Pretreated Corncob Research Articles

Efficient synthesis of 2,5‐furandicarboxylic acid from corncob biomass using Ru/C and sulfonated carbon catalysts in a one‐pot system

AbstractThis study proposes a novel one‐pot method to produce 2,5‐furandicarboxylic acid (FDCA), which effectively simplifies the preparation process of FDCA by directly utilizing the biomass raw material corncob and its derived carbon‐based catalysts. In this work, we first prepared two different carbon‐based catalysts from corncobs: a ruthenium‐supported catalyst (Ru/C) and a sulfonated carbon catalyst. After detailed characterization and performance testing, these two catalysts were used to catalyze the pretreated corncob mixture to produce FDCA. Under optimized conditions, even using 0.12 g of Ru/C catalyst at a microwave power of 200 W, the yield of FDCA can reach 27 mol%. In comparison, the FDCA yield of the sulfonated carbon catalyst under the same conditions was 19 mol%. This work not only demonstrates the possibility of efficient production of FDCA by utilizing biomass resources and a simplified chemical conversion process, but also highlights the importance of selecting appropriate catalysts and controlling reaction conditions in improving yields. Through this method, we can promote the development of biomass conversion technology in a more efficient and environmentally friendly direction, providing technical support for the commercial production of bio‐based chemicals.

Direct Conversion of Minimally Pretreated Corncob by Enzyme-Intensified Microbial Consortia

The presence of diverse carbohydrate-active enzymes (CAZymes) is crucial for the direct bioconversion of lignocellulose. In this study, various anaerobic microbial consortia were employed for the degradation of 10 g/L of minimally pretreated corncob. The involvement of lactic acid bacteria (LAB) and a CAZyme-rich bacterium (Bacteroides cellulosilyticus or Paenibacillus lautus) significantly enhanced the lactic acid production by Ruminiclostridium cellulolyticum from 0.74 to 2.67 g/L (p < 0.01), with a polysaccharide conversion of 67.6%. The supplement of a commercial cellulase cocktail, CTec 2, into the microbial consortia continuously promoted the lactic acid production to up to 3.35 g/L, with a polysaccharide conversion of 80.6%. Enzymatic assays, scanning electron microscopy, and Fourier transform infrared spectroscopy revealed the substantial functions of these CAZyme-rich consortia in partially increasing enzyme activities, altering the surface structure of biomass, and facilitating substrate decomposition. These results suggested that CAZyme-intensified consortia could significantly improve the levels of bioconversion of lignocellulose. Our work might shed new light on the construction of intensified microbial consortia for direct conversion of lignocellulose.

Sustainable biofuels from corncobs: optimization of microwave pretreatment for enhanced fermentable sugar yield

Microwave-Assisted Alkali (MAA) pretreatment of corncob biomass was optimized for maximum fermentable sugar yield using dilute sulfuric acid hydrolysis. A Central Composite Design (CCD) investigated the effects of microwave power (450–9000 W), NaOH concentration (1.5 to 4.5% wt./v), and irradiation time (10–20 min) on lignin removal. The optimal MAA pretreatment conditions were found to be 691.73 W, 3.4% NaOH, and 15.5 min, resulting in the selective removal of 73.36% lignin with high retention of cellulose (71.69%) and hemicellulose (22.14%). Characterization techniques (FTIR, SEM, XRD, TGA) confirmed substantial changes in surface morphology, functional groups, crystallinity, and thermal stability of the pretreated corncobs. Dilute sulfuric acid hydrolysis (0.5–2.5%, 110130 °C, 3060 min) of the optimized sample yielded a maximum reducing sugar output of 537.42 mg/g, achieved at 0.534% H2SO4, 122.3 °C, for 58 min. Optimizing Microwave-Assisted Alkali pretreatment process for corncobs could boost biofuel production efficiency, sustainably utilize agricultural waste, and advance a more sustainable energy landscape.

