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Economically feasible ethanol production requires efficient hydrolysis of lignocellulosic biomass and high–temperature processing to enable simultaneous saccharification and fermentation. During the lignocellulolysic hydrolysate, the yeast must encounter with a multiple of inhibitors such as heat and furfural. To solve this problem, a potential fermentative yeast strain that tolerated simultaneous multistress and enhance ethanol concentration was investigated. Twenty yeast isolates were classified into two major yeast species, namely Pichia kudriavzevii (twelve isolates) and Candida tropicalis (eight isolates). All P. kudriavzevii isolates were able to grow at high temperature (45 °C) and exhibited stress tolerance toward furfural. Among P. kudriavzevii isolates, NUCG–S3 presented the highest specific growth rate under each stress condition of heat and furfural, and multistress. Morphological changes in P. kudriavzevii isolates (NUCG–S2, NUCG–S3, NUKL–P1, NUKL–P3, and NUOR–J1) showed alteration in mean cell length and width compared to the non–stress condition. Ethanol production by glucose was also determined. The yeast strain, NUCG–S3, gave the highest ethanol concentrations at 99.46 ± 0.82, 62.23 ± 0.96, and 65.80 ± 0.62 g/l (P < 0.05) under temperature of 30 °C, 40 °C, and 42 °C, respectively. The tolerant isolated yeast NUCG–S3 achieved ethanol production of 53.58 ± 3.36 and 48.06 ± 3.31 g/l (P < 0.05) in the presence of 15 mM furfural and multistress (42 °C with 15 mM furfural), respectively. Based on the results of the present study, the novel thermos and furfural-tolerant yeast strain P. kudriavzevii NUCG–S3 showed promise as a highly proficient yeast for high–temperature ethanol fermentation. [ABSTRACT FROM AUTHOR]

Background: The use of ionic liquids (ILs) to fractionate lignocelluloses for various bio-based chemicals productions is in the ascendant. On this basis, the protic ILs consisting of triethylammonium hydrogen sulfate ([TEA][HSO4]) possessed great promise due to the low price, low pollution, and high efficiency. In this study, the microwave-assistant [TEA][HSO4] fractionation process was established for corn stover fractionation, so as to facilitate the monomeric sugars production and supported the downstream acetone–butanol–ethanol (ABE) fermentation. Results: The assistance of microwave irradiation could obviously shorten the fractionation period of corn stover. Under the optimized condition (190 W for 3 min), high xylan removal (93.17 ± 0.63%) and delignification rate (72.90 ± 0.81%) were realized. The mechanisms for the promotion effect of the microwave to the protic ILs fractionation process were ascribed to the synergistic effect of the IL and microwaves to the depolymerization of lignocellulose through the ionic conduction, which can be clarified by the characterization of the pulps and the isolated lignin specimens. Downstream valorization of the fractionated pulps into ABE productions was also investigated. The [TEA][HSO4] free corn stover hydrolysate was capable of producing 12.58 g L−1 of ABE from overall 38.20 g L−1 of monomeric sugars without detoxification and additional nutrients supplementation. Conclusions: The assistance of microwave irradiation could significantly promote the corn stover fractionation by [TEA][HSO4]. Mass balance indicated that 8.1 g of ABE and 16.61 g of technical lignin can be generated from 100 g of raw corn stover based on the novel fractionation strategy. [ABSTRACT FROM AUTHOR]

Despite the significant progress in the research, the problem of finding an efficient method for producing bioethanol from renewable lignocellulosic waste materials remains unresolved. Our investigation aimed to assess the efficacy of ethanol production from sugar beet pulp (SBP) utilising various approaches, including pretreatment variations, enzymatic processes, and microbial hydrolysis. Our research involved using the post-cultivation concentrate of T. viride LOCK 0588 grown in the SBP-based medium as a source of enzymes. The SBP hydrolysis process was carried out for 48 h at 50 °C. The quantity of sugar released, up to 61 g dm−3, through the utilisation of this extract proved to be on par with the outcomes achieved by the application of the commercial Cellic Ctec2 preparation. The final yields of the ethanol production with the use of the coculture of S. cerevisiae (Ethanol Red) and Scheffersomyces stipitis LOCK 0047 strain were in the range 5.1 ± 0.11 kg 100 kg−1 ÷ 5.38 ± 0.11 kg 100 kg−1. These results provide a solid basis for improving larger-scale industrial procedures that involve converting SBP into bioethanol using a cost-efficient approach of microbial hydrolysis with T. viride and a blend of pentose and hexose fermenting yeast. [ABSTRACT FROM AUTHOR]

