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Integrating plant cell wall engineering and process consolidation using biocompatible deep eutectic solvents could enable the development of sustainable biorefineries that effectively utilize both carbohydrates and lignin.

Microplastics (MPs) are contaminants of emerging concern that accumulate in various environments, where they pose threats to both the ecosystem and public health. Since MPs have been detected in drinking water resources and wastewater effluents, more efficient treatment is needed at wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). This review discusses the potential of biological, photochemical, Fenton (-like) systems, ozonation, and other oxidation processes in the treatment of MPs in terms of their indicators of oxidation such as mass loss and surface oxidation. The oxidation processes were further analyzed in terms of limitations and environmental implications. Most previous studies examining MPs degradation using conventional treatments-such as UV disinfection, ozonation, and chlorination-employed significantly higher doses than the common doses applied in DWTPs and WWTPs. Owing to such dose gaps, the oxidative transformation of MPs observed in many previous studies are not likely to occur under practical conditions. Some novel oxidation processes showed promising MPs treatment efficiencies, while many of them have not yet been applied on a larger scale due to high costs and the lack of extensive basic research. Health and environmental impacts related to the discharge of oxidized MPs in effluents should be considered carefully in different aspects: the role as vectors of external pollutants, release of organic compounds (including organic byproducts from oxidation) and fragmentation into smaller particles as MPs circulate in the ecosystem as well as the possibility of bioaccumulation. Future research should also focus on ways to incorporate developed oxidation processes in DWTPs and WWTPs to mitigate MPs contamination.

Efficient xylose catabolism in engineered

This study achieved high production of hexanol via gas fermentation using Clostridium carboxidivorans P7 by extracting hexanol from the fermentation broth. The hexanol extraction efficiency and inhibitory effects on C. carboxidivorans P7 of 2-butyl-1-octanol, hexyl hexanoate and oleyl alcohol were examined, and oleyl alcohol was selected as the extraction solvent. Oleyl alcohol was added at the beginning of fermentation and during fermentation or a small volume of oleyl alcohol was repeatedly added during fermentation. The addition of a small volume of oleyl alcohol during fermentation was the most effective for CO consumption and hexanol production (5.06 g/L), yielding the highest known hexanol titer through any type of fermentation including gas fermentation. Hexanol production was further enhanced to 8.45 g/L with the repeated addition of oleyl alcohol and ethanol during gas fermentation. The results of this study will enable sustainable and carbon-neutral hexanol production via gas fermentation.

Efficient xylose catabolism in engineered Saccharomyces cerevisiae enables more economical lignocellulosic biorefinery with improved production yields per unit of biomass. Yet, the product profile of glucose/xylose co-fermenting S. cerevisiae is mainly limited to bioethanol and a few other chemicals. Here, we introduced an n-butanol-biosynthesis pathway into a glucose/xylose co-fermenting S. cerevisiae strain (XUSEA) to evaluate its potential on the production of acetyl-CoA derived products. Higher n-butanol production of glucose/xylose co-fermenting strain was explained by the transcriptomic landscape, which revealed strongly increased acetyl-CoA and NADPH pools when compared to a glucose fermenting wild-type strain. The acetate supplementation expected to support acetyl-CoA pool further increased n-butanol production, which was also validated during the fermentation of lignocellulosic hydrolysates containing acetate. Our findings imply the feasibility of lignocellulosic biorefinery for producing fuels and chemicals derived from a key intermediate of acetyl-CoA through glucose/xylose co-fermentation.

Herein, it was unearthed that manganese peroxidase (MnP) from Phanerochaete chrysosporium, a lignin-degrading enzyme, is capable of not only directly decomposing cellulosic components but also boosting cellulase activity. MnP decomposes various cellulosic substrates (carboxymethyl cellulose, cellobiose [CMC], and Avicel®) and produces reducing sugars rather than oxidized sugars such as lactone and ketoaldolase. MnP with MnII in acetate buffer evolves the MnIII-acetate complex functioning as a strong oxidant, and the non-specificity of MnIII-acetate enables cellulose-decomposition. The catalytic mechanism was proposed by analyzing catalytic products derived from MnP-treated cellopentaose. Notably, MnP also boosts cellulase activity on CMC and Avicel®, even considering the cellulolytic activity of MnP itself. To the best of the authors’ knowledge, this is the first report demonstrating a previously unknown fungal MnP activity in cellulose-decomposition in addition to a known delignification activity. Consequently, the results provide a promising insight for further investigation of the versatility of lignin-degrading biocatalysts.

