Bioconversion Of Cellulose Research Articles

Evaluation and characterization of the cellulolytic bacterium, Bacillus pumilus SL8 isolated from the gut of oriental leafworm Spodoptera litura: An assessment of its potential value for lignocellulose bioconversion

Continuous and increasing demands for bioenergy have prompted the discovery of novel routes for effective bioconversion of lignocellulose into commodity chemicals. To this end, cellulolytic bacteria were isolated and screened from the gut system of oriental leafworm, Spodoptera litura. The plate-based screening revealed maximum cellulolytic activities by Bacillus pumilus SL8 displaying a clearance zone of 21 mm with a hydrolytic capacity of 10.5. When tested further, B. pumilus SL8 depicted the highest substrate degradation of corn cob powder (CCP, 59.2%) followed by sawdust (SD, 54.2%), and sugarcane bagasse (SCB, 52.6%). Among the cellulolytic enzymes, maximum activities were achieved for xylanase, endoglucanase, and β-glucosidase that corresponded to 50.5 ± 5, 22.8 ± 2.4, and 22.4 ± 3 IUmg−1 protein, respectively on the wheat husk, CMC, and Avicel. The field emission scanning electron microscopy (FESEM) revealed adhesion of the bacteria to the substrate causing structural alterations due to hydrolysis. The hydrolysis of the substrate was further substantiated through FTIR analysis that depicted reduction in the intensity of cellulose representing bands such as 662, 895, 1184, 1371, and 1599 to 1749 cm−1 signifying degradation by B. pumilus SL8. Additionally, B. pumilus SL8 demonstrated its coculturing efficiency with the yeast strain for bioconversion of cellulose into bioethanol. The overall results suggest the potential utility of B. pumilus SL8 for biotechnological applications.

Effect of cellulose crystallinity modification by starch gel treatment for improvement in ethanol fermentation rate by non-GM yeast cell factories

This paper studies the reduction of crystallinity degree (CD) of cellulose treated with starch gel (SG), and the correlation of CD with the fermentation efficiency of cellulose to fuel-grade ethanol. Cellulose bioconversion from wood sawdust, consisting of three processes, was conducted in the same batch (one-step). The XRD and TEM analysis revealed 11% reduction in cellulose CD after its treatment with SG. One-step bioconversion process was performed employing two cell factories (CF) of non-engineered S. cerevisiae. CFs contained non- engineered S. cerevisiae cells covered with either SG entrapping Trichoderma reesei or cellulases prepared in the laboratory and immobilized in SG. The consolidated fermentation of treated cellulose resulted in an increase of bioethanol concentration (60-90%) in 2-day fermentation and the maximum ethanol concentration reached was approximately 5mL/L (3.95g/L). The fermentation efficiency for grade-fuel ethanol production was improved by cellulose pretreatment using SG to achieve reduced CD.

Unraveling aerobic cultivable cellulolytic microorganisms within the gastrointestinal tract of sheep (Ovis aries) and their evaluation for cellulose biodegradation.

Anaerobic cellulolytic microbes in the gastrointestinal tract (GT) of ruminants have been well-documented; however, knowledge of aerobic microbes with cellulolytic activities in the ruminant GT is comparably limited. Here, we unraveled aerobic cultivable cellulolytic microbes in the GT of Ujimqin sheep (Ovis aries) and evaluated the cellulolytic potential of the promising isolates. Twenty-two strains were found to possess cellulose-degrading potential by Congo-red staining and phylogenetic analysis of the 16S rDNA/ITS sequence revealed that all strains belonged to nine genera, i.e., Bacillus, Streptomyces, Pseudomonas, Lactobacillus, Brachybacterium, Sanguibacter, Rhizobium, Fusarium, and Aspergillus. Strains with high cellulolytic activity were selected to further evaluate the activities of various enzymes in lignocellulosic alfalfa hay (Medicago sativa). Among them, isolate Bacillus subtilis RE2510 showed the highest potential for cellulose degradation, considering the high endoglucanase (0.1478 ± 0.0014 IU mL-1), exoglucanase (0.1735 ± 0.0012 IU mL-1), and β-glucosidase (0.3817 ± 0.0031 IU mL-1) after 10-day incubation with alfalfa hay. A significant destruction effect of the cellulose structure and the attachment of B. subtilis RE2510 to the hay were also revealed using a scanning electron microscope. This study expands our knowledge of aerobic cellulolytic isolates from the GT of sheep and highlights their potential application as a microbial additive in the aerobic process of cellulose bioconversion.

