure, which had a stabilizing effect on the overall conformation. The density functional theory calculations of DESs revealed that the DES with a more stable structure more effectively protected the active conformation. The molecular dynamics simulation on β-glucosidase indicated that the hydrogen bond donor end of the DES primarily formed hydrogen bonds with the enzyme, which induced a spatially compact conformation by increasing the α-helix content while reducing the β-sheet content. It also restricted the movement of amino acids, particularly stabilizing the active site, and increased the hydrophilic region, thereby enhancing enzyme activity and stability. In addition, the DES formed a protective layer that prevented the unproductive adsorption of lignin on the enzymes during the hydrolysis of lignocellulosic feedstocks. These multiple improvements provided by DESs significantly increased the enzymatic saccharification efficiency of corn stover and poplar.

Salt stress alters the cell wall components and structure in Miscanthus sinensis stems.

Miscanthus is a perennial grass suitable for the production of lignocellulosic biomass on marginal lands. The effects of salt stress on Miscanthus cell wall composition and its consequences on biomass quality have nonetheless received relatively little attention. In this study, we investigated how exposure to moderate (100 mM NaCl) or severe (200 mM NaCl) saline growing conditions altered the composition of both primary and secondary cell wall components in the stems of 15 Miscanthus sinensis genotypes. The exposure to stress drastically impacted biomass yield and cell wall composition in terms of content and structural features. In general, the observed compositional changes were more pronounced under severe stress conditions and were more apparent in genotypes with a higher sensitivity towards stress. Besides a severely reduced cellulose content, salt stress led to increased pectin content, presumably in the form of highly branched rhamnogalacturonan type I. Although salt stress had a limited effect on the total lignin content, the acid-soluble lignin content was strongly increased in the most sensitive genotypes. This effect was also reflected in substantially altered lignin structures and led to a markedly reduced incorporation of syringyl subunits and p-coumaric acid moieties. Interestingly, plants that were allowed a recovery period after stress ultimately had a reduced lignin content compared to those continuously grown under control conditions. In addition, the salt stress-induced cell wall alterations contributed to an improved enzymatic saccharification efficiency.

Sulfomethylation reactivity enhanced the Fenton oxidation pretreatment of bamboo residues for enzymatic digestibility and ethanol production.

Bamboo is considered a renewable energy bioresource for solving the energy crisis and climate change. Dendrocalamus branddisii (DB) was first subjected to sulfomethylation reaction at 95°C for 3h, followed by Fenton oxidation pretreatment at 22°C for 24h. The synergistic effect of combined pretreatment dramatically improved enzymatic digestibility efficiency, with maximum yield of glucose and ethanol content of 71.11% and 16.47g/L, respectively, increased by 4.7 and 6.11 time comparing with the single Fenton oxidation pretreatment. It was found that the hydrophobicity of substrate, content of surface lignin, degree of polymerization, and specific surface area have significant effects on the increase of enzymatic saccharification efficiency. It also revealed that sulfomethylation pre-extraction can improve the hydrophilicity of lignin, leading to the lignin dissolution, which was beneficial for subsequent Fenton pretreatment of bamboo biomass. This work provides some reference for Fenton oxidation pretreatment of bamboo biomass, which can not only promote the utilization of bamboo in southwest China, but also enhances the Fenton reaction in the bamboo biorefinery.

Stable cellulolytic activity of Clostridium thermocellum against cellulosic biomass pretreated with ionic liquid 1-ethyl 3-methylimidazolium acetate

Using cellulosic biomass has considerable potential for the production of valuable chemicals while contributing to carbon neutrality. This study investigates the effect of biomass pretreatment with ionic liquid 1-ethyl 3-methylimidazolium acetate ([EMIM][Ac]) on the efficiency of enzymatic saccharification using the cellulolytic system of the thermophilic bacterium Clostridium thermocellum. Although [EMIM][Ac] pretreatment improves the efficiency of enzymatic saccharification, it also inhibits the cellulolytic enzyme. Following incubation with 30 % [EMIM][Ac], while the cellulolytic activity of the commercial cellulase cocktail (Celluclast) decreased to 15 % and that of C. thermocellum exoproteome remained stable, suggesting a relative tolerance of C. thermocellum cellulases to [EMIM][Ac]. The reducing sugars released from the pretreated cellulosic biomass corn hull by Celluclast were reduced by 24 % with supplementation of 5 % [EMIM][Ac] but remained unchanged for C. thermocellum exoproteome. These results highlight the potential of [EMIM][Ac] pretreatment of cellulosic biomass as a promising approach for enzymatic saccharification using C. thermocellum.

