Hydrolysis Of Corn Stalk Research Articles

Producing D-Ribose from D-Xylose by Demonstrating a Pentose Izumoring Route.

D-Ribose plays fundamental roles in all living organisms and has been applied in food, cosmetics, health care, and pharmaceutical sectors. At present, D-ribose is predominantly produced by microbial fermentation based on the pentose phosphate pathway (PPP). However, this method suffers from a long synthetic pathway, severe growth defect of the host cell, and carbon catabolite repression (CCR). According to the Izumoring strategy, D-ribose can be produced from D-xylose through only three steps. Being not involved in the growth defect or CCR, this shortcut route is promising to produce D-ribose efficiently. However, this route has never been demonstrated in engineering practice, which hinders its application. In this study, we stepwise demonstrated this route and screened out higher active enzymes for each step. The first D-ribose production from D-xylose through the Izumoring route was achieved. By stepwise enzyme dosage tuning and process optimization, 6.87 g/L D-ribose was produced from 40 g/L D-xylose. Feeding D-xylose further improved the D-ribose titer to 9.55 g/L. Finally, we tested the coproduction of D-ribose and D-allose from corn stalk hydrolysate using the route engineered herein. In conclusion, this study demonstrated a pentose Izumoring route, complemented the engineering practices of the Izumoring strategy, paved the way to produce D-ribose from D-xylose, and provided an approach to comprehensively utilize the lignocellulosic sugars.

Effect of carboxylated and quaternized lignin and epoxidized lignin on enzymatic hydrolysis of corn stalk

Lignin structure is known to have significant effects on the enzymatic hydrolysis efficiency (EHE) of lignocellulose. In this study, the lignin produced from corn stalk pretreated with p-toluenesulfonic acid (PCS) was used to prepare carboxylated and quaternized lignin (CQCL) and epoxidized lignin (ECL), and the effect of the two modified lignin forms on the EHE of PCS was investigated. The results showed that EHE after adding CQCL (83.7%) was higher than adding ECL (60.8%). To explore the reasons, the unproductive adsorption, cellulase-lignin interaction, and molecular dynamics experiments were conducted. The results showed that the smaller hydrophobic interaction and electrostatic attraction between CQCL and cellulase caused less unproductive adsorption between CQCL and cellulase than ECL. Additionally, CQCL and ECL changed differently the conformations of key amino acid residues of cellobiohydrolase I and endoglucanase II, which was also responsible for the higher EHE after adding CQCL.

Engineering Corynebacterium glutamicum for de novo production of 2-phenylethanol from lignocellulosic biomass hydrolysate

Background2-Phenylethanol is a specific aromatic alcohol with a rose-like smell, which has been widely used in the cosmetic and food industries. At present, 2-phenylethanol is mainly produced by chemical synthesis. The preference of consumers for “natural” products and the demand for environmental-friendly processes have promoted biotechnological processes for 2-phenylethanol production. Yet, high 2-phenylethanol cytotoxicity remains an issue during the bioproduction process.ResultsCorynebacterium glutamicum with inherent tolerance to aromatic compounds was modified for the production of 2-phenylethanol from glucose and xylose. The sensitivity of C. glutamicum to 2-phenylethanol toxicity revealed that this host was more tolerant than Escherichia coli. Introduction of a heterologous Ehrlich pathway into the evolved phenylalanine-producing C. glutamicum CALE1 achieved 2-phenylethanol production, while combined expression of the aro10. Encoding 2-ketoisovalerate decarboxylase originating from Saccharomyces cerevisiae and the yahK encoding alcohol dehydrogenase originating from E. coli was shown to be the most efficient. Furthermore, overexpression of key genes (aroGfbr, pheAfbr, aroA, ppsA and tkt) involved in the phenylpyruvate pathway increased 2-phenylethanol titer to 3.23 g/L with a yield of 0.05 g/g glucose. After introducing a xylose assimilation pathway from Xanthomonas campestris and a xylose transporter from E. coli, 3.55 g/L 2-phenylethanol was produced by the engineered strain CGPE15 with a yield of 0.06 g/g xylose, which was 10% higher than that with glucose. This engineered strain CGPE15 also accumulated 3.28 g/L 2-phenylethanol from stalk hydrolysate.ConclusionsIn this study, we established and validated an efficient C. glutamicum strain for the de novo production of 2-phenylethanol from corn stalk hydrolysate. This work supplied a promising route for commodity 2-phenylethanol bioproduction from nonfood lignocellulosic feedstock.Graphical

Employing Cationic Kraft Lignin as Additive to Enhance Enzymatic Hydrolysis of Corn Stalk.