Evaluating the mechanism of milk protein as an efficient lignin blocker for boosting the enzymatic hydrolysis of lignocellulosic substrates

The residual lignin in pretreated biomass significantly hinders the bio-conversion of cellulose into monosaccharides.

Biosynthesis of fuel-grade ethanol from cellobiose by a cell-factory of non-GMO Saccharomyces cerevisiae/starch-gel-cellulase

The aim of this work was to ferment cellobiose to fuel-grade ethanol in one-step bioconversion employing a cell-factory (CF) of non-Genetically Modified Organism (non-GMO) Saccharomyces cerevisiae. The proposed technology involved the production of a freeze-dried preparation of CF of non-GMO S. cerevisiae covered by a layer of starch-gel (SG) containing cellulase enzyme. Parameters studied for one-step bioconversion of cellobiose to ethanol included temperature (33–40 °C), cellobiose concentration (70–150 g/L), and cellulase activity (60–150 FPU/g). High conversion (90%) of cellobiose in a 48 h one-step process was achieved using 70 g/L cellobiose, 150 FPU/g at 30 °C, indicating the efficiency of CF. S. cerevisiae in CF were also capable to ferment at 40 °C with the major role of enzyme activity and cellobiose concentration in fermentation. In our studies, the ethanol yield and conversion of cellobiose were found competitive, with other processes reported with S. cerevisiae as GMO and enzyme co-immobilized in alginates beads. Consequently, the results revealed a new concept for bio-ethanol production from cellobiose in one-step simultaneous-hydrolysis-fermentation (OSHF), which could be a precursor study for large-scale cellulose bioconversion for fuel-grade alcohol production.

Ultrafast fractionation of wild-type and CSE down-regulated poplars by microwave-assisted deep eutectic solvents (DES) for cellulose bioconversion enhancement and lignin nanoparticles fabrication

Genetic engineering is considered a promising approach to decrease “biomass recalcitrance” and enhance the lignin valorization. Caffeoyl Shikimate Esterase (CSE) was recently indicated to play an important role in lignin biosynthesis. However, the effect of this enzyme on poplar lignin structure and subsequent treatment has not been systematically analyzed. In this study, ultrafast microwave-assisted deep eutectic solvents (DES) pretreatment was effectively performed to deconstruct the main components in wild-type (WT) and CSE down-regulated poplar. After pretreatment with two kinds of DES (ethylene glycol-based and glycerol-based DES), the saccharification efficiency of CSE down-regulated poplar was significantly improved, reaching 96.15%. In addition, the yield of DES lignin increased to 62.66% and 72.89% after Ethylene Glycol and Glycerol-based DES pretreatment in CSE poplar woods as compared to WT poplar wood (48.06% and 60.47%). Moreover, structural and morphological variations of lignin after CSE down-regulation and DES pretreatments have been systematically studied by 2D-HSQC, 31P NMR, GPC, SEM, and TEM techniques. Results showed that native lignin from WT and CSE down-regulated poplars had similar structural features excepted for high content of H-type and p-hydroxybenzoate (PB) units in the CSE down-regulated poplar lignin. Furthermore, quantification of different linkages (β-O-4, β-β, β-5, etc.) in native lignin and DES lignin fractions suggested the ultrafast DES fractionation resulted in the significant cleavage of these linkages under glycerol-based DES pretreatment. Meanwhile, the DES lignin from glycerol-based DES pretreatment was found to be small and homogeneous lignin nanoparticles (LNPs). In short, the glycerol-based DES pretreatment is an environmentally benign scheme to produce easily digestible biomass and the LNPs with narrow size distribution. These findings are very important in assessing the fabricability of CSE poplar in the current biorefinery scenario.