Preparation of a high-performance conductive lignocellulose hydrogel by directly using non-detoxified bisulfite-pretreated corncob

Biomass-based hydrogels have become a research hotspot because of their better biocompatibility. However, the preparation of biomass hydrogels is complicated, and they often need to be modified by introducing other substances. In this study, corncob pretreated with bisulfite (125–185 °C) was used as a raw material to prepare lignocellulose hydrogels. The results showed that directly using the pretreated sample without the washing step lowered the total hydrogel costs while preserving the lignosulfonate (LS) produced during pretreatment. The best tensile (54.1 kPa) and compressive (177.7 kPa) stresses were obtained for the hydrogel prepared from non-detoxified pretreated corncob at 165 °C (NCH-165). The sulfonic acid groups in LS could enhance the interaction between plant cellulose, thus improving its mechanical properties. The capacitor assembled from NCH-165 achieved an energy density of 236.1 Wh/kg at a power density of 499.7 W/kg and a high coulombic efficiency of more than 99 % after 2000 charge/discharge cycles. In conclusion, the present study simplifies the pathway for the preparation of flexible, conductive, and anti-freezing hydrogels by directly utilizing a non-detoxified bisulfite-pretreated corncob.

Pretreatment and saccharification of corn cobs using partially purified fungal ligninozymes

AbstractCorn cobs consist primarily of a lignocellulosic material comprising hemicellulose, cellulose, and lignin in a crystalline state, which is resistant to microbial saccharification. Bioethanol production from corn cobs has rarely been attempted, especially using chemical pretreatment methods.The present study deals with the production and purification of fungal (Phanerochaete chrysosporium MTCC 787 and Pleurotus florida PAU 22‐01) extracellular ligninolytic enzymes – lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac) – followed by their utilization for the biological pretreatment of corn cobs along with saccharification using commercial cellulase. Crude LiP, MnP, and Lac demonstrated specific activity of 2.23, 2.1, and 2.63 U/mg, respectively.The one‐step purification of crude enzyme using diethyl amino ethyl (DEAE) cellulose ion exchange chromatography resulted in 11.3, 10.1 and 8.62‐fold purification of LiP, MnP and Lac activity, respectively, with corresponding specific activity of 25.1 U/mg (LiP), 21.2 U/mg (MnP) and 22.7 U/mg (Lac) in the partially purified ligninozymes. Using the latter, biological pretreatment of 2.5 g corn cobs in a reaction volume of 30 mL containing approximately 200 units of Lac, Lip and MnP enzymes (in phosphate buffer, pH 6) resulted in a maximum of 78.4% delignification with a saccharification efficiency of 97.1% using commercial cellulases.

Bimolecular optimization of cellulase production by <i>Richoderma citrinoviride</i> and <i>Aspergillus niger</i> isolates on corn cob, rice bran and sorghum bran as biomass substrates

This work focuses on the assessment of the conditions relevant for the improvement of enzymes hydrolysis of pretreated corn cob, rice bran and sorghum bran by using Trichoderma Citrinoviride and Aspergillus niger. To achieve this, different fermentation conditions were applied to assess their effect in the optimization of cellulase production. Effects of fermentation duration, inoculation size, temperature and pH of fermentation on cellulase production were investigated. At 96 hrs of fermentation, maxim cellusale product was found to be at optimum in both organisms. Hence, 6% substrates concentration with 10 discs of 8mm inoculum size yielded maximum cellulase production in both A. niger and T. citrinoviride after 5 days of incubation. At 35ºC, A niger and T citrinoviride recorded maximum cellulase production 0.50 mg/ml in sorghum bran while 40ºC was optimum for maximum cellulase production for T, citrinoviride on corn cob. Whereas, pH 5.0 T. citrinoviride exhibits maximum cellulase production with sorghum bran 1.30 mg/ml compared to carboxymetyyl cellulose which served as control and sorghum bran 1.2mg/ml. These results highlight the potentials of T. citrinoviride as species of fungus for the industrial production of cellulase using Agricultural wastes as substrates. Cellulase yield was repressed in the presence of glucose and was induced in the presence of corn cob, rice bran and sorghum using T. citrinoviride. Cellulase yield from Corn cob, rice bran and sorghum bran differed significantly at (P<0.05) from glucose.

