Hydrolysis Of Lignocellulosic Biomass Research Articles

Elucidation of enhanced cellulase immobilization onto synthetic magnetic nickel nanomaterials for lignocellulosic biomass hydrolysis

The immobilization of cellulase enzymes for the conversion of lignocellulosic biomass into sustainable biochemical products is essential for the stability and recovery of the enzymes. In this study, nickel nanoparticles (NiNPs) were synthesized and coated with 3-aminopropyl triethoxysilane (APTES) to serve as cellulase enzyme carriers. Cellulase enzyme immobilization on the prepared NiNPs was achieved using glutaraldehyde as a cross-linker. The physicochemical properties of the carrier were determined before and after enzyme immobilization using X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Vibrating-Sample Magnetometer (VSM), and Field Emission Scanning Electron Microscopy (FESEM). The impacts of different experimental factors on the performance of the cellulase enzymes immobilized on the synthesized NiNPs and commercial nickel nanoparticles were compared. The results showed comparable optimal cellulase enzyme immobilization conditions on both substrates in terms of the immobilization time, pH, and cellulase enzyme concentration. However, the recommended temperatures for cellulase enzyme immobilization on the synthesized and commercial NiNPs were 50 °C and 40 °C, respectively. Under these optimum conditions, the immobilized cellulase enzyme on the synthesized NiNPs had an activity of about 99.1% (in comparison to the activity of free cellulase enzyme), while the activity of the enzyme upon immobilization on commercial NiNPs was about 93%. The particle size of the NiNPs was found to be crucial for enzyme immobilization efficiency and its magnetic strength. Therefore, cellulase enzyme immobilization on tunable NiNPs could be a sustainable and eco-friendly approach towards high recovery of cellulose from lignocellulosic materials.

Effect of Hemicelluloses Fractionated by Graded Ethanol Precipitation from Corn Stover on the Enzymatic Hydrolysis of Lignocellulosic Biomass

Effect of Hemicelluloses Fractionated by Graded Ethanol Precipitation from Corn Stover on the Enzymatic Hydrolysis of Lignocellulosic Biomass

Recovery of sulfuric acid during sugar purification from pretreated wheat straw hydrolysate using electro-electrodialysis system for 2G bioethanol production

Concentrated acid hydrolysis (CAH) of lignocellulosic biomass (LCB) is an established method to obtain a near theoretical yield of monomeric sugars from the biomass. The CAH process produced 83.23 % of glucose from pretreated wheat straw (PWS) at optimum conditions (i.e., stage I = 74 % w/w acid, 1:2 biomass loading, and 50 °C for 1 h; and stage II = 30 % w/w acid, 90 °C for 2 h). However, the separation of sugar from acidic hydrolysate is a major constraint of this technology. In this study, an electro-electrodialysis (EED) process using a novel anion exchange membrane (AEM) has been developed to recover sulfuric acid from biomass hydrolysate. The synthetic hydrolysate (i.e., feed acid concentration = 2 M; glucose = 80 g L−1) was used to optimize the EED process parameters. The acid was successfully recovered from alkali pretreated wheat straw (PWS) hydrolysate using the most effective EED process parameters. This resulted in an 82.72 % acid recovery in the permeate under the following conditions: current density of 88 mA cm−2, flow rate of 3 L h−1, and feed acid content of 2 M. During the EED process, the highest glucose recovery in the feed was 90.98 %, achieved with a maximum current efficiency of 93.57 % and the lowest energy consumption of 0.052 kW h mol−1 at optimal conditions using PWS Hydrolysate. Saccharomyces cerevisiae fermented the acid-free PWS hydrolysate, resulting in a maximum ethanol yield of 92.3 %. The EED process cost of $0.049 kg H2SO4−1 and total revenue was $0.02 kg biomass−1 from the second batch onwards suggest the feasibility of the EED process for large-scale 2G bioethanol productions.