Lignocellulosic biomass has considerable potential for the production of fuels and chemicals as a promising alternative to conventional fossil fuels. However, the bioconversion of lignocellulosic biomass to desired products must be improved to reach economic viability. One of the main technical hurdles is the presence of inhibitors in biomass hydrolysates, which hampers the bioconversion efficiency by biorefinery microbial platforms such as Saccharomyces cerevisiae in terms of both production yields and rates. In particular, acetic acid, a major inhibitor derived from lignocellulosic biomass, severely restrains the performance of engineered xylose‐utilizing S. cerevisiae strains, resulting in decreased cell growth, xylose utilization rate, and product yield. In this study, the robustness of XUSE, one of the best xylose‐utilizing strains, was improved for the efficient conversion of lignocellulosic biomass into bioethanol under the inhibitory condition of acetic acid stress. Through adaptive laboratory evolution, we successfully developed the evolved strain XUSAE57, which efficiently converted xylose to ethanol with high yields of 0.43–0.50 g ethanol/g xylose even under 2–5 g/L of acetic stress. XUSAE57 not only achieved twofold higher ethanol yields but also improved the xylose utilization rate by more than twofold compared to those of XUSE in the presence of 4 g/L of acetic acid. During fermentation of lignocellulosic hydrolysate, XUSAE57 simultaneously converted glucose and xylose with the highest ethanol yield reported to date (0.49 g ethanol/g sugars). This study demonstrates that the bioconversion of lignocellulosic biomass by an engineered strain could be significantly improved through adaptive laboratory evolution for acetate tolerance, which could help realize the development of an economically feasible lignocellulosic biorefinery to produce fuels and chemicals.

Butyric acid-producing strain Clostridium tyrobutyricum ATCC25755 produces acetic acid as a byproduct, which lowers butyric acid yield and selectivity. Supplementing glycerol would be a rational approach to enhance a NADH-requiring metabolite butyric acid selectivity by increasing NADH availability; however, there has been no report butyric acid production using glycerol as either a sole carbon source or a co-substrate with C. tyrobutyricum. In this study, glycerol was supplemented along with sugar to increase NADH availability facilitating the production of butyric acid. C. tyrobutyricum was found to simultaneously consume glucose and glycerol only when acetic acid was present. Notably, acetic acid was not produced but consumed. The amount of glycerol consumption was linearly dependent on the amount of acetic acid consumption. When mixed sugars (glucose 80 g/L and xylose 30 g/L) and crude glycerol were used, not only exogenous acetic acid consumption but also acetic acid reassimilation were clearly observed, resulting in significantly enhanced butyric acid production (54.79 g/L), yield (0.464 g/g), and selectivity (98.3%) compared to sugar-only fermentation (production, 35.42 g/L; yield, 0.339 g/g; selectivity, 69.1%). Therefore, this study would pave the way for selective and cost-effective butyric acid production using sugars and glycerol from biodiesel facility.

Several bioprocessing technologies, such as separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and consolidated bioprocessing (CBP), have been highlighted to produce bio-based fuels and chemicals from lignocellulosic biomass. Successful CBP, an efficient and economical lignocellulosic biorefinery process compared with other processes, requires microorganisms with sufficient cellulolytic activity and biofuel/chemical-producing ability. Here, we report the complete genome of Paenibacillus sp. CAA11, a newly isolated promising microbial host for CBP-producing ethanol and organic acids from cellulose. The genome of Paenibacillus sp. CAA11 comprises one 4,888,410 bp chromosome with a G + C content of 48.68% containing 4418 protein-coding genes, 102 tRNA genes, and 39 rRNA genes. The functionally active cellulase, encoded by CAA_GH5 was identified to belong to glycosyl hydrolase family 5 (GH5) and consisted of a catalytic domain and a cellulose-binding domain 3 (CBM3). When cellulolytic activity of CAA_GH5 was assayed through Congo red method by measuring the size of halo zone, the recombinant Bacillus subtilis RIK1285 expressing CAA_GH5 showed a comparable cellulolytic activity to B. subtilis RIK1285 expressing Cel5, a previously verified powerful bacterial cellulase. This study demonstrates the potential of Paenibacillus sp. CAA11 as a CBP-enabling microbe for cost-effective biofuels/chemicals production from lignocellulosic biomass.