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Thermal behavior and production distributions of organosolv-phase oxidization pretreatment of biomass coupled with fast pyrolysis

Organosolv-phase oxidization pretreatment of corncob (OOPC) at ambient pressure and temperature coupled with fast pyrolysis was first performed. The effects of organosolv/water phase with/without oxidation, Fe2+ contents, H2O2 concentrations, pyrolytic behavior, and kinetic analysis on the distributions of pyrolytic products were investigated. The yields of higher oxygen-containing components such as anhydrosugars were obtained from fast pyrolysis of OOPC in comparison with raw, organosolv-phase, and water-phase oxidization pretreated corncobs. With the increase Fe2+ contents and H2O2 concentrations during organosolv-phase oxidization pretreatment, the O/C ratios (0.35–0.51), levoglucosan yield (2.2–160.2 mg/g), and relative content of anhydrosugars (5.5–72.9 %) were remarkably improved whereas the yield of pyrolytic chars (21.4–13.4 %) and average E values (65.5–50.4 kJ/mol) significantly decreased compared to raw sample. The pyrolysis products of OOPC were remarkably transformed from low-molecular compounds of raw sample to high-molecular compounds. The higher Fe2+ contents and H2O2 concentrations were conductive to the elimination of biomass resistant and the formation of oxygen-rich fractions mainly consisting of considerable amounts of C–O, O–CO, and –OH bonds due to the effective removal of carbon-rich fractions (C–C bonds), which were responsible for the increase in anhydrosugars.

Enzymatic hydrolysis of organosolv-pretreated corncob and succinic acid production by Actinobacillus succinogenes

In this study, the conversion of organosolv-treated corncob into monosaccharides through enzymatic saccharification was investigated, with the resulting monosaccharides being utilized as a carbon source to produce succinic acid. The synergy between the cellulase and xylanase provided 76% cellulose and 64% xylan digestibility at 50 °C and pH 5.2. In separate hydrolysis and fermentation (SHF), Actinobacillus succinogenes produced 12.7 g/L of succinic acid from the hydrolysate with 0.12 g/g yield based on the pretreated corncob. Simultaneous saccharification and fermentation (SSF) demonstrated better performance with 16 g/L succinic acid titer and 0.24 g/g yield, though SHF provided a higher production rate. The condition in the SSF (37 °C and pH near neutral) was suboptimal for the enzymes, thus the succinic acid production was limited by the saccharification step. These findings emphasize the potential of organosolv-treated corncob to serve as an enzymatic hydrolysis substrate without neutralization and detoxification, supplying glucose and xylose for succinic acid production by A. succinogenes.

Statistical Optimization of Tween-80-Assisted Potassium Hydroxide Pretreatment and Enzymatic Hydrolysis for Enhancing Sugar Yields from Corn Cob

With the addition of Tween 80, potassium hydroxide pretreatment and enzymatic hydrolysis were statistically optimized to maximize sugar yields from corn cob (CC). The results indicated that the sugar yields from CC could be influenced significantly by the potassium hydroxide concentration, temperature and time during pretreatment. The optimized pretreatment conditions were as follows: potassium hydroxide, 46 g·L−1; Tween 80, 3.0 g·L−1; solid dose, 200 g·L−1; temperature, 78 °C; and time, 50 min. After optimization, the lignin reduction and recoveries of cellulose and hemicellulose were 89.7%, 97.8% and 68.0%, respectively. In addition, sugar production could also be influenced by the biomass loading, enzyme loading and reaction time. A maximal glucose production (518.48 mg·gds−1, milligrams per gram of dry substrate) and xylose production (351.14 mg·gds−1), 97.2% cellulose conversion and 82.9% hemicellulose conversion from CC could be obtained when the biomass loading was 195 g·L−1 and the enzyme loading was 8.9 FPU·gds−1 (filter paper activity units per gram of dry substrate) and when the Tween 80 concentration was 3.0 g·L−1 at 50 °C for 30.4 h during hydrolysis. This is the first systematic study of combined Tween 80 pretreatment of CC by potassium hydroxide and hydrolysis of CC by cellulase preparation to increase sugar production.