Cellulose Degrading Ability of Bacterial Strains Isolated from Gut of Termites in Vinhlong Province - Vietnam

Cellulose are the most abundant renewable biomass. The bioconversion of cellulose plays an important role for sustainable development and application in alcohol production, compost production and waste treatment. Termites were known as the most successful wood-degrading species on the earth, can degrade in large quantities of cellulosic biomass by activities of enzymes secreted by the termites and/or their gut. A total of 70 bacterial isolates were isolated from the gut of termites obtained from thirteen termite nests in TraOn district, VinhLong province, Mekong Delta, Vietnam. Of the 70 bacterial isolates, 60 (86%) are able to degrade CMC (Carboxyl Methyl Cellulose) after culturing in media containing CMC agar and halo formation after staining with Congo red. Among of them, 5 isolates having high CMC degradation efficiency are chosen to evaluate the potential ability to liberate glucose from cellulose of straw for 5, 10, 15 and 20 days respectively at room temperatures. The results showed that all of the 5 isolates have the cellulose degradation ability and produce the highest glucose contents after 15 days. Out of the 5 isolates, 2 produced glucose in large quantities are 2T1 isolate (0.73 g/L) and 5T6 isolate (0.79 g/L) in hydrolysis solutions. The 2T1, 5T6 strains were 98.99%, 99.01% of identity Paenibacillus humicus strain T20C, Psychrobacter faecalis strain AP3Ka respectively by 16S rRNA genes sequencing and could be potential sources of enzymes for cellulose hydrolysis from cellulosic biomass in future.

Physicochemical Variation of the Main Components during Wild Pretreatment Process Based on the Concept of the Whole Utilization of Bamboo

Attempting to correlate the characteristics of the fractionated components from bamboo to its susceptibility to enzyme is often inconclusive depending on the parameters of pretreatment conditions. Based on the integrated analysis of chemical components, cellulose bioconversion, characteristic property of isolated hemicellulose, and lignin, the optimal mild pretreatment operation for Moso bamboo was 4% NaOH in 20% ethanol aqueous solution. A total of 91.9% mass was successfully recovered, and 66% bioconversion efficiency of the cellulosic sample was finally achieved. Meanwhile, over 25% hemicelluloses and 7% lignin were isolated, and the characteristic analysis indicated that the fractionated biomacromolecule maintained the original core structure, which is a benefit to be further utilized for the production of chemicals or polymers.

Enhancement of the enzymatic hydrolysis efficiency of wheat bran using the Bacillus strains and their consortium

In the downstream process, the bioconversion of lignocellulosic biomass can be improved by applying a biological pretreatment procedure using microorganisms to produce hydrolytic enzymes to modify the recalcitrant structure of lignocellulose. In this study, various Bacillus strains (B. subtilis B.01162 and B.01212, B. coagulans B.01123 and B.01139, B. cereus B.00076 and B.01718, B. licheniformis B.01223 and B.01231) were evaluated for the degrading capacity of wheat bran in the submerged medium using enzymatic activities, reducing sugars and weight loss as indicators. The obtained results revealed that the B. subtilis B.01162, B. coagulans B.01123 and B. cereus B.00076 could be promising degraders for the wheat bran pretreatment. Besides, the application of their consortium (the combination of 2–3 Bacillus species) showed the positive effects on cellulose bioconversion compared with monocultures. Among them, the mixture of B. subtilis B.01162 and B. coagulans B.01123 increased significantly the cellulase, endo-glucanase, and xylanase enzyme activity resulting in accelerating the lignocellulose degradation. Our results served a very good base for the development of microbial consortium for biological pretreatment of lignocellulosic raw materials.