Background Engineered strains of Saccharomyces cerevisiae have significantly improved the prospects of biorefinery by improving the bioconversion yields in lignocellulosic bioethanol production and expanding the product profiles to include advanced biofuels and chemicals. However, the lignocellulosic biorefinery concept has not been fully applied using engineered strains in which either xylose utilization or advanced biofuel/chemical production pathways have been upgraded separately. Specifically, high-performance xylose-fermenting strains have rarely been employed as advanced biofuel and chemical production platforms and require further engineering to expand their product profiles. Results In this study, we refactored a high-performance xylose-fermenting S. cerevisiae that could potentially serve as a platform strain for advanced biofuels and biochemical production. Through combinatorial CRISPR–Cas9-mediated rational and evolutionary engineering, we obtained a newly refactored isomerase-based xylose-fermenting strain, XUSE, that demonstrated efficient conversion of xylose into ethanol with a high yield of 0.43 g/g. In addition, XUSE exhibited the simultaneous fermentation of glucose and xylose with negligible glucose inhibition, indicating the potential of this isomerase-based xylose-utilizing strain for lignocellulosic biorefinery. The genomic and transcriptomic analysis of XUSE revealed beneficial mutations and changes in gene expression that are responsible for the enhanced xylose fermentation performance of XUSE. Conclusions In this study, we developed a high-performance xylose-fermenting S. cerevisiae strain, XUSE, with high ethanol yield and negligible glucose inhibition. Understanding the genomic and transcriptomic characteristics of XUSE revealed isomerase-based engineering strategies for improved xylose fermentation in S. cerevisiae. With high xylose fermentation performance and room for further engineering, XUSE could serve as a promising platform strain for lignocellulosic biorefinery.

Technologies for degradation of three major components of lignocellulose (e.g. cellulose, hemicellulose and lignin) are needed to efficiently utilize lignocellulose. Here, we report Bacillus sp. 275 isolated from a mudflat exhibiting various lignocellulolytic activities including cellulase, xylanase, laccase and peroxidase in the cell culture supernatant. The complete genome of Bacillus sp. 275 strain contains 3832 protein cording sequences and an average G+C content of 46.32% on one chromosome (4045,581bp) and one plasmid (6389bp). The genes encoding enzymes related to the degradation of cellulose, xylan and lignin were detected in the Bacillus sp. 275 genome. In addition, the genes encoding glucosidases that hydrolyze starch, mannan, galactoside and arabinan were also found in the genome, implying that Bacillus sp. 275 has potentially a wide range of uses in the degradation of polysaccharide in lignocellulosic biomasses.

Additional file 5: Table S1. Strains and plasmids used in this study.

Background Lignocellulosic biorefinery offers economical and sustainable production of fuels and chemicals. Saccharomyces cerevisiae, a promising industrial host for biorefinery, has been intensively developed to expand its product profile. However, the sequential and slow conversion of xylose into target products remains one of the main challenges for realizing efficient industrial lignocellulosic biorefinery. Results In this study, we developed a powerful mixed-sugar co-fermenting strain of S. cerevisiae, XUSEA, with improved xylose conversion capacity during simultaneous glucose/xylose co-fermentation. To reinforce xylose catabolism, the overexpression target in the pentose phosphate pathway was selected using a DNA assembler method and overexpressed increasing xylose consumption and ethanol production by twofold. The performance of the newly engineered strain with improved xylose catabolism was further boosted by elevating fermentation temperature and thus significantly reduced the co-fermentation time by half. Through combined efforts of reinforcing the pathway of xylose catabolism and elevating the fermentation temperature, XUSEA achieved simultaneous co-fermentation of lignocellulosic hydrolysates, composed of 39.6 g L−1 glucose and 23.1 g L−1 xylose, within 24 h producing 30.1 g L−1 ethanol with a yield of 0.48 g g−1. Conclusions Owing to its superior co-fermentation performance and ability for further engineering, XUSEA has potential as a platform in a lignocellulosic biorefinery toward realizing a more economical and sustainable process for large-scale bioethanol production.