Effect of alkaline and steam pre-treatment on saccharification of corn cob and production of cellullase from fungal consortium

Lignocellulosic biomass as fossil fuel alternative comes with its challenges such as its inherent stability and recalcitrance. The use of commercial cellulase in the removal of lignin comes with high cost. This research seeks to answer questions on how alkaline and steam pre-treatment improve cellulose/glucose liberation from lignocellulosic biomass (corn cobs) using a consortium of <i>pichia kudriavzevii</i> and <i>cyberlindnera fabianii.</i><br /> In the current study, the effectiveness of steam and sodium hydroxide (NaOH) pre-treatment for reducing corn cob structure was examined, and the pre-treated biomass afterwards was exposed to the hydrolyzing activity of a consortium enzyme cocktail that was custom-formulated. The results of an analysis of composition showed that while alkaline pre-treated corn cob (APC) had 1.2% lignin, 75.8% cellulose, and 10.9% hemicellulose, steam pre-treated corn cob (SPC) had 2.5% lignin, 67.2% cellulose, and 25% hemicellulose. Lignin was eliminated from the biomass of corn cobs using both steam and NaOH pre-treatment. The hydrolyzing effect of the holocellulolytic enzyme cocktail, prepared with two multifunctional enzymes, was applied to the alkaline and steam pre-treated samples. This hydrolyzed SPCs more effectively than APC feedstocks, revealing that steam was a more effective pre-treatment attaining a remarkable 8.33 U/mg endoglucanase, 5.56 U/mg exoglycanase and 8.97U/mg beta-glucosidase levels (event 1) and glucose peak concentration of 0.433 mol/mL at 48 hours (event 2); according to a thorough examination of cellulase capacity and glucose levels.<br /> Overall, the consortium enzyme cocktail effectively hydrolyzed agricultural feedstocks that had undergone alkaline pre-treatment, making it a desirable option for usage in the bioconversion procedure in the biorefinery sector. This study demonstrates an effective technique for turning agricultural waste (corn cob) into high-value products through effective and practical chemical pre-processing.

Addressing two major limitations in high-solids enzymatic hydrolysis by an ordered polyethylene glycol pre-incubated strategy: Rheological properties and lignin adsorption for enzyme

High-solids enzymatic hydrolysis for biomass has currently received considerable interest. However, the solid effect during the process limits its economic feasibility. This work presented an ordered polyethylene glycol (PEG) pre-incubated strategy for enhancing the auxiliary effect of PEG in a high-solids enzymatic hydrolysis system. The substrate and enzyme were separately pre-incubated with PEG in this strategy. The ordered PEG pre-incubated strategies yielded a maximum glucose concentration of 166.6 g/L from 32 % (w/v) pretreated corncob with an enzymatic yield of 94.1 % by 72 h hydrolysis. Using this method, PEG not only lessened the lignin adsorption to cellulase but also altered particle rheological characteristics in the high-solids enzymatic hydrolysis system as a viscosity modifier. This study offered a new insight into the mechanism behind the PEG synergistic effect and would make it possible to achieve efficient high-solids loading hydrolysis in the commercial manufacture of cellulosic ethanol.

Effect of deep eutectic solvent pretreatment on biohydrogen production from corncob: pretreatment temperature and duration

ABSTRACTDeep eutectic solvent pretreatment with different temperatures and durations was applied to corncob to increase hydrogen yield via photo-fermentation. The correlation of composition, enzymatic hydrolysis, and hydrogen production in pretreated corncobs, as well as energy conversion was evaluated. Deep eutectic solvent pretreatment effectively dissolved lignin, retained cellulose, and enhanced both enzymatic hydrolysis and hydrogen production. The maximum cumulative hydrogen yield obtained under a pretreatment condition of 50°C and 12 h was 677.45 mL; this was 2.72 times higher than that of untreated corncob, and the corresponding lignin removal and enzymatic reduction of sugar concentration were 79.15% and 49.83 g/L, respectively; the highest energy conversion efficiency was 12.08%. The hydrogen production delay period was shortened, and the maximum shortening time was 18.9 h. Moreover, the cellulose content in pretreated corncob was positively correlated with both reducing sugar concentration and hydrogen yield and had the strongest influence on hydrogen production.