Short-time deep eutectic solvents pretreatment enhanced production of fermentable sugars and tailored lignin nanoparticles from abaca

Deep eutectic solvents (DES) pretreatment is a promising approach to decrease “biomass recalcitrance” and boost the cellulose bioconversion as well as lignin valorization. In this study, a short-time DES pretreatment strategy was performed to enhance the production of high-yield fermentable sugars and tailored lignin nanoparticles (LNPs) from abaca. The glucose yield reached 92.4% under the optimal pretreatment condition (110 °C, 30 min), which was dramatically increased in comparison with that (9.5%) of control abaca. Simultaneously, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) techniques indicated that the removed and regenerated DES lignin fractions displayed depolymerized structures and have relatively low molecular weight with relatively homogeneous morphology and narrow size distribution. Transmission electron microscope (TEM) analysis indicated that these lignin fractions are LNPs and the size of the optimal LNPs fraction is ranged from 30 nm to 50 nm. Moreover, all the DES lignin exhibited excellent antioxidant activities as compared to the commercial antioxidant butylated hydroxytoluene (BHT), which can be used as a promising natural antioxidant in industry. In short, this study demonstrated that the short-time DES pretreatment will improve the enzymatic digestibility and facilitate the controllable production and valorization of LNPs from abaca biomass, which will further promote the economic and overall benefits of biorefinery.

Bioethanol Production of Cellulase Producing Bacteria from Soils of Agrowaste Field

With decades of studies on cellulose bioconversion, cellulases have been playing an important role in producing fermentable sugars from lignocellulosic biomass. Copious microorganisms that are able to degrade cellulose have been isolated and identified. The present study has been undertaken to isolate and screen the cellulase producing bacteria from soils of agrowaste field. Cellulase production has been qualitatively analyzed in carboxy methylcellulose (CMC) agar medium after congo red staining and NaCl treatment by interpretation with zones around the potent colonies. Out of the seven isolates, only two showed cellulase production. The morphogical and molecular characterization revealed its identity as Escherichia coli and Staphylococcus aureus. The potential of organisms for bioethanol production has been investigated using two substrates, namely, paper and leaves by subjecting with a pre-treatment process using acid hydrolysis to remove lignin which acts as physical barrier to cellulolytic enzymes. Ethanolic fermentation was done using Saccharomyces cerevisiae for 24-48 h and then the bioethanol produced was qualitatively proved by iodoform assay. These finding proves that ethanol can be made from the agricultural waste and the process is recommended as a means of generating wealth from waste.

Bioethanol production from Jatropha seed cake via dilute acid hydrolysis and fermentation by Saccharomyces cerevisiae

The interest in using Jatropha curcas L. as a feedstock for the production of bio-diesel is rapidly growing. Available literatures holds [promise for the simultaneous wasteland reclamation capability and oil yields of the plant hence fueling the Jatropha bio-ethanol hopes. This research investigated the bioconversion of cellulose from press cakes of Jatropha oil seeds, which is a byproduct from a biodiesel plant, into ethanol by using the methods of acid pretreatment, hydrolysis and fermentation by Saccharomyces cerevisiae. The process includes the pretreatment method of the finely ground cellulosic solid oilseed cake with dilute sulphuric acid and heating the mixture at a high temperature to break the crystalline structure of the lignocellulose to facilitate the hydrolysis of cellulosic component by dilute acids. About 63.33% ethanol was recovered as confirmed by the infra-red spectroscopy and the investigated physicochemical parameters show that the produced bioethanol holds promise for its use as a possible candidate for replacement for petroleum diesel.

A novel cellulolytic system from Aspergillus flavipes for lignocellulosic bio-conversion

Background/Objectives: The importance of enzymatic bioconversion of cellulose cannot be understated and enzyme systems which complement existing enzymes, with broad ranges of pH and temperatures and hydrolyze cellulose synergistically with other enzymes are required for bioconversions. The study was undertaken to isolate and characterize cellulolytic organisms. Methodology: Isolation of cellulolytic strains from soil samples with degrading cellulosic wastes, screening and species level identification of Fungal strain was conducted. Stability of the enzyme systems over different pH and temperature and purification study of enzymes were carried out. Results: Fungal isolate, which exhibited 0.08 IU of filter paper (FP) activity, 0.33 IU of Carboxy methyl cellulose (CMC) activity and 15IU of xylanase activity was selected and identified as Aspergillus flavipes. Purification by ion exchange chromatography and gel filtration chromatography yielded a typical endoglucanase, a fraction showing activity with both avicel and caboxy mthyl cellulase(CMC) and a third fraction against CMC and avicel. GPC of third fraction showed that the enzymes had cross reactivity to the substrates used. Conclusion: Our study proved that Aspergillus flavipes is capable of degrading lignocellulose and its FP activity and CMC activity was higher than other isolates and was comparable to enzymes of a standard strain T. koninjii. To our knowledge this study is the first detailed report of a system of cellulases, suitable for saccharification of lignocellulosic biomass alone or synergistically with other enzymes produced by Aspergillus flavipes. Keywords: Filter paper activity; CMC; glucosidase; endoglucanase; pNPG; lignocellulosic b saccharification