Co-production of pigment and high value-added bacterial nanocellulose from Suaeda salsa biomass with improved efficiency of enzymatic saccharification and fermentation

This study evaluated the co-production of pigment and bacterial nanocellulose (BNC) from S. salsa biomass. The extraction of the beet red pigment reduced the salts and flavonoids contents by 82.7%–100%, promoting the efficiencies of enzymatic saccharification of the biomass and the fermentation of BNC from the hydrolysate. SEM analysis revealed that the extraction process disrupted the lignocellulosic fiber structure, and the chemical analysis revealed the lessened cellulase inhibitors, consequently facilitating enzymatic saccharification for 10.4 times. BNC producing strains were found to be hyper-sensitive to NaCl stress, produced up to 400.4% more BNC from the hydrolysate after the extraction. The fermentation results of BNC indicated that the LDU-A strain yielded 2.116 g/L and 0.539 g/L in ES-M and NES-M, respectively. In comparison to the control, the yield in ES-M increased by approximately 20.0%, while the enhancement in NES-M was more significant, reaching 292.6%. After conducting a comprehensive characterization of BNC derived from S. salsa through Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA), the average fiber diameter distribution of these four BNC materials ranges from 22.23 to 33.03 nanometers, with a crystallinity range of 77%–90%. Additionally, they exhibit a consistent trend during the thermal degradation process, further emphasizing their stability in high-temperature environments and similar thermal properties. Our study found an efficient co-production approach of pigment and BNC from S. salsa biomass. Pigment extraction made biomass more physically and chemically digestible to cellulase, and significantly improved BNC productivity and quality.

Natural lignin modulators improve bagasse saccharification of sugarcane and energy cane in field trials

AbstractThe burgeoning cellulosic ethanol industry necessitates advancements in enzymatic saccharification, effective pretreatments for lignin removal, and the cultivation of crops more amenable to saccharification. Studies have demonstrated that natural inhibitors of lignin biosynthesis can enhance the saccharification of lignocellulose, even in tissues generated several months post‐treatment. In this study, we applied daidzin (a competitive inhibitor of coniferaldehyde dehydrogenase), piperonylic acid (a quasi‐irreversible inhibitor of cinnamate 4‐hydroxylase), and methylenedioxy cinnamic acid (a competitive inhibitor of 4‐coenzyme A ligase) to 60‐day‐old crops of two conventional Brazilian sugarcane cultivars and two energy cane clones, bred specifically for enhanced biomass production. The resultant biomasses were evaluated for lignin content and enzymatic saccharification efficiency without additional lignin‐removal pretreatments. The treatments amplified the production of fermentable sugars in both the sugarcane cultivars and energy cane clones. The most successful results softened the most recalcitrant lignocellulose to the level of the least recalcitrant of the biomasses tested. Interestingly, the softest material became even more susceptible to saccharification.

Long term study of cell wall saccharification and high added value phenolic acids production from Phalaris aquatica L. energy crop