Chemical pretreatment of corncob for the selective dissolution of hemicellulose and lignin: influence of pretreatment on the chemical, morphological and thermal features

The aim of this work was to remove the hemicellulose and lignin fraction from corncob using chemical pretreatments, and to stablish the effect of that on the composition, microstructure, and thermal properties of corncob. The biomass was pretreated with H2SO4 and NaOH solution to dissolve hemicellulose and lignin portion. Likewise, the biomass pretreated was characterized by scanning electron microscope, IR spectroscopy and TGA methods. It was found that the acid pretreatment disrupt the hemicellulose structure by hydrolysis of glycoside bonds. Moreover, the corncob morphology becomes flaky after acid pretreatment due to dissolution of hemicellulose. The lignin is removed during alkaline pretreatment by solvation of aryl groups. In addition, the crystalline morphology of cellulose fibers was disrupted, increasing the surface area. The pretreatment of corncob with 1.0% H2SO4 and 0.1 M NaOH solubilized ∼42.6% and ∼20.9% of the biomass, respectively. The soluble products were analyzed by FTIR, Fehling test, and calorimetric analysis, to stablish their composition and heat content. The hydrolysis of hemicellulose leads to the release of the monomeric sugars and soluble oligomers. Moreover, the lignin of corncob releases more energy per unit of mass, making it an energy-denser component of corncob.

Using deep eutectic solvents to pretreat corncob for the fabrication of sustainable lignocellulose hydrogels

Using agricultural wastes as raw materials to manufacture high value-added materials with green and economical processes is of great significance. In this study, corncob processed by deep eutectic solvents (DESs) pretreatment (80–130 °C) can be successfully prepared into lignocellulose-based hydrogels (LCHs) by a facile and green ZnCl2/CaCl2 solvent system. An appropriate amount of lignin can be well dispersed and filled in the structure of LCHs, thus improving the mechanical properties of the hydrogel. The hydrogel using 120 °C pretreated corncob as starting material reached the best tensile stress (144.4 kPa) and compressive stress (401.4 kPa). Due to the excellent flexibility and the presence of a large number of metal ions, the hydrogels prepared from the 120 °C pretreated corncob were assembled into a capacitor and got an energy density of 110.2 Wh/kg at the power density of 495.0 W/kg. In short, this study provides a simple and green method to prepare LCHs and a novel efficient utilization route of the corncob.

A novel sucrose-inducible expression system and its application for production of biomass-degrading enzymes in Aspergillus niger

BackgroundFilamentous fungi are extensively exploited as important enzyme producers due to the superior secretory capability. However, the complexity of their secretomes greatly impairs the titer and purity of heterologous enzymes. Meanwhile, high-efficient evaluation and production of bulk enzymes, such as biomass-degrading enzymes, necessitate constructing powerful expression systems for bio-refinery applications.ResultsA novel sucrose-inducible expression system based on the host strain Aspergillus niger ATCC 20611 and the β-fructofuranosidase promoter (PfopA) was constructed. A. niger ATCC 20611 preferentially utilized sucrose for rapid growth and β-fructofuranosidase production. Its secretory background was relatively clean because β-fructofuranosidase, the key enzyme responsible for sucrose utilization, was essentially not secreted into the medium and the extracellular protease activity was low. Furthermore, the PfopA promoter showed a sucrose concentration-dependent induction pattern and was not subject to glucose repression. Moreover, the strength of PfopA was 7.68-fold higher than that of the commonly used glyceraldehyde-3-phosphate dehydrogenase promoter (PgpdA) with enhanced green fluorescence protein (EGFP) as a reporter. Thus, A. niger ATCC 20611 coupled with the PfopA promoter was used as an expression system to express a β-glucosidase gene (bgla) from A. niger C112, allowing the production of β-glucosidase at a titer of 17.84 U/mL. The crude β-glucosidase preparation could remarkably improve glucose yield in the saccharification of pretreated corncob residues when added to the cellulase mixture of Trichoderma reesei QM9414. The efficacy of this expression system was further demonstrated by co-expressing the T. reesei-derived chitinase Chi46 and β-N-acetylglucosaminidase Nag1 to obtain an efficient chitin-degrading enzyme cocktail, which could achieve the production of N-acetyl-D-glucosamine from colloidal chitin with a conversion ratio of 91.83%. Besides, the purity of the above-secreted biomass-degrading enzymes in the crude culture supernatant was over 86%.ConclusionsThis PfopA-driven expression system expands the genetic toolbox of A. niger and broadens the application field of the traditional fructo-oligosaccharides-producing strain A. niger ATCC 20611, advancing it to become a high-performing enzyme-producing cell factory. In particular, the sucrose-inducible expression system possessed the capacity to produce biomass-degrading enzymes at a high level and evade endogenous protein interference, providing a potential purification-free enzyme production platform for bio-refinery applications.