The unwashed alkali-treated lignocellulose can be directly enzymatically hydrolyzed and fermented via pH adjustment with acids. The use of acids would give a burden on production cost. Furfural residue (FR) which is the acidic solid waste from lignocellulose-derived furfural production process was employed in this study as a pH regulator. The corn cob-derived FR was used to adjust the pH value of alkali-treated corn stover (PCS) to 4.8 for enzymatic hydrolysis and ethanol fermentation. The unwashed PCS adjusted by FR got higher enzymatic hydrolysis efficiency (EHE) than the washed PCS samples. Meanwhile, the mixing of PCS and FR had a synergistic effect on the EHE of PCS. The fermentation of enzymatic hydrolysate from unwashed PCS-FR mixture at 20% solid concentration could attain ethanol production of 26.54 ± 0.02 mg/mL with a yield of 89.53 ± 0.08%. This work created a novel recycling way of FR as a pH regulator for improving the bioconversion of alkali-treated lignocellulose. It also provided a novel clue for the valuable valorization of wastes from corn production. [ABSTRACT FROM AUTHOR]

Agricultural residues are more suitable for biochemical conversion to produce bulk commodities preferentially through anaerobic fermentation with less energy consumption and lower contamination risk. Steam explosion is applicable for industrial production, and biological pretreatment is not suitable for fermentation under pure culture conditions due to its slow rate and contamination risk. Cellulases produced in situ and formulated with glucosidases are cost-effective for building up sugar platforms through simultaneous saccharification and co-fermentation (SSCF) and separate hydrolysis and co-fermentation (SHCF) to produce volatile and nonvolatile products, respectively. In situ utilization of CO 2 can credit cellulosic ethanol, and both yield and titer must be improved substantially for butanol to be produced as an advanced biofuel, but microbial lipids produced aerobically with intensive energy consumption and low yield cannot be affordable as feedstock for biodiesel production. Lignocellulose is an alternative to fossil resources, but its biochemical conversion is not economically competitive. While decentralized processing can reduce logistical cost for this feedstock, sugar platforms need to be developed with energy-saving pretreatment technologies and cost-effective cellulases, and products must be selected correctly. Anaerobic fermentation with less energy consumption and lower contamination risk is preferred, particularly for producing biofuels. Great effort has been devoted to producing cellulosic ethanol, but CO 2 released with large quantities during ethanol fermentation must be utilized in situ for credit. Unless titer and yield are improved substantially, butanol cannot be produced as an advanced biofuel. Microbial lipids produced through aerobic fermentation with low yield and intensive energy consumption are not affordable as feedstocks for biodiesel production. [ABSTRACT FROM AUTHOR]