Phalaris aquatica L. is a cool-season perennial grass of the Mediterranean that has been used for forage production, while recently was identified as a novel candidate for sustainable second-generation bioethanol production. This study provides for the first time evidence about this energy crop long-term performance (five years of growth), the cell wall saccharification efficiency and the production of high added value compounds during this period. High biomass production was recorded constantly after the first year of plant growth, with a maximum of 22.4 ± 0.5 t of dry mass (DM) per ha and stable structural polysaccharides concentration 68.8% ± 0.8 w/w DM from the third year on. Independently from crop age, dilute acid pretreatment (120 °C, 1.5% H2SO4, 45 min) promoted the subsequent enzymatic hydrolysis of P. aquatica L. biomass. The dilute acid pre-treatment positive effect is attributed both to the hemicellulose solubilization and the breakage of intermolecular bonds between polysaccharides and phenolic acids, as supported by the present study results These combined acid/enzymatic hydrolysis processes were able to convert more than 80% of cell wall polysaccharides into fermentable sugars, releasing simultaneously a substantial amount of phenolic acids of 2.16% ± 0.48 w/w DM. The ratio of ferulic to p-coumaric acid in the acid hydrolysate can be used for the prediction of the subsequent cellulose enzymatic saccharification efficiency, by the model described here. The protocatechuic acid, which can find many technological applications, was the main bioactive polyphenol in the final hydrolysate with concentration ∼1% w/w DM. These results are supportive of Phalaris aquatica L. suitability as a sustainable biorefinery crop, under the semi-arid Mediterranean climatic conditions contributing to this region biodiversity and prosperity.

Effective hydrothermal-enzymatic sequential process of agave bagasse enhances saccharification and methane production

The efficiency of enzymatic saccharification of lignocellulosic biomass is a key step for biofuels production in the biochemical biorefineries. A novel sequential process, hydrothermal pretreatment followed by enzymatic hydrolysis, of agave bagasse was investigated to improve the release of sugars and the methane production. After optimization of the hydrothermal pretreatment by surface response methodology, a hemicellulose removal of 93.6% was obtained at 180 °C/50 min. Hemicellulose removal enhanced cellulose depolymerization during the enzymatic hydrolysis of the pretreated bagasse by 2.3 times as compared to the untreated bagasse. The single-stage batch methane production of the hydrothermal and enzymatic hydrolysates were 0.223 ± 0.02 NL CH4/ g CODadd and 0.305 ± 0.03 NL CH4/g CODadd respectively, indicating a higher biodegradability of the enzymatic hydrolysate. The combined energy recovered from the hydrothermal and enzymatic hydrolysates was 3.4 times greater than that recovered from untreated agave bagasse hydrolysate. Also, the combined energy recovery was higher than the energy recovery reported in the literature for agave bagasse pretreated with other chemical and hydrothermal pretreatments. Overall, this study enhanced the saccharification efficiency and biodegradability of polysaccharides present in agave bagasse through efficient saccharification of cellulose and hemicellulose. This was reflected in a high value of combined energy recovery efficiency (54.1%) in the form of methane.

Exploration of separate hydrolysis and fermentation and simultaneous saccharification and co-fermentation for acetone, butanol, and ethanol production from combined diluted acid with laccase pretreated Puerariae Slag in Clostridium beijerinckii ART44

In this study, an efficient pretreatment technology was developed for the bioconversion of puerariae slag (PS) into biobutanol. To accelerate the enzymatic saccharification of PS, the method of dilute acid combined with laccase pretreatment (DALP) was performed. With this effort, the highest concentration of reducing sugar was 48.96 ± 1.69 g/L after enzymatic hydrolysis of the whole slurry pretreatment under the optimal condition. Subsequently, the highest butanol productivity (0.15 g/L/h) was obtained by the simultaneous saccharification and co-fermentation (SSCF), which was 114.29% higher than that of the separate hydrolysis and fermentation (SHF). Furthermore, the microstructural changes of PS after different pretreatment were initially investigated by FT-IR, and we found that the DALP method resulted in more severe damage during the pretreatment process, which could improve the efficiency of enzymatic saccharification. This study suggests that the DALP is an attainable and efficient pretreatment method for production of butanol in the SSCF process.