Enzymatic response of ryegrass cellulose and hemicellulose valorization introduced by sequential alkaline extractions

BackgroundIn view of the natural resistance of hemicelluloses in lignocellulosic biomass on bioconversion of cellulose into fermentable sugars, alkali extraction is considered as an effective method for gradually fractionating hemicelluloses and increasing the bioconversion efficiency of cellulose. In the present study, sequential alkaline extractions were performed on the delignified ryegrass material to achieve high bioconversion efficiency of cellulose and comprehensively investigated the structural features of hemicellulosic fractions for further applications.ResultsSequential alkaline extractions removed hemicelluloses from cellulose-rich substrates and degraded part of amorphous cellulose, reducing yields of cellulose-rich substrates from 73.0 to 27.7% and increasing crystallinity indexes from 31.7 to 41.0%. Alkaline extraction enhanced bioconversion of cellulose by removal of hemicelluloses and swelling of cellulose, increasing of enzymatic hydrolysis from 72.3 to 95.3%. In addition, alkaline extraction gradually fractionated hemicelluloses into six fractions, containing arabinoxylans as the main polysaccharides and part of β-glucans. Simultaneously, increasing of alkaline concentration degraded hemicellulosic polysaccharides, which resulted in a decreasing their molecular weights from 67,510 to 50,720 g/mol.ConclusionsThe present study demonstrated that the sequential alkaline extraction conditions had significant effects on the enzymatic hydrolysis efficiency of cellulose and the investigation of the physicochemical properties of hemicellulose. Overall, the investigation the enzymatic hydrolysis efficiency of cellulose-rich substrates and the structural features of hemicelluloses from ryegrass will provide useful information for the efficient utilization of cellulose and hemicelluloses in biorefineries.

Microwave-assisted deep eutectic solvents (DES) pretreatment of control and transgenic poplars for boosting the lignin valorization and cellulose bioconversion

Reducing the “biomass recalcitrance” and simultaneously improving the efficiency of deconstruction and conversion is vitally important in a biorefinery process. Herein, a microwave-assisted deep eutectic solvents (DES) pretreatment was developed to deconstruct the control and transgenic (C3H, HCT and C3H + HCT co-inhibition) poplars, and improve the lignin extractability and valorization. NMR and GPC results showed that native lignin (Double Enzymatic Lignin, DEL) in different poplars exhibited slightly different structural characteristics, affecting the subsequent lignin extractability and value-added applications. After two kinds of DES (ethylene glycol-based and glycerol-based DES) pretreatments, the yield of DES lignin was obviously increased to 45.38–53.09 % and 46.38–54.30 % in transgenic poplar woods as compared to control poplar wood (37.25 and 38.86 %). In addition, molecular weight, and abundances of different linkages (β-O-4, β-β, β-5, etc.) in the DES lignin fractions were significantly decreased, suggesting the microwave-assisted DES pretreatment has a strong deconstruction ability towards to poplar wood. Moreover, the rapid and efficient pretreatment facilitated the isolation of the lignin fractions from transgenic poplars, and the regenerated DES lignin fractions exhibited excellent antioxidant properties, which will lay the foundation for the lignin valorization. Furthermore, the enzymatic saccharification ratios of the DES pretreated substrates were significantly increased to 87.36–96.55 % in control and transgenic poplar woods, indicating that microwave-assisted DES pretreatment indeed boosted cellulose bioconversion. In short, the combination of genetic modification and DES pretreatment can significantly reduce the “biomass recalcitrance” and promote the biomass valorization.