Application of Thermomyces lanuginosus polygalacturonase produced in Komagataella phaffii in biomass hydrolysis and textile bioscouring

In this work, the polygalacturonase (TL-PG1) from the thermophilic fungus Thermomyces lanuginosus was heterologously produced for the first time in the yeast Komagataella phaffii. The TL-PG1 was successfully expressed under the control of the AOX1 promoter and sequentially purified by His-tag affinity. The purified recombinant pectinase exhibited an activity of 462.6 U/mL toward polygalacturonic acid under optimal conditions (pH 6 and 55 ˚C) with a 2.83 mg/mL and 0.063 μmol/minute for Km and Vmax, respectively. When used as supplementation for biomass hydrolysis, TL-PG1 demonstrated synergy with the enzymatic cocktail Ctec3 to depolymerize orange citrus pulp, releasing 1.43 mg/mL of reducing sugar. In addition, TL-PG1 exhibited efficiency in fabric bioscouring, showing potential usage in the textile industry. Applying a protein dosage of 7 mg/mL, the time for the fabric to absorb water was 19.77 seconds (ten times faster than the control). Adding the surfactant Triton to the treatment allowed the reduction of the enzyme dosage by 50% and the water absorption time to 6.38 seconds. Altogether, this work describes a new versatile polygalacturonase from T. lanuginosus with the potential to be employed in the hydrolysis of lignocellulosic biomass and bioscouring.

Engineering yeast to convert lignocellulose into vanillin

Valorizing lignocellulosic biomass (LCB) into platform aromatic chemicals could contribute to a sustainable biomass-based bioeconomy. However, lacking simultaneous bioconversion route of lignin and carbohydrates hinders the LCB utilization. The artificial biological funneling pathway (ABFP) was hence designed to convert full components of LCB into vanillin. The results showed that combinational engineering strategies enabled the successful accumulation of vanillin in Saccharomyces cerevisiae. The funneling pathways of lignin-derived monomers to vanillin were constructed. Enzyme fusion and S-adenosylmethionine metabolism regulation of heterologous rate-limiting enzyme further promoted the vanillin production to 2.49 and 1.94 mmol/L from ferulic acid and p-coumaric acid, respectively. The construction of funneling pathways of hexose and pentose promoted the carbon flux towards vanillin biosynthesis. Together with the regulation of branch and shikimic acid pathways, the microbial cell factory with a novel ABFP produced 1.97 mmol/L vanillin from real LCB hydrolysates with a recorded yield of 10.5 mg vanillin/g carbon source. Overall, the engineered S. cerevisiae simultaneously valorized full components into fine aromatic chemicals, holding the promise to transform biorefinery mode and contribute to the biomass-based economy.

Mixotrophic Syngas Conversion Enables the Production of meso-2,3-butanediol with Clostridium autoethanogenum

Providing simultaneously autotrophic and heterotrophic carbon sources is a promising strategy to overcome the limits of autotrophic syngas fermentations. D-xylose and L-arabinose are particularly interesting as they can be obtained by the hydrolysis of lignocellulosic biomass. The individual conversion of varying initial concentrations of these pentoses and D-fructose as reference was studied with C. autoethanogenum in fully controlled stirred-tank reactors with a continuous syngas supply. All mixotrophic batch processes showed increased biomass and product formation compared to an autotrophic reference process. Simultaneous CO and D-xylose or L-arabinose conversion was observed in contrast to D-fructose. In the mixotrophic batch processes with L-arabinose or D-xylose, the simultaneous CO and sugar conversion resulted in high final alcohol-to-acid ratios of up to 58 g g−1. L-arabinose was superior as a mixotrophic carbon source because biomass and alcohol concentrations (ethanol and 2,3-butanediol) were highest, and significant amounts of meso-2,3-butanediol (>1 g L−1) in addition to D-2,3-butanediol (>2 g L−1) were solely produced with L-arabinose. Furthermore, C. autoethanogenum could not produce meso-2,3 butanediol under purely heterotrophic conditions. The mixotrophic production of meso-2,3-butanediol from L-arabinose and syngas, both available from residual lignocellulosic biomass, is very promising for use as a monomer for bio-based polyurethanes or as an antiseptic agent.

Hydrodynamic studies of innovative membrane reactor for enzymatic hydrolysis of lignocellulosic waste.

This paper presents the study concerning the impact of the basic operational parameters on the performance of an innovative microfiltration membrane reactor applied for enzymatic hydrolysis of lignocellulosic biomass. The concept and basic hydrodynamics of the reactor with tubular ceramic membranes and a propeller agitator were shown. Besides, the efficiency of enzymatic hydrolysis of corn straw was studied to check reactor functionality. It has been proven that the proposed reactor construction can improve the microfiltration of lignocellulosic suspension by reducing the cake layer on the membrane surface. Increasing the rotational speed of the propeller agitator also improved the filtration efficiency. The permeate flux during the microfiltration experiments was lower for smaller lignocellulose biomass fraction (D<425 μm) when compared to the less fragmented corn straw (425<D<900 μm). For larger solid fractions, a stirring speed increase enhanced the separation efficiency regardless of the differences in biomass concentration. In contrast, this trend for the finer biomass fraction was only noticeable for the highest used biomass concentration (C=2.0%). Considering the enzymatic hydrolysis of corn straw, membrane separation of reaction products positively influenced the process yield, and the results depended on the applied operational parameters.