The iron ion-catalyzed hydrogen peroxide pretreatment (Fe-HP pretreatment) can be used as a green pretreatment way for promoting bio-refining of corncob and bio-jet fuel production. [Display omitted] • An environmentally friendly Fe-HP biomass pretreatment was developed. • Fe-HP pretreatment significantly improved bio-jet fuel production. • The existence and role of ROS in the Fe-HP pretreatment process was confirmed. • Dual functional catalyst improved the selectivity of bio-jet fuels. • High ethanol conversion (95.9 %) with a 70.9 % jet-fuel selectivity was obtained. Developing efficient and green pretreatment pathways is of great significance for the production of biofuels. The purpose of this work is to evaluate that iron-ion catalyzed hydrogen peroxide (Fe-HP) pretreatment can be used for the enhancement of bio-jet fuel production using corncob as a typical lignocellulosic biomass. Typically, the Fe-HP pretreatment was conducted under the following pretreatment conditions: H 2 O 2 concentration of 5.0 wt%, iron ion concentration of 400 ppm, biomass loading of 10 wt%, 70 °C and 60 min. The Fe-HP pretreated corncob shows a high sugar yield of 39.2 % (w/w) under the optimal enzymolysis conditions (50 ℃, pH 4.8, 72 h). Ethanol yield of 35.2 % (w/w) was obtained under the optimal fermentation conditions (30 ℃, pH 5.5, 72 h). Especially, the directional transformation of corncob to bio-jet fuels was achieved by integrating biomass fermentation and catalytic synthesis. High ethanol conversion of 95.9C-mol % and good jet fuel selectivity of 70.9C-mol % were obtained by using the bi-functional catalyst (HSAPO-34/NiHβ) under the optimal synthesis conditions (200 °C, 5 MPa, 3 h). Based on the biomass characterization and reactive oxygen specie's analysis, the possible role and mechanism of the iron-ion catalyzed hydrogen peroxide pretreatment was addressed. The iron ion catalyst can accelerate the decomposition of hydrogen peroxide to form hydroxyl radicals, and thus promoting biomass depolymerization and lignin removal from lignocellulose. The pretreatment increased sugar yield and concentration during enzymatic hydrolysis, which indirectly enhanced ethanol fermentation and bio-jet fuel production. [ABSTRACT FROM AUTHOR]

As the main by-product of apple processing, apple pomace should be fully utilized, which was crucial for the quality and efficiency improvement of the whole apple industry. Based on the established subcritical water extraction in the previous study, the apple pomace pectin was successfully extracted in a green and efficient way, which also produced solid residue called de-pectin apple pomace needed to be furtherly utilized. For its main component was lignocellulose, the de-pectin apple pomace was suitable to be transformed to bioethanol. However, the direct ethanol conversion rate of de-pectin apple pomace was low, so the high-efficiency ethanol conversion process was established by optimizing the parameters of pretreatment and enzymatic hydrolysis in the present study. The optimal pretreatment parameters were 180°C (pretreatment temperature), 10 min (pretreatment time), and 1:40 (solid-liquid ratio, g/mL). With the optimal enzyme usage of cellulase (CEL-01) of 5 FPU/g (32.17 mg/g) and β-glucosidase (SPE-007AL) of 1 U/g (34.94 μL/g), the ethanol concentrations of SHF(Separate hydrolysis and fermentation) and SSSF(Semi simultaneous saccharification and fermentation) were 42.48 g/L and 42.50 g/L on a substrate loading of 23% (w/v) and which about Fed-SHF(Fed-batch separate hydrolysis and fermentation) and Fed-SSSF(Fed-batch semi simultaneous saccharification and fermentation) were 57.90 g/L and 66.40 g/L on a substrate loading of 35% (w/v), indicating that de-pectin apple pomace had the excellent potential for industrial ethanol conversion. In addition, for there were some functional components in the residues from transformation process, such as polyphenol and lignin, the pretreatment liquid was fermented by Lactobacillus to develop a functional beverages, which possessed excellent antioxidant activity (more than 90% scavenging activity of DPPH) and more than 108 CFU/mL of viable counts, while solid residues obtained after ethanol fermentation were used to produce chewable tablets for the high content of lignin, which possessed well binding ability of chenodeoxycholic acid of 15 mg/g. Based on the double subcritical water pretreatment, the whole components utilization system of the apple pomace was established. Meanwhile, the mass balance based on 1 kg apple pomace utilization was also analyzed to indicate the detailed substrate transformation process of the whole components utilization system, which was beneficial to resolving the problem of apple pomace utilization in a more feasible way. [Display omitted] • The bioethanol production from apple pomace was efficiently improved by subcritical water pretreatment. • Ethanol concentration reached to 66.40 g/L in Fed-Batch SSSF based on substrate loading of 35% (w/v). • Whole components utilization of de-pectin apple pomace had been realized. • Mass balance of the whole components utilization system had been analyzed. [ABSTRACT FROM AUTHOR]