Effects of various persulfate oxidation pretreatments on enzymatic saccharification efficiency of sugarcane bagasse biomass and the related mechanism

This study explored the impact of different persulfate pretreatments on the substrate characteristics and enzymatic sugar yield of sugarcane bagasse (SCB) and the related mechanisms. We analyzed the biomass composition, physicochemical properties of SCB, enzymatic saccharification efficiency, pure commercial cellulose and lignin degradation dynamics, and ·OH and SO4∙ − generation properties under different persulfate pretreatments. The results revealed that potassium peroxymonosulfate (2KHSO5·KHSO4·K2SO4, PPMS) pretreatment had a significant effect on SCB. Under the optimal pretreatment conditions, SCB pretreated with PPMS showed a reducing sugar yield of 67.98%, a sugar conversion rate of 90.29%, and a lignin removal rate of 87.49%, which were about 2–3 folds those under pretreatment with peroxydisulfate (PDS) including sodium persulfate (Na2S2O8, SPS) and ammonium persulfate ((NH4)2S2O8, APS). PPMS had higher selectivity for lignin degradation and stronger free radical generation ability than PDS, which may be the main contributor to its superior pretreatment performance.

Integrated process to produce biohydrogen from wheat straw by enzymatic saccharification and dark fermentation

In this study, different pretreatment methods, including lyophilization, hydrothermal pretreatment, and ultrasound combined with dilute alkali post-cooking, were investigated to enhance the efficiency of enzymatic saccharification and biohydrogen production of the wheat straw. All pretreatment methods could effectively remove lignin and hemicellulose while retaining cellulose, further enhancing the biomass accessibility for subsequently enzymatic saccharification and biohydrogen production. A reducing sugar concentration of 13.18 g/L was acquired when wheat straw was treated with ultrasound and dilute alkali cooking (RU). The sequential fermentative hydrogen yield of the substrate RU was 133.6 mL/g total solids (TS), which was 5.6-fold larger than that of the raw material (23.9 mL/g TS). The study confirmed that ultrasound combined with dilute alkali cooking was an effective method, which not only provided significant guideline for improving biohydrogen production but also presented helpful direction for the efficient pretreatment of other lignocellulosic biomass.

Degradation of lignin in different lignocellulosic biomass by steam explosion combined with microbial consortium treatment

The difficulty of degrading lignin is the main factor limiting the high-value conversion process of lignocellulosic biomass. The biodegradation of lignin has attracted much attention because of its strong environmental friendliness, but it still faces some dilemmas such as slow degradation rate and poor adaptability. The microbial consortia with high lignin degradation efficiency and strong environmental adaptability were obtained in our previous research. To further increase the lignin degradation efficiency, this paper proposes a composite treatment technology of steam explosion combined with microbial consortium degradation to treat three kinds of biomass. We measured the lignin degradation efficiency, selectivity value (SV) and enzymatic saccharification efficiency. The structural changes of the biomass materials and microbial consortium structure were also investigated. The experimental results showed that after 1.6 MPa steam explosion treatment, the lignin degradation efficiency of the eucalyptus root reached 35.35% on the 7th days by microbial consortium. At the same time, the lignin degradation efficiency of the bagasse and corn straw treated by steam explosion followed by microbial biotreatment was 37.61–44.24%, respectively, after only 7 days of biotreatment. The microbial consortium also showed strong selectivity degradation to lignin. The composite treatment technology can significantly improve the enzymatic saccharification efficiency. Saccharomycetales, Ralstonia and Pseudomonadaceae were the dominant microorganisms in the biomass degradation systems. It was proved that the combined treatment technology of steam explosion and microbial consortium degradation could overcome the drawbacks of traditional microbial pretreatment technology, and can facilitate the subsequent high-value conversion of lignocellulose.

Transgenic ZmMYB167 Miscanthus sinensis with increased lignin to boost bioenergy generation for the bioeconomy