Simultaneous glucose and xylose utilization by an Escherichia coli catabolite repression mutant.

As advances are made toward the industrial feasibility of mass-producing biofuels and commodity chemicals with sugar-fermenting microbes, high feedstock costs continue to inhibit commercial application. Hydrolyzed lignocellulosic biomass represents an ideal feedstock for these purposes as it is cheap and prevalent. However, many microbes, including Escherichia coli, struggle to efficiently utilize this mixture of hexose and pentose sugars due to the regulation of the carbon catabolite repression (CCR) system. CCR causes a sequential utilization of sugars, rather than simultaneous utilization, resulting in reduced carbon yield and complex process implications in fed-batch fermentation. A mutant of the gene encoding the cyclic AMP receptor protein, crp*, has been shown to disable CCR and improve the co-utilization of mixed sugar substrates. Here, we present the strain construction and characterization of a site-specific crp* chromosomal mutant in E. coli BL21 star (DE3). The crp* mutant strain demonstrates simultaneous consumption of glucose and xylose, suggesting a deregulated CCR system. The proteomics further showed that glucose was routed to the C5 carbon utilization pathways to support both de novo nucleotide synthesis and energy production in the crp* mutant strain. Metabolite analyses further show that overflow metabolism contributes to the slower growth in the crp* mutant. This highly characterized strain can be particularly beneficial for chemical production by simultaneously utilizing both C5 and C6 substrates from lignocellulosic biomass.IMPORTANCEAs the need for renewable biofuel and biochemical production processes continues to grow, there is an associated need for microbial technology capable of utilizing cheap, widely available, and renewable carbon substrates. This work details the construction and characterization of the first B-lineage Escherichia coli strain with mutated cyclic AMP receptor protein, Crp*, which deregulates the carbon catabolite repression (CCR) system and enables the co-utilization of multiple sugar sources in the growth medium. In this study, we focus our analysis on glucose and xylose utilization as these two sugars are the primary components in lignocellulosic biomass hydrolysate, a promising renewable carbon feedstock for industrial bioprocesses. This strain is valuable to the field as it enables the use of mixed sugar sources in traditional fed-batch based approaches, whereas the wild-type carbon catabolite repression system leads to biphasic growth and possible buildup of non-preferential sugars, reducing process efficiency at scale.

Dual assistance of surfactants in glycerol organosolv pretreatment and enzymatic hydrolysis of lignocellulosic biomass for bioethanol production

This study investigated an innovative strategy of incorporating surfactants into alkaline-catalyzed glycerol pretreatment and enzymatic hydrolysis to improve lignocellulosic biomass (LCB) conversion efficiency. Results revealed that adding 40 mg/g PEG 4000 to the pretreatment at 195 °C obtained the highest glucose yield (84.6%). This yield was comparable to that achieved without surfactants at a higher temperature (240 °C), indicating a reduction of 18.8% in the required heat input. Subsequently, Triton X-100 addition during enzymatic hydrolysis of PEG 4000-assisted pretreated substrate increased glucose yields to 92.1% at 6 FPU/g enzyme loading. High-solid fed-batch semi-simultaneous saccharification and co-fermentation using this dual surfactant strategy gave 56.4 g/L ethanol and a positive net energy gain of 1.4 MJ/kg. Significantly, dual assistance with surfactants rendered 56.3% enzyme cost savings compared to controls without surfactants. Therefore, the proposed surfactant dual-assisted promising approach opens the gateway to economically viable enzyme-mediated LCB biorefinery.