Effective pretreatment is essential for successfully utilizing renewable resources such as lignocellulosic biomass in the production of bioethanol. In this study, ternary deep eutectic solvents (DESs), namely choline chloride/lactic acid/glycerol (ChCl/LA/Gly), choline chloride/oxalic acid/glycerol (ChCl/OA/Gly), choline chloride/lactic acid/ethylene glycol (ChCl/LA/EG), and choline chloride/oxalic acid/ethylene glycol (ChCl/OA/EG) were prepared and employed for the pretreatment of cellulose-rich Napier grass (NG). Post treatment, the NG hydrolysate was subjected to enzymatic saccharification followed by ethanol fermentation. The results showed effective delignification of NG after treatment with the prepared ternary DESs, with ChCl/LA/EG removing a maximum of 92.89% lignin. The efficiency of the prepared DESs is attributed to their low densities, pH, and viscosity. Enzymatic saccharification of ChCl/LA/EG-treated NG resulted in a 1.68 fold increase in reducing sugar yield compared to that of untreated NG. All pretreated NG produced more bioethanol via a separate hydrolysis and fermentation (SHF) process than untreated NG after Saccharomyces cerevisiae fermentation. A maximum of 0.37 g bioethanol/g of biomass was obtained from the one-pot process using ChCl/LA/Gly pretreatment. FTIR and XRD analyses of untreated and pretreated NG corroborated the efficacy of the ternary DESs on cellulose recovery and delignification. Also, enzymatic and microbial inhibition studies on the prepared DESs show their potential to be employed in a one-pot process for biorefinery. The results of the present investigation show the potential of utilizing eco-friendly DESs and renewable resources for the production of bioethanol, a viable option to fossil fuels. [ABSTRACT FROM AUTHOR]

Addressing the high cost of comprehensive utilization of lignocellulose, an efficient and green lignocellulosic biorefinery process was developed in this study, which can achieve the co-production of lignin, sugar and lipid. A series of FDES were prepared using glycerin, choline chloride (ChCl), and H 2 SO 4 for the pretreatment of lignocellulose and ultimately for fermentation. After optimization, the hemicellulose removal reaches 98 %, and enzymatic hydrolysis rate of pretreated solids exceeds 90 %. The FDES was then recovered and reused for pretreatment, in total five batches of lignocellulose were pretreated, only a slight decrease in lignin and hemicellulose removal rate occurred, no significant decrease in lignin yield, and a decrease in solid enzyme hydrolysis from 83.26 % to 78.25 %. Finally, FDES after using five batches was used as a substrate for Rhodotorula glutinis with biomass up to 40.25 g/L and lipid concentration up to 8.33 g/L. In addition, the cellulose was probed with high solid-loading enzymatic hydrolysis, obtaining high concentration of glucose (137.4 g/L) for ethanol fermentation. In conclusion, this study developed a biorefinery technology for the efficient utilization of lignocellulosic fractions and pretreatment solvents, which reduces the cost of DES pretreatments of lignocellulose, and achieves the cogeneration of lignin, sugar and lipids. [Display omitted] [ABSTRACT FROM AUTHOR]

Pretreatment of lignocellulosic biomass by breaking down its complex structure is an essential step to facilitate enzymatic hydrolysis of lignocellulose and subsequent bioethanol fermentation. Herein, an eco-friendly pretreatment strategy was developed by applying deep eutectic solvent (DES) cocktail. Attributing to the synergistic effect of two DESs (e.g., betaine-glycerol and choline chloride-oxalic acid (or choline chloride-acetamide)), an impressive 89.51% digestibility for glucan and 75.43% for xylan were achieved. Characterization of pretreated corn stover showed that DES cocktail changed substrate surface structure and enlarged structure pores, which could improve the accessibility of cellulase. The pretreated corn stover was also employed in ethanol fermentation and achieved the yield of 73.35%. Recycling experiments demonstrated the potential reusability of DES cocktail in a sustainable manner towards various biomass sources. These findings highlight the effectiveness and versatility of the developed DES cocktail pretreatment method, paving the way for sustainable bioethanol production from lignocellulosic feedstocks. [Display omitted] • Betaine-glycerol based DES cocktail was developed for corn stover pretreatment. • DES cocktail pretreatment increased glucan recovery up to 13.1% compared to single DES pretreatment. • The saccharification rate of enzyme-digested glucose after optimization of pretreatment temperature was as high as 89.51%. • Ethanol yield reached 73.61% with a maximum increase of 10.16% after DES cocktail pretreatment. • DES cocktails maintained ∼83% pretreatment effect after four recovery cycles. [ABSTRACT FROM AUTHOR]