Structural aspects of β-glucosidase of Myceliophthora thermophila (MtBgl3c) by homology modelling and molecular docking

Cellulases are the enzymes with diverse range of industrial applications. Cellulases degrade cellulose into monomeric glucose units by hydrolysing β-1,4-glycosidic bonds. There are three components of cellulases: a) endoglucanase, b) exoglucanase and c) β-glucosidase which act synergistically in cellulose bioconversion. The cellulases are the third largest industrial enzymes with a great potential in bioethanol production. In this investigation, a β-glucosidase of a thermophilic fungus Myceliophthora thermophila (MtBgl3c) was analysed for its structural characterization using in silico approaches. The protein structure of MtBgl3c is unknown, therefore an attempt has been made to model 3D structure using Modeller 9.23 software. The MtBgl3c protein model generated was validated from Verify 3D and ERRAT scores of 89.37% and 71.25%, respectively derived from SAVES. Using RAMPAGE the Ramachandran plot was generated, which predicted the accuracy of the 3D model with 91.5% amino acid residues in the favored region. The ion binding and N-glycosylation sites were also predicted. The generated model was docked with cellobiose to predict the most favorable binding sites of MtBgl3c. The key amino acid residues involved in cellobiose bonding are Val88, Asp106, Asp287, Tyr255, Arg170, Glu514. The catalytic conserved amino residues of MtBgl3c were identified. The dock score of cellobiose with MtBgl3c is much lower (–6.46 kcal/mol) than that of glucose (–5.61 kcal/mol), suggesting its high affinity for cellobiose. The docking data of MtBgl3c with glucose illustrate its tolerance to glucose. The present study provides insight into structural characteristics of the MtBgl3c which can be further validated by experimental data. Highlights 3D structure of β-glucosidase (MtBgl3c) of Myceliophthora thermophila is being proposed based on computational analyses The amino acid residues Asp106, Asp287, Tyr255, Arg170 and Glu514 have been identified to play catalytically important role in substrate binding Docking and interaction of MtBgl3c with cellobiose and glucose has been confirmed Docking analysis of MtBgl3c with glucose suggested its glucose tolerance The data would be useful in engineering enzymes for attaining higher catalytic efficiency Communicated by Ramaswamy H. Sarma

Supplementation of O2-containing gas nanobubble water to enhance methane production from anaerobic digestion of cellulose

Nanobubble water (NBW) contains 106–108 gas bubbles per milliliter with diameter <1 µm. These fine bubbles possess high mass transfer efficiency and hydrophobic property beneficial for agricultural and biomedical application. Nowadays, much attention has been paid to the secure and sustainable management of lignocellulosic wastes. Cellulose is regarded as one kind of slowly biodegradable organic components owing to its complex crystalline structure. This study investigated the effect of O2-containing gas NBW on anaerobic digestion (AD) of cellulose for methane production. Results show that the cumulative methane yields from the reactors with Air-NBW (193 NmL/g-VSreduced), N2-NBW (196 NmL/g-VSreduced) and O2-NBW (233 NmL/g-VSreduced) addition were increased by 8–30% in comparison to the control (with the same amount of deionized water addition) (179 NmL/g-VSreduced). Under NBW addition, the reductions in cellulose content and cellulose crystallinity were respectively enhanced by 8–14% and 9–21% during AD, in which cellulase activity was elevated by 10–38%. The O2-NBW reactor was found to have the highest electron transport system activity, increasing by 1.7 times compared to the control, most probably due to the collapse of O2-nanobubbles and release of O2 resulting in micro-oxygen environment under the test condition. Besides, microbial community analysis suggests that the direct interspecies electron transfer could be quickly established with the addition of NBW. Results from this study also shed light on the mechanisms involved in the bioconversion of cellulose to methane via AD supplemented with NBW.