β-glucosidases from Saccharomyces cerevisiae: production, protein precipitation, characterization, and application in the enzymatic hydrolysis of delignified sugarcane bagasse

β-glucosidase is an essential enzyme for the enzymatic hydrolysis of lignocellulosic biomass, as it catalyzes the final stage of cellulose breakdown, releasing glucose. This paper aims to produce β-glucosidase from Saccharomyces cerevisiae and evaluate the enzymatic degradation of delignified sugarcane bagasse. S. cerevisiae was grown in yeast peptone dextrose medium. Partial purification of the enzyme was achieved through precipitating proteins with ethanol, and the optimal activity was measured by optimizing pH and temperature. The effects of ions, glucose tolerance, and heat treatment were evaluated. Delignified sugarcane bagasse was hydrolyzed by the enzyme. β-glucosidase showed a specific activity of 14.0712 ± 0.0207 U mg−1. Partial purification showed 1.22-fold purification. The optimum pH and temperature were 6.24 and 54 °C, respectively. β-glucosidase showed tolerance to glucose, with a relative activity of 71.27 ± 0.16%. Thermostability showed a relative activity of 58.84 ± 0.91% at 90 °C. The hydrolysis of delignified sugarcane bagasse showed a conversion rate of 87.97 ± 0.10% in the presence of Zn2+, an ion that promoted the highest increase in enzymatic activity. S. cerevisiae produced an extracellular β-glucosidase with good stability at pH and temperatures conventionally applied in the hydrolysis of lignocellulosic biomass, showing viability for industrial application.

Unprecedented glucose production using auto-catalytic hydrothermal hydrolysis of lignocellulosic biomass with no catalyst addition

We propose a novel and simple glucose production method involving autocatalytic hydrothermal hydrolysis of biomass without catalyst additives. This method consists of air-oxidation at a relatively lower temperature than that of the conventional method and subsequent hydrothermal hydrolysis. Japanese cedar (indigestible softwood) was initially air–oxidized by heating at 180–200 °C for 3 h. This induced the decomposition of a small portion of cellulose in the cedar sample, although 93.4 % of cellulose remained at 200 °C. The functional acidic groups (phenol, lactonic, and carboxy groups) specifically increased during the initial air–oxidation. Following this, the acidic groups autocatalytically accelerated hydrothermal cellulose hydrolysis, resulting in a maximum glucose yield of 139.6 mg/g raw material at a severity factor (R0) of 3.2 × 104.

Production of Industrially Important Cellulases and Pectinases using Lignocellulosic Biomass

Cellulases and pectinases are the two main industrially important enzymes that find significant applications in food, feed, pharmaceutical, textile and environmental sectors. In the present study, Trichoderma asperellum S14 was used for enzymes production in liquid state fermentation and for enzymatic hydrolysis of lignocellulosic biomass. Prior to liquid state fermentation, Trichoderma asperellum S14 was qualitatively screened for the pectinolytic and cellulytic activity by using plate assay method. Alkaline pretreatment (1% NaOH) was used for the pretreatment of lignocellulosic biomasses including; wheat bran, wheat straw, rice straw, rice husk and sugarcane bagasse. Maximum cellulase activity of 4.3 U/mL was observed at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated sugarcane bagasse as a substrate. While, maximum pectinase activity 9.2 U/mL obtained at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated wheat bran. Enzymatic hydrolysis was also performed using crude enzymes extract at 50ºC for 72 hours. Maximum hydrolysis (70%) was observed in case of pretreated sugarcane bagasse using Trichoderma asperellum S14 as fungal source for enzyme production. Lignocellulosic biomasses are considered as the best feedstock used in second generation biofuel production because of their renewable resources as well as inexpensive and environment friendly nature. Present study shows the potential of Trichoderma asperellum S14 to degrade variety of lignocellulosic biomass efficiently and could be used to hydrolyze complex lignocellulosic materials towards the production of second generation biofuel.

Characterization of a novel thermostable α-l-arabinofuranosidase for improved synergistic effect with xylanase on lignocellulosic biomass hydrolysis without prior pretreatment

Utilizing thermostable enzymes in biomass conversion processes presents a promising approach to bypass pretreatment, garnering significant attention from the biorefinery industry. A novel discovered α-l-arabinofuranosidase, Abf4980, exhibits exceptional thermostability by maintaining full activity after 24 h of incubation at 70 °C. It effectively acts on polyarabinosides, cleaving α-1,2- and α-1,3-linked arabinofuranose side chains from water-soluble wheat arabinoxylan while releasing xylose. When synergistically combined with the thermostable bifunctional xylanase/β-glucanase CbXyn10C from Caldicellulosiruptor bescii at an enzyme-activity ratio of 6:1, Abf4980 achieves the highest degradation efficiency for wheat arabinoxylan. Furthermore, Abf4980 and CbXyn10C demonstrated remarkable efficacy in hydrolyzing unmodified wheat bran and corn cob to generate arabinose and xylooligosaccharides. This discovery holds promising opportunities for improving the efficiency of lignocellulosic biomass conversion into fermentable sugars.