A water-soluble cationic kraft lignin (named JLQKL50), synthesized by combining quaternization and crosslinking reactions, was used as an additive to enhance the enzymatic hydrolysis of dilute-alkali-pretreated corn stalk. The chemical constitution of JLQKL50 was investigated by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR) and 13C NMR spectroscopy, and elemental analysis. The enzymatic hydrolysis efficiency of corn stalk at solid content of 10% (w/v) was significantly improved from 70.67% to 78.88% after 24 h when JLQKL50 was added at a concentration of 2 g/L. Meanwhile, the enzymatic hydrolysis efficiency after 72 h reached 91.11% with 10 FPU/g of cellulase and 97.92% with 15 FPU/g of cellulase. In addition, JLQKL50 was found capable of extending the pH and temperature ranges of enzymatic hydrolysis to maintain high efficiency (higher than 70%). The decrease in cellulase activity under vigorous stirring with the addition of JLQKL50 was 17.4%, which was much lower than that (29.7%) without JLQKL50. The addition of JLQKL50 reduced the nonproductive adsorption of cellulase on the lignin substrate and improved the longevity, dispersity, and stability of the cellulase by enabling electrostatic repulsion. Therefore, the enzymatic hydrolysis of the corn stalk was enhanced. This study paves the way for the design of sustainable lignin-based additives to boost the enzymatic hydrolysis of lignocellulosic biomass.

Produce D-allulose from non-food biomass by integrating corn stalk hydrolysis with whole-cell catalysis.

D-allulose is a high-value rare sugar with many health benefits. D-allulose market demand increased dramatically after approved as generally recognized as safe (GRAS). The current studies are predominantly focusing on producing D-allulose from either D-glucose or D-fructose, which may compete foods against human. The corn stalk (CS) is one of the main agricultural waste biomass in the worldwide. Bioconversion is one of the promising approach to CS valorization, which is of significance for both food safety and reducing carbon emission. In this study, we tried to explore a non-food based route by integrating CS hydrolysis with D-allulose production. Firstly we developed an efficient Escherichia coli whole-cell catalyst to produce D-allulose from D-glucose. Next we hydrolyzed CS and achieved D-allulose production from the CS hydrolysate. Finally we immobilized the whole-cell catalyst by designing a microfluidic device. Process optimization improved D-allulose titer by 8.61 times, reaching 8.78g/L from CS hydrolysate. With this method, 1kg CS was finally converted to 48.87g D-allulose. This study validated the feasibility of valorizing corn stalk by converting it to D-allulose.

Molybdenum oxide decorated Ru catalyst for enhancement of lignin oil hydrodeoxygenation to hydrocarbons

Herein, the catalysts of ruthenium and molybdenum oxide nanoparticles supported on activated carbon (AC) were synthesized by precursor stepwise impregnation and employed for the hydrodeoxygenation (HDO) of lignin oil. The XRD, TEM, XPS and NH3-TPD-MS result of RuMoOx/AC catalysts confirm that the method of loading molybdenum precursor before ruthenium precursor is advantageous for the MoOx and Ru nanoparticles high dispersion and the reduction of MoOx species enhance the amount of acidity of catalyst. Meanwhile, the reduction temperature of RuMoOx/AC-1-T catalysts could effectively regulate the MoOx species that determine the activity and product distribution of HDO. The conversion of aromatic monomers/dimers were up to 96% with high selectivity of hydrocarbon over RuMoOx/AC-1-350 catalyst at 160 °C and 30 bar H2. Which is attributed to the MoO3 and Ru species possess the excellent activity of benzene ring deep hydrogenation, ether bond breaking and acid dehydration. The RuMoOx/AC-1-350 catalyst effectively converted lignin oil (from the depolymerization of cornstalk hydrolysis residue) into hydrocarbons (56.9 wt%) and cyclohexanol/ethers (18.7 wt%) under 280 °C and 3 bar H2. The durability of the RuMoOx/AC-1-350 catalyst for HDO of lignin oil was also investigated and showed that the RuMoOx/AC-1-350 catalyst had good stability, regenerability and repeatability.