Several lignocellulosic wastes are generated in the pulp and paper industry (PPI), such as small wood chips (pinchips) and paper sludge, presenting a high cellulose content suitable to be converted into biofuels or bio-products in a forest biorefinery scheme. In this work, two schemes of biorefinery were proposed for their valorization, processing small eucalyptus wood pinchips in two different strategies: (i) autohydrolysis at 230ºC, and (ii) autohydrolysis at 195ºC followed by organosolv process (47.7% ethanol-water, 198ºC for 60 min). More than 95% of cellulose was recovered in both schemes. In the combined process, 76% of delignification was achieved and 78% of xylan was solubilized as xylooligosaccharides. To reduce operational cost of lignocellulosic biomass-to-ethanol fermentation, the mixture of the treated eucalyptus pinchips from two processes with sludge was also proposed to increase the initial glucan content and to supply a rich source of nitrogen (present in the sludge). For that, two experimental designs were carried out for ethanol production by simultaneous saccharification and fermentation (SSF) process. Ethanol from SSF assays using sludge as co-substrate at 0.6 g of sludge/g of treated wood pinchips and 16 FPU/g of pretreated solids allowed to obtain 59 g/L (90% of conversion) and 46 g/L (96% of conversion) when blended with the wood from autohydrolysis and with the wood from autohydrolysis followed by organosolv, respectively. Overall, this study shows an alternative process valorization of biomasses derived from PPI for production of advanced biofuels and bio-products (such as xylooligosaccharides and lignin) contributing to achieving a circular economy. • Multi-waste valorization approach was proposed to produce biofuel and bioproducts. • Autohydrolysis and organosolv processes allowed > 90% glucan recoveries. • Higher than 40 g/L of ethanol and 90% of yield were obtained in both schemes developed. • Blending with sludge improve ethanol production from pretreated eucalyptus wood. [ABSTRACT FROM AUTHOR]

• Upgrading DAP by post-hydrolysis for carbon efficient conversion of lignocellulose. • A radar chart method was used for the comprehensive evaluation of DAP performance. • One-pot post-hydrolysis and SSF without detoxification and sterilization. • Preserved 45.2 % of original β-O-4 linkages in fractionated lignin. • 66 % of lignocellulose carbon was recovered as ethanol, xylose and reactive lignin. Dry acid pretreatment (DAP) as a promising process for industrial biorefinery provide an efficient bioconversion of cellulose without free wastewater, although the partial xylan and lignin degrade to inhibitors or recondense. A biorefinery strategy for carbon efficient conversion of lignocellulose into bioethanol, xylose, and reactive lignin was developed by upgrading DAP with post-hydrolysis. The results showed that lignocellulose after mild DAP (175 °C, acid dosage of 15 mg/g dry material) obtained higher xylan recovery and lower inhibitors than that of general DAP. Subsequently, post-hydrolysis, simultaneous saccharification and ethanol fermentation were performed at solids loading of 20 wt% without detoxification and sterilization, resulting in xylose and ethanol yield of 71.8 % and 67.6 %. The fractionated lignin presented more reactive β-aryl ether linkages and less condensation than that from DAP. 66 % of lignocellulose carbon was recovered as ethanol, xylose and reactive lignin. This upgrading biorefinery strategy provided an easy-to-operate process for integrated utilization of lignocellulose. [ABSTRACT FROM AUTHOR]