Exploring the potential of a new thermotolerant xylanase from Rasamsonia composticola (XylRc): production using agro-residues, biochemical studies, and application to sugarcane bagasse saccharification.

Xylanases from thermophilic fungi have a wide range of commercial applications in the bioconversion of lignocellulosic materials and biobleaching in the pulp and paper industry. In this study, an endoxylanase from the thermophilic fungus Rasamsonia composticola (XylRc) was produced using waste wheat bran and pretreated sugarcane bagasse (PSB) in solid-state fermentation. The enzyme was purified, biochemically characterized, and used for the saccharification of sugarcane bagasse. XylRc was purified 30.6-fold with a 22% yield. The analysis using sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed a molecular weight of 53kDa, with optimal temperature and pH values of 80°C and 5.5, respectively. Thin-layer chromatography suggests that the enzyme is an endoxylanase and belongs to the glycoside hydrolase 10 family. The enzyme was stimulated by the presence of K+, Ca2+, Mg2+, and Co2+ and remained stable in the presence of the surfactant Triton X-100. XylRc was also stimulated by organic solvents butanol (113%), ethanol (175%), isopropanol (176%), and acetone (185%). The Km and Vmax values for oat spelt and birchwood xylan were 6.7 ± 0.7mg/mL, 2.3 ± 0.59mg/mL, 446.7 ± 12.7µmol/min/mg, and 173.7 ± 6.5µmol/min/mg, respectively. XylRc was unaffected by different phenolic compounds: ferulic, tannic, cinnamic, benzoic, and coumaric acids at concentrations of 2.5-10mg/mL. The results of saccharification of PSB showed that supplementation of a commercial enzymatic cocktail (Cellic® CTec2) with XylRc (1:1 w/v) led to an increase in the degree of synergism (DS) in total reducing sugar (1.28) and glucose released (1.05) compared to the control (Cellic® HTec2). In summary, XylRc demonstrated significant potential for applications in lignocellulosic biomass hydrolysis, making it an attractive alternative for producing xylooligosaccharides and xylose, which can serve as precursors for biofuel production.

Microfluidic reactor designed for time-lapsed imaging of pretreatment and enzymatic hydrolysis of lignocellulosic biomass

The effect of tissue-specific biochemical heterogeneities of lignocellulosic biomass on biomass deconstruction is best understood through confocal laser scanning microscopy (CLSM) combined with immunohistochemistry. However, this process can be challenging, given the fragility of plant materials, and is generally not able to observe changes in the same section of biomass during both pretreatment and enzymatic hydrolysis. To overcome this challenge, a custom polydimethylsiloxane (PDMS) microfluidic imaging reactor was constructed using standard photolithographic techniques. As proof of concept, CLSM was performed on 60 μm-thick corn stem sections during pretreatment and enzymatic hydrolysis using the imaging reactor. Based on the fluorescence images, the less lignified parenchyma cell walls were more susceptible to pretreatment than the lignin-rich vascular bundles. During enzymatic hydrolysis, the highly lignified protoxylem cell wall was the most resistant, remaining unhydrolyzed even after 48 h. Therefore, imaging thin whole biomass sections was useful to obtain tissue-specific changes during biomass deconstruction.

A Comparison of Dilute Aqueous Isethionic Acid and Sulfuric Acid in Hydrolysis of Three Different Untreated Lignocellulosic Biomass Varieties.

Efficient catalytic hydrolysis of lignocellulosic biomass to sugars is a major challenge in the production of sustainable biofuels and chemical feedstocks. In this study isethionic acid was compared with H2SO4 for hydrolysis of polysaccharides in corn stover, switch grass, and poplar. The catalytic activities of acids were compared by analysis of total reducing sugar (TRS) and glucose yields in a sequence of experiments in water at 90-190 °C using 0.050 mol of H+/L isethionic acid and H2SO4. In comparison to using H2SO4, the use of isethionic acid catalyst lowered the maximum TRS percent yield temperatures by 25, 24, and 21% for corn stover, switch grass, and poplar. A similar effect was observed for glucose percent yields as well. This temperature reduction is due to lowering of the activation energy in the polysaccharide depolymerization reaction and most likely due to hydrogen-bonding-type dipolar interactions between the isethionic acid -OH group and -OH groups in biomass polysaccharides.