Development of a general kinetic model for organic acid-catalyzed hydrolysis of corn stalk

Development of a general kinetic model for organic acid-catalyzed hydrolysis of corn stalk

Role of residue cornstalk derived biochar for the enhanced bio-hydrogen production via simultaneous saccharification and fermentation of cornstalk

Biochar derived from residue cornstalk left after anaerobic bio-hydrogen production (RCA-biochar) was confirmed to enhance bio-hydrogen production from cornstalk hydrolysate. However, the role of RCA-biochar in simultaneous saccharification and fermentation (SSF) during bio-hydrogen production from cornstalk has not yet been revealed. This study therefore aims to fill this knowledge gap. It was observed that with the increase in RCA-biochar concentration from 0 g/L to 10.0 g/L, the maximal cumulative SSF bio-hydrogen yield varied from 24.3 ± 1.1 mL/g-substrate to 154.3 ± 3.6 mL/g substrate under varying pH values – 5.5, 6.0, 6.5, 7.0. The increasing bio-hydrogen production was observed to correlate with both RCA-biochar level and initial pH. Batch tests confirmed that the initial pH had an obvious effect an saccharification, while RCA-biochar affected anaerobic fermentation a lot. The findings revealed the role of previously unrecognized RCA-biochar in SSF bio-hydrogen production from cornstalk, which can provide an alternative approach for lignocellulosic bio-hydrogen production.

Photo-biological hydrogen production by a temperature-tolerant mutant of Rhodobacter capsulatus isolated by transposon mutagenesis

Screening of high temperature tolerant strains is important for photo-fermentative hydrogen production in natural conditions which exhibit wide temperature variations. Hence, a temperature-tolerant strain of Rhodobacter capsulatus was isolated by transposon mutagenesis. The mutant strain Rhodobacter capsulatus MX01 could convert cornstalk hydrolysate into hydrogen successfully, and exhibited better hydrogen production performance at higher culture temperature (33 °C and 37 °C) and light intensity (5000 lx and 7000 lx) than the wild type strain. At 33 °C and 5000 lx, the total hydrogen production yield and rate of MX01 from cornstalk hydrolysate were 3.64 ± 0.18 mol-H2/g-cornstalk and 40.07 ± 1.70 mmol-H2/(h·g-cornstalk), respectively. The energy conversion efficiency of cornstalk hydrolysate to hydrogen for the mutant strain MX01 was 10.6%. This higher temperature- and light intensity-tolerant mutant MX01 could carry out photo-fermentation at outdoor settings, which is important for eco-friendly, low-cost and energy-saving practical application of bio-hydrogen production.

Effect of Rhodococcus sp. pretreatment on cellulose hydrolysis of corn stalk

Pretreatment can improve the hydrolysis efficiency of cellulose, in which biological pretreatment plays an important role. In the present study, we uncovered that Rhodococcus has the ability of lignin degradation, which can decompose lignin and serve as a carbon source to meet the needs of its own growth. We used Rhodococcus to pretreat the corn stalks and evaluate the effect on cellulose hydrolysis. The concentration of reducing sugar produced by the hydrolysis of corn stalk after pretreatment of Rhodococcus is 2.95 g/L. SEM imaging showed that Rhodococcus pretreatment resulted the surface of corn stalk to be no longer complete, some lamellar structures fall off, and leave obvious traces, and obvious delamination was found at the edge of the fault. AFM imaging showed that the pretreatment changed the lignin structure of the corn stalk material surface, resulting in a higher surface roughness of 9.37. These results indicated that Rhodococcus pretreatment can improve the saccharification efficiency of cellulose by removing lignin and increasing the surface roughness of the material.

Tyrosinase inhibitory performance of hydrolysate from post-washing liquor of steam exploded corn stalk and its fractionation enhancement

In this work, corn stalk was subjected to steam explosion (SE) pretreatment, and the hydrolysate in post-washing liquor of steam exploded corn stalk was assayed for anti-tyrosinase activity for the first time. The hydrolysate showed strong anti-tyrosinase activity with an IC50 of 2.17 mg/mL (inhibitor concentration when 50% of tyrosinase activity is inhibited) at SE severity of 4.20 (198 °C, 20 min). Through hydrolysate component profiles and model substance analysis, phenolic compounds (especially lignin-derived H-unit monomers and phenolic acids) were confirmed to be the major tyrosinase inhibitors in hydrolysate. To further improve the inhibitory activity, an enrichment process of phenolic compounds by ethyl-acetate fractionation of hydrolysate was employed. Ethyl-acetate soluble fraction exhibited significantly enhanced anti-tyrosinase activity (IC50, 0.29 mg/mL), which was even better than p-coumaric acid (a typical tyrosinase inhibitor with IC50 of 0.31 mg/mL). Additionally, the mixed-type inhibition of hydrolysate on tyrosinase was illustrated by kinetics study and the interaction between hydrolysate and tyrosinase was confirmed by fluorescence quenching measurement. Consequently, this work aims to evaluate and improve the anti-tyrosinase activity of hydrolysate from steam explosion processing of corn stalk, which opens new perspectives in potential application of currently underused corn stalk hydrolysate as a value-added tyrosinase inhibitor.