Precise promoter integration improves cellulose bioconversion and thermotolerance in Clostridium cellulolyticum

Lignocellulose has been used for production of sustainable biofuels and value-added chemicals. However, the low-efficiency bioconversion of lignocellulose greatly contributes to a high production cost. Here, we employed CRISPR-Cas9 editing to improve cellulose degradation efficiency by editing a regulatory element of the cip-cel gene cluster in Clostridium cellulolyticum. Insertion of a synthetic promoter (P4) and an endogenous promoter (P2) in the mspI-deficient parental strain (Δ2866) created chromosomal integrants, P4-2866 and P2-2866, respectively. Both engineered strains increased the transcript abundance of downstream polycistronic genes and enhanced in vitro cellulolytic activities of isolated cellulosomes. A high cellulose load of 20 g/L suppressed cellulose degradation in the parental strain in the first 150 h fermentation; whereas P4-2866 and P2-2866 hydrolyzed 29% and 53% of the cellulose, respectively. Both engineered strains also demonstrated a greater growth rate and a higher cell biomass yield. Interestingly, the Δ2866 parental strain demonstrated better thermotolerance than the wildtype strain, and promoter insertion further enhanced thermotolerance. Similar improvements in cell growth and cellulose degradation were reproduced by promoter insertion in the wildtype strain and a lactate production-defective mutant (LM). P2 insertion in LM increased ethanol titer by 65%. Together, the editing of regulatory elements of catabolic gene clusters provides new perspectives on improving cellulose bioconversion in microbes.

Synergistic benefits from a lignin-first biorefinery of poplar via coupling acesulfamate ionic liquid followed by mild alkaline extraction

A novel mind-set, termed lignin-first biorefinery, is bewitching to synchronously boost lignin output for entirely lignocellulosic utilization. A lignin-first fractionation, using a food-additive derived ionic liquid (1-ethyl-3-methylimidazolium acesulfamate, emimAce) and mild alkaline pretreatments, was formed for the purposely isolating poplar lignin, whilst delivering a cellulose-rich substrate that can be easily available for enzymatic digestion. The emimAce-driven lignin, alkali-soluble lignin and hemicellulose, and accessible cellulose were sequentially gained. We introduce a lignin-first approach to extract the amorphous fractions, destroy the robust architecture, and reform cellulose-I to II, thereby advancing the cellulose bioconversion from 15.4 to 90.5%. A harvest of 70.7% lignin, 52.1% hemicellulose, and 330.1 mg/g glucose was fulfilled from raw poplar. A structural ‘‘beginning-to-end’’ analysis of lignin inferred that emimAce ions are expected to interact with lignin β-aryl-ether due to their aromatic character. It was reasonable to derive benefits from lignin-first technique that can substantially augment the domain of biorefinering.

Enhanced production of cellulosic butanol by simultaneous co-saccharification and fermentation of water-soluble cellulose oligomers obtained by chemical hydrolysis

Butanol attracted interests as a drop-in biofuel obtainable from cellulosic wastes. However, the process typically used for cellulose bioconversion, i.e., separate hydrolysis and fermentation (SHF) of pretreated cellulose (Process I), is insufficient for energy-efficient production of fuel grade butanol due to the limited obtainable butanol titer. Recently, post-hydrolysis of chemically formed water-soluble cellulose oligomers was suggested for acetone-butanol-ethanol (ABE) production in SHF mode of operation (Process II). In this study, it was found that simultaneous saccharification and fermentation of the soluble oligomers (oligomeric-SSF) (Process III) and simultaneous co-saccharification and fermentation (SCSF) of soluble oligomers along with regenerated cellulose (Process IV) are promising alternatives for upgrading the titer and yield of cellulosic butanol production by Clostridium acetobutylicum. In Process III, utilizing the oligomeric hydrolysate obtained through dilute acid hydrolysis at 120 °C for 60 min using 1% acid through oligomeric-SSF led to 14.2 g/L ABE production, i.e., 65% higher than Process I. In addition, using the oligomeric hydrolysate in SCSF resulted in 24 g/L ABE (16 g/L butanol) production with an overall yield of 182 g ABE/kg cellulose. Process IV showed 191% higher titer and 14% higher yield of ABE production, compared with Process I.