Big data mining, rational modification, and ancestral sequence reconstruction inferred multiple xylose isomerases for biorefinery.

The isomerization of xylose to xylulose is considered the most promising approach to initiate xylose bioconversion. Here, phylogeny-guided big data mining, rational modification, and ancestral sequence reconstruction strategies were implemented to explore new active xylose isomerases (XIs) for Saccharomyces cerevisiae. Significantly, 13 new active XIs for S. cerevisiae were mined or artificially created. Moreover, the importance of the amino-terminal fragment for maintaining basic XI activity was demonstrated. With the mined XIs, four efficient xylose-utilizing S. cerevisiae were constructed and evolved, among which the strain S. cerevisiae CRD5HS contributed to ethanol titers as high as 85.95 and 94.76 g/liter from pretreated corn stover and corn cob, respectively, without detoxifying or washing pretreated biomass. Potential genetic targets obtained from adaptive laboratory evolution were further analyzed by sequencing the high-performance strains. The combined XI mining methods described here provide practical references for mining other scarce and valuable enzymes.

Effectiveness of ruminal xylanase with an extra proline-rich C-terminus on lignocellulosic biomass degradation

The efficient degradation of plant polysaccharides in agricultural waste requires xylanases with high catalytic activity. In this study, the C-terminal proline-rich GH10 xylanase XynA from sheep rumen was investigated using product analysis, structural characterization, truncated and site-directed mutagenesis, molecular dynamics simulation, and application evaluation, revealing that the proline-rich C-terminus contributes to the interaction at the substrate-binding pocket to reduce the binding free energy. Compared to the C-terminally truncated enzyme XynA-Tr, XynA has a more favorable conformation for proton transfer and affinity attack, facilitating the degradation of oligomeric and beechwood xylan without altering the hydrolysis pattern. Moreover, both the reduced sugar yield and weight loss of the pretreated wheat bran, corn cob, and corn stalk hydrolyzed by XynA for 12 h increased by more than 30 %. These findings are important to better understand the relationship between enzyme activities and their terminal regions and suggest candidate materials for lignocellulosic biomass utilization.

Isolation of Lactococcus sp. X1 from Termite Gut, and Its Application in Lactic Acid Production

The production of lactic acid (LA) from lignocellulosic biomass is an important route for the exploitation of renewable resources; nevertheless, effective LA production from this feedstock is challenged by several limitations, such as pentose and oligosaccharide utilization. In this study, a new strain, Lactococcus sp. X1, which is capable of fermenting glucose, xylose, and several disaccharides to produce L-lactic acid, was isolated from the gut of a wood-feeding termite, Coptotermes formosanus. Compared to conventional lactic acid bacteria, Lactococcus sp. X1 requires less complex nitrogen sources, which might in turn reduce the cost of LA production. In addition, Lactococcus sp. X1 was able to completely ferment 50 g/L of glucose within 3 days, giving a high LA yield of 99.9%, and its LA yield from 50 g/L of pretreated corncob reached up to 0.34 g/g substrates in the presence of a commercial cellulase. Strain X1 was also capable of excreting two kinds of nutritional factors, namely biotin and vitamin C, indicating its crucial role in the nourishment of the termite. In conclusion, Lactococcus sp. X1 is a new lactic acid bacterium, which may hold promise for application in cost-effective LA production as well as in the field of food additives.

Organosolv pretreatment of corncob for enzymatic hydrolysis of Xylan

Organosolv pretreatment of corncob for enzymatic hydrolysis of Xylan