Feasibility of enhancing hydrogen production from cornstalk hydrolysate anaerobic fermentation by RCPH-biochar

This study presents a novel approach based on addition of biochar generated from residue of cornstalk left after pretreatment and hydrolysis (RCPH-biochar) to improve hydrogen production from cornstalk hydrolysate. RCPH-biochar at concentration of 15 g L−1 substantially enhanced hydrogen generation during batch tests, with the highest cumulative hydrogen volume (3990 mL L−1) being 1.7 times that without RCPH-biochar. Then, continuous hydrogen production performance demonstrated that RCPH-biochar was capable of retaining biomass in the reactor, at 6 h hydraulic retention time, hydrogen production rate (22.8 mmol H2 L−1 h−1) was tripled compared to the control, meanwhile, glucose and xylose utilization reached to 82.3% and 54.6%, respectively. Overall material balance indicates continuous hydrogen production with RCPH-biochar enabled 63.4% higher cornstalk transfer to H2 and 53.3% more cornstalk utilization. The findings reported is a closed-loop process and is economically and environmentally attractive, which might support comprehensive cornstalk utilization with less energy input in the future.

The effect of Ru/C and MgCl2 on the cleavage of inter- and intra-molecular linkages during cornstalk hydrolysis residue valorization

The cleavage of linkages of lignocellulose is important for its valorization. The linkage cleavage of cornstalk hydrolysis residue was investigated over catalysts (Ru/C + MgCl2) in EtOAc/H2O solvents. The results show that almost hydrogen bonds, C–C bonds, ether and ester bonds in the matrix of lignin and cellulose were broken, accompanying 80.6% of lignin and 98.5% of cellulose conversion, and obtaining 37.5% of aromatic monomers and 28.8% of lignin oligomers. In the reaction system, biphasic EtOAc/H2O solvents exhibited an effect on cleaving the intermolecular linkages between lignin and cellulose. MgCl2 showed limited abilities of breaking the α-O-4 and β-O-4 linkages in lignin and limited β-1, 4-glycosidic and hydrogen bonds in cellulose were cleaved over Ru/C catalyst. The cleavage of C–O linkages (α-O-4, β-O-4, 4-O-5) and C–C bonds (α-β, β-5) in lignin were mainly dependent on Ru/C catalyst. Much C–O and the stubborn C–C linkages of β-5, β-1 and 5-5 were significantly disrupted by the synergistic effect between MgCl2 and Ru/C. However, MgCl2 exhibited great contribution to breakage of β-1, 4-glycosidic linkage, hydrogen bonds and sugar ring of cellulose. The linkage of β-1, 4-glycosidic, hydrogen bonds and C–C in C5/C6 sugars were significantly broken. The increased yield of products was evidently due to the synergistic effect of Ru/C combined with MgCl2.

Enhanced bio-hydrogen production from cornstalk hydrolysate pretreated by alkaline-enzymolysis with orthogonal design method

Bio-hydrogen (H2) production from renewable biomass has been accepted as a promising method to produce an alternative fuel for the future. In this study, fermentative hydrogen production from cornstalk (CS) hydrolysate pretreated by alkaline-enzymolysis method was investigated. Meanwhile, a five-factor and five-level orthogonal experimental array was designed to study the influences of Ca(OH)2 concentration, alkaline hydrolysis time, alkaline hydrolysis temperature, cellulase and xylanase dosages on cornstalk pretreatment and hydrogen production. A maximum reducing sugar yield of 0.59 g/g-CS was obtained at Ca(OH)2 0.5%, hydrolysis temperature 115 °C, hydrolysis time 1.5 h, cellulase dosage 4000 U/g-CS and xylanase 4000 U/g-CS. Under this same condition, the maximum hydrogen yields of 168.9 mL/g-CS, 357.6 mL/g-CS, and 424.3 mL/g-CS were obtained at dark-fermentation, photo-fermentation, and two-stage fermentation respectively. It's also found that the significance of these five parameters on H2 production followed from high to low order as: Ca(OH)2 concentration, cellulase dosage, xylanase dosage, hydrolysis time, and hydrolysis temperature. By comparing the energy produced with the energy spent, the maximum Energy Sustainability Index (ESI) value of 1.11 was obtained at the two-stage fermentation. The results suggested that two-stage fermentation is a promising and efficient way for hydrogen production from lignocellulosic biomass.