BackgroundPerennial C4 grasses from the genus Miscanthus are widely regarded as leading and promising dedicated bioenergy crops due to their high biomass accumulation on marginal land with low environmental impacts and maintenance requirements over its productive life. There is an urgent socio-political and environmental need to ramp up the production of alternative, affordable and green bioenergy sources and to re-direct the net zero carbon emissions trajectory. Hence, up-scaling of Miscanthus cultivation as a source of biomass for renewable energy could play an important role to strategically address sustainable development goals for a growing bio-based economy. Certain Miscanthus sinensis genotypes are particularly interesting for their biomass productivity across a wide range of locations. As the aromatic biomass component lignin exhibits a higher energy density than cell wall polysaccharides and is generally used as an indicator for heating or calorific value, genetic engineering could be a feasible strategy to develop M. sinensis biomass with increased lignin content and thus improving the energetic value of the biomass.ResultsFor this purpose, transgenic M. sinensis were generated by Agrobacterium-mediated transformation for expression of ZmMYB167, a MYB transcription factor known for regulating lignin biosynthesis in C3 and C4 grasses. Four independent transgenic ZmMYB167 Miscanthus lines were obtained. Agronomic traits such as plant height, tillering and above-ground dry weight biomass of the transgenic plants were not different to that of wild-type control plants. Total lignin content of the transgenic plants was ~ 15–24% higher compared with control plants. However, the structural carbohydrates, glucan and xylan, were decreased by ~ 2–7% and ~ 8–10%, respectively, in the transgenic plants. Moreover, expression of ZmMYB167 in transgenic plants did not alter lignin composition, phenolic compounds or enzymatic saccharification efficiency yields but importantly improved total energy levels in Miscanthus biomass, equivalent to 10% higher energy yield per hectare.ConclusionsThis study highlights ZmMYB167 as a suitable target for genetic lignin bioengineering interventions aimed at advancing and developing lignocellulosic biomass supply chains for sustainable production of renewable bioenergy.

Efficient fermentable sugar production from mulberry branch based on a rational design of GH10 xylanase with improved thermal stability

The mulberry branch can be used as a renewable biomass resource for the production of biofuels since it contains a significant amount of lignocellulose. However, the rapid deactivation of enzymes during lignocellulose degradation in a high-temperature environment leads to high costs and low efficiency of enzymatic saccharification. In this study, xylanase was modified by rational design, and xylanase and cellulase were used to synergistically degrade mulberry branches pretreated with seawater. The fermentable sugar yield and degree of synergy (DS) were determined. The dominant mutant S21Y/N318W of Hortaea werneckii xylanase Hwxyl10A was obtained with improved thermostability (T50 increased by 12 °C, t1/2 is 17-fold that of WT). Meanwhile, the specific activity at 75 °C increased from 1470 to 1901 U/mg. Under the condition of seawater immersion pretreatment, the highest yield of fermentable sugar was 313.5 μmol/g, and the highest DS was 1.57 after enzymatic hydrolysis of mulberry branches by cellulase and S21Y/N318W at 50 °C. Therefore, the biotransformation of mulberry branches reducing sugar has been significantly improved, which provides an efficient method of biomass saccharification for biofuel production.

Converting textile waste into value-added chemicals: An integrated bio-refinery process

The rate of textile waste generation worldwide has increased dramatically due to a rise in clothing consumption and production. Here, conversion of cotton-based, colored cotton-based, and blended cotton-polyethylene terephthalate (PET) textile waste materials into value-added chemicals (bioethanol, sorbitol, lactic acid, terephthalic acid (TPA), and ethylene glycol (EG)) via enzymatic hydrolysis and fermentation was investigated. In order to enhance the efficiency of enzymatic saccharification, effective pretreatment methods for each type of textile waste were developed, respectively. A high glucose yield of 99.1% was obtained from white cotton-based textile waste after NaOH pretreatment. Furthermore, the digestibility of the cellulose in colored cotton-based textile wastes was increased 1.38–1.75 times because of the removal of dye materials by HPAC-NaOH pretreatment. The blended cotton−PET samples showed good hydrolysis efficiency following PET removal via NaOH–ethanol pretreatment, with a glucose yield of 92.49%. The sugar content produced via enzymatic hydrolysis was then converted into key platform chemicals (bioethanol, sorbitol, and lactic acid) via fermentation or hydrogenation. The maximum ethanol yield was achieved with the white T-shirt sample (537 mL/kg substrate), which was 3.2, 2.1, and 2.6 times higher than those obtained with rice straw, pine wood, and oak wood, respectively. Glucose was selectively converted into sorbitol and LA at a yield of 70% and 83.67%, respectively. TPA and EG were produced from blended cotton−PET via NaOH–ethanol pretreatment. The integrated biorefinery process proposed here demonstrates significant potential for valorization of textile waste.