Improvement of Laccase Activity in Co-Culture of Panus lecomtei and Sporidiobolus pararoseus and Its Application as an Enzymatic Additive in Biomass Hydrolysis and Dye Decolorization

This work investigates the effects of the co-culture between the filamentous fungus Panus lecomtei and the yeast Sporidiobolus pararoseus in the production of laccases. The variations of time interval and inoculum volume of S. pararoseus in co-cultures with P. lecomtei stimulated laccase production, reaching its highest activity at nearly 2960.7 ± 244 U/mL with a maximum time point of 120 h and 2.0% (v/v), respectively. Further application in the pretreated sugarcane bagasse hydrolysis was performed, using P. lecomtei and S. pararoseus extract added to an enzyme mixture from the co-culture of P. lecomtei and Trichoderma reesei that positively favored the hydrolysis efficiency by 66.87%. Furthermore, the addition of P. lecomtei and S. pararoseus extract increased the degradation of industrial anthraquinone Remazol Brilliant Blue R by 78.98%. As a result, the extract derived from the co-culture of P. lecomtei and S. pararoseus rich in laccases presents potential in biotechnological applications, being suitable in the hydrolysis of lignocellulosic biomass and the degradation of unwanted dyes released in the environment.

Near-complete genome sequence of Lipomyces tetrasporous NRRL Y-64009, an oleaginous yeast capable of growing on lignocellulosic hydrolysates.

Lipomyces tetrasporous is an oleaginous yeast that can utilize a variety of plant-based sugars. It accumulates lipids during growth on lignocellulosic biomass hydrolysates. We present the annotated genome sequence of L. tetrasporous NRRL Y-64009 to aid in its development as a platform organism for producing lipids and lipid-based bioproducts.

Characterization of a novel acidophilic, ethanol tolerant and halophilic GH12 β-1,4-endoglucanase from Trichoderma asperellum ND-1 and its synergistic hydrolysis of lignocellulosic biomass

A novel acidophilic GH5 β-1,4-endoglucanase (TaCel12) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 1.5-fold increase). Deglycosylated TaCel12 migrated as a single band (26.5 kDa) in SDS-PAGE. TaCel12 was acidophilic with a pH optimum of 4.0 and displayed great pH stability (>80 % activity over pH 3.0–5.0). TaCel12 exhibited considerable activity towards sodium carboxymethyl cellulose and sodium alginate with Vmax values of 197.97 μmol/min/mg and 119.06 μmol/min/mg, respectively. Moreover, TaCel12 maintained >80 % activity in the presence of 20 % ethanol and 4.28 M NaCl. Additionally, Mn2+, Pb2+ and Cu2+ negatively affected TaCel12 activity, while the presence of 5 mM Co2+ significantly increased the enzyme activity. Analysis of action mode revealed that TaCel12 required at least four glucose (cellotetraose) residues for hydrolysis to yield cellobiose and cellotriose. Site-directed mutagenesis results suggested that Glu133 and Glu217 of TaCel12 are crucial catalytic residues, with Asp116 displaying an auxiliary function. Production of soluble sugars from lignocellulose is a crucial step in bioethanol development, and it is noteworthy that TaCel12 could synergistically yield fermentable sugars from corn stover and bagasse, respectively. Thus TaCel12 with excellent properties will be considered a potential biocatalyst for applications in various industries, especially for lignocellulosic biomass conversion.

Enhanced tolerance of Clostridium tyrobutyricum to furan derivatives for efficient butyric acid production by overexpressing native transporter genes

Furan aldehydes generated during the hydrolysis of lignocellulosic biomass are toxic to Clostridium tyrobutyricum, severely inhibiting its butyric acid production. This study confirmed that overexpression of the ABC-transporter gene CtAT2 in C. tyrobutyricum significantly increased furfural tolerance (> 3.0 g/L) and butyrate production (13.8 %). Conversely, overexpression of the MFS-transporter gene CtMT1 enhanced tolerance to HMF (> 4.0 g/L). However, co-expression of CtAT2 and CtMT1 in C. tyrobutyricum failed to improve the strain’s tolerance to furfural and HMF. Using undetoxified corncob acid hydrolysate as the carbon source, the recombinant strain ATCC 25755/AT2 exhibited excellent performance in butyric acid fermentation due to its heightened furfural tolerance and improved butyrate production. ATCC 25755/AT2 demonstrated impressive butyrate production and productivity in fed-batch fermentation, reaching 29.8 g/L and 0.23 g/L·h, respectively. These values represented a 22.6 % increase in butyrate production and a 27.8 % increase in productivity compared to the wild-type strain.