Effect of cornstalk hydrolysis on photo-fermentative hydrogen production by R. capsulatus

Cornstalk is a typical cellulose material, which can be used by photo-fermentative H2 production after pretreatment. However, the pretreatment methods have different influence on photo fermentation. In this study, 25.0 g cornstalk was pretreated by HCl/NaOH/cellusase. The hydrolysis rates increased from 45.51% by ddH2O-treatment to 60.79% by diluted HCl-treatment and 51.6% by NaOH-treatment. The corresponding reducing sugar yields were 0.13 g/g, 0.42 g/g and 0.01 g/g, respectively. Enzymatic treatment enhanced the corresponding cornstalk hydrolysis rates to 50.81%, 67.60% and 64.10% with reducing sugar yields of 0.22 g/g, 0.62 g/g and 0.26 g/g. The sorts and concentrations of carbon source for H2 production vary among different hydrolysates. Photo-fermentative H2 production of strain R. capsulatus JL1 and mutant JL1601 (cheR2-) with hydrolysates were investigated. The maximum H2 yield of 123.8 ± 14.2 mL/g by strain JL1 was obtained from alkali-enzyme pretreated cornstalk, while the H2 yield of 224.9 ± 5.2 mL/g by mutant JL1601 (cheR2-) was obtained with acid-enzyme hydrolysate as the substrates. Meanwhile, the alkali pretreated cornstalk was the worst for photo-fermentation of both strain JL1 and mutant JL1601 (cheR2-). Nevertheless, the highest substrate conversion efficiencies for both strains were obtained from ddH2O-pretreated hydrolysate. Two-step pretreated hydrolysates were more beneficial to H2 production for mutant JL1601 (cheR2-) but not for strain JL1.

Engineering Microbial Consortia for High-Performance Cellulosic Hydrolyzates-Fed Microbial Fuel Cells.

Microbial fuel cells (MFCs) are eco-friendly bio-electrochemical reactors that use exoelectrogens as biocatalyst for electricity harvest from organic biomass, which could also be used as biosensors for long-term environmental monitoring. Glucose and xylose, as the primary ingredients from cellulose hydrolyzates, is an appealing substrate for MFC. Nevertheless, neither xylose nor glucose can be utilized as carbon source by well-studied exoelectrogens such as Shewanella oneidensis. In this study, to harvest the electricity by rapidly harnessing xylose and glucose from corn stalk hydrolysate, we herein firstly designed glucose and xylose co-fed engineered Klebsiella pneumoniae-S. oneidensis microbial consortium, in which K. pneumoniae as the fermenter converted glucose and xylose into lactate to feed the exoelectrogens (S. oneidensis). To produce more lactate in K. pneumoniae, we eliminated the ethanol and acetate pathway via deleting pta (phosphotransacetylase gene) and adhE (alcohol dehydrogenase gene) and further constructed a synthesis and delivery system through expressing ldhD (lactate dehydrogenase gene) and lldP (lactate transporter gene). To facilitate extracellular electron transfer (EET) of S. oneidensis, a biosynthetic flavins pathway from Bacillus subtilis was expressed in a highly hydrophobic S. oneidensis CP-S1, which not only improved direct-contacted EET via enhancing S. oneidensis adhesion to the carbon electrode but also accelerated the flavins-mediated EET via increasing flavins synthesis. Furthermore, we optimized the ratio of glucose and xylose concentration to provide a stable carbon source supply in MFCs for higher power density. The glucose and xylose co-fed MFC inoculated with the recombinant consortium generated a maximum power density of 104.7 ± 10.0 mW/m2, which was 7.2-folds higher than that of the wild-type consortium (12.7 ± 8.0 mW/m2). Lastly, we used this synthetic microbial consortium in the corn straw hydrolyzates-fed MFC, obtaining a power density 23.5 ± 6.0 mW/m2.

Efficient Xylitol Production from Cornstalk Hydrolysate Using Engineered Escherichia coli Whole Cells.

Economic transformation of lignocellulose hydrolysate into valued-added products is of particular importance for energy and environmental issues. In this study, xylose reductase and glucose dehydrogenase were cloned into plasmid pETDuet-1 and then simultaneously expressed in Escherichia coli BL21(DE3), which was used as whole-cell catalyst for the first time to convert xylose into xylitol coupled with gluconate production. When tested with reconstituted xylose and glucose solution, 0.1 g/mL cells could convert 1 M xylose and 1 M glucose completely and produced 145.81 g/L xylitol with a yield of 0.97 (g/g) and 184.85 g/L gluconic acid with a yield of 1.03 (g/g) in 24 h. Subsequently, the engineered cells were applied in real cornstalk hydrolysate, which generated 30.88 g/L xylitol and 50.89 g/L gluconic acid. The cells were used without penetration treatment, and CaCO3 was used to effectively regulate the pH during the production, which further saved costs.

Effects of ionic liquid/water mixture pretreatment on the composition, the structure and the enzymatic hydrolysis of corn stalk

Recently, pretreatment of lignocellulose by ionic liquids have attracted considerable attention due to their excellent pretreatment effects and their environmental sustainable properties. However, because of the high cost and viscosity, their industrial application are restricted. In this study, water was introduced to 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) to reduce both the viscosity and the cost of using pure ionic liquid. The [Bmim]BF4/water system was proved to be effective for improving the enzymatic hydrolysis of corn stalk, and the enzymatic hydrolysis efficiency (81.68%) obtained was much higher than that found with the pure ionic liquid under the same conditions (14.46%). The findings obtained from the characterization studies were in accordance with the enhancement of the hydrolysis of the lignocellulosic biomass. After pretreated by [Bmim]BF4-H2O, the formation of a porous structure, destruction of the lignin-polysaccharide interactions, and deacetylation of hemicellulose were achieved as suggested by SEM, FTIR and 13C NMR, respectively, but the crystalline structure was not damaged indicated by XRD results.

Metabolic engineering of Corynebacterium glutamicum for efficient production of succinate from lignocellulosic hydrolysate

BackgroundSuccinate has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. However, efficient methods for the production of succinate from lignocellulosic feedstock were rarely reported. Nevertheless, Corynebacterium glutamicum was engineered to efficiently produce succinate from glucose in our previous study.ResultsIn this work, C. glutamicum was engineered for efficient succinate production from lignocellulosic hydrolysate. First, xylose utilization of C. glutamicum was optimized by heterologous expression of xylA and xylB genes from different sources. Next, xylA and xylB from Xanthomonas campestris were selected among four candidates to accelerate xylose consumption and cell growth. Subsequently, the optimal xylA and xylB were co-expressed in C. glutamicum strain SAZ3 (ΔldhAΔptaΔpqoΔcatPsod-ppcPsod-pyc) along with genes encoding pyruvate carboxylase, citrate synthase, and a succinate exporter to achieve succinate production from xylose in a two-stage fermentation process. Xylose utilization and succinate production were further improved by overexpressing the endogenous tkt and tal genes and introducing araE from Bacillus subtilis. The final strain C. glutamicum CGS5 showed an excellent ability to produce succinate in two-stage fermentations by co-utilizing a glucose–xylose mixture under anaerobic conditions. A succinate titer of 98.6 g L−1 was produced from corn stalk hydrolysate with a yield of 0.87 g/g total substrates and a productivity of 4.29 g L−1 h−1 during the anaerobic stage.ConclusionThis work introduces an efficient process for the bioconversion of biomass into succinate using a thoroughly engineered strain of C. glutamicum. To the best of our knowledge, this is the highest titer of succinate produced from non-food lignocellulosic feedstock, which highlights that the biosafety level 1 microorganism C. glutamicum is a promising platform for the envisioned lignocellulosic biorefinery.

Impact of lignin extraction methods on microstructure and mechanical properties of lignin‐based carbon fibers

ABSTRACTIn order to optimize the use of residues of enzymatic hydrolysis of corn stalk (REHCS) and explore the low‐cost and sustainable raw material substitute for carbon fibers, three types of lignin samples were extracted from REHCS by various extraction methods, and then they were converted into carbon fibers (CFs) by electrospinning, thermostabilization, and carbonization under the same process conditions. The microstructure and mechanical properties of the three types of carbonized fibers were different. The CFs from the ethanol organosolv lignin were actually smooth and brittle carbon films. The CFs from the formic acid/acetic acid organosolv lignin had microscopic pores, causing poor mechanical properties. Comparatively, the CFs from the alkaline lignin demonstrated preferable microstructure and mechanical properties. The reasons for the differences were analyzed by characterizing the lignin samples, precursor fibers, and resultant CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45580.