A Gram-negative, catalase-positive, mesophilic, obligately aerobic bacterium designated JRM2-1T was isolated from forest soil of Jirisan Mountain, Republic of Korea, and its taxonomic position was investigated based on a polyphasic taxonomic approach. Cells of strain JRM2-1T grew optimally at pH 5.0–7.0 and at 25 °C. Strain JRM2-1T was susceptible to chloramphenicol, gentamicin, kanamycin, nalidixic acid, rifampicin, streptomycin and tetracycline. On the basis of 16S rRNA gene sequence similarity, the closest neighbour of strain JRM2-1T was Burkholderia rhizosphaerae WR43T (98.1 %). On the basis of our phylogenetic analysis, strain JRM2-1T is clearly distinguished from related species of the genus Burkholderia and is clustered with plant-associated members of the genus. The major cellular fatty acids were C16 : 0, C17 : 0 cyclo and C19 : 0 cyclo ω8c. The polar lipid profile of strain JRM2-1T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, several unidentified aminolipids and an unidentified aminophospholipid. The isoprenoid quinone of strain JRM2-1T was Q-8 and the DNA G+C content was 63.7 mol%. On the basis of our polyphasic taxonomic investigation, strain JRM2-1T is considered to represent a novel species in the genus Burkholderia, for which the name Burkholderia jirisanensis sp. nov. is proposed. The type strain is JRM2-1T ( = AIM 0373T = KCTC 42072T = JCM 19985T).

A brown alga Saccharina japonica and rice straw are attractive feedstock for microbial butyric acid production. However, inefficient fermentation of mannitol (a dominant component in S. japonica) and toxicity of inhibitors in lignocellulosic hydrolysate are limitations. This study demonstrated that mixed biomass with S. japonica and rice straw was effective in butyric acid production over those restrictions. Mannitol was consumed only when acetic acid was present. Notably, acetic acid was not produced but consumed along with mannitol. By mixing S. japonica and rice straw to take advantage of glucose and acetic acid in rice straw, Clostridium tyrobutyricum effectively consumed mannitol by utilizing acetic acid in hydrolysate and acetic acid derived from glucose with the enhanced butyric acid production. Furthermore, cell growth was restored owing to the decreased inhibitor concentration. The results demonstrate the potential of butyric acid production from mixed biomass of macroalgae/lignocellulose overcoming the drawbacks of single biomass.

Additional file 2: Table S2. Metabolism-related genes with significantly changed expression levels in XUSE relative to those in XUS.

Efficient isolation of lignocellulolytic bacteria is essential for the utilization of lignocellulosic biomass. In this study, bacteria with cellulolytic, xylanolytic, and lignolytic activities were isolated from environmental sites such as mountain, wetland, and mudflat using isolation media containing the combination of lignocellulose components (cellulose, xylan, and lignin). Eighty-nine isolates from the isolation media were characterized by analyzing taxonomic ranks and cellulolytic, xylanolytic, and lignolytic activities. Most of the cellulolytic bacteria showed multienzymatic activities including xylanolytic activity. The isolation media without lignin were efficient in isolating bacteria exhibiting multienzymatic activities even including lignolytic activity, whereas a lignin-containing medium was effective to isolate bacteria exhibiting lignolytic activity only. Multienzymatic activities were mainly observed in Bacillus and Streptomyces, while Burkholderia was the most abundant genus with lignolytic activity only. This study provides insight into isolation medium for efficient isolation of lignocellulose-degrading microorganisms.

Bioethanol production from lignocellulosic biomass for use as an alternative energy resource has attracted increasing interest, but short-term commercialization will require several technologies such as low cost feedstock. The huge amount of oil palm empty fruit bunches (EFB) generated from palm oil industries can be used as a raw material for cheap, renewable feedstock for further commercial exploitation. Using a pilot-scale bioethanol plant, this study investigated the possibility of utilizing oil palm empty fruit bunches as a renewable resource. All bioethanol production processes such as pretreatment, hydrolysis, fermentation, and purification were constructed as automatically controlled integrated processes. The mass balance was calculated from operational results. Changhae ethanol multiexplosion pretreatment with sodium hydroxide was conducted to improve the enzymatic hydrolysis process, and a separate hydrolysis and fermentation process was used for producing bioethanol at an 83.6% ethanol conversion rate. In order to purify the ethanol, a distillation and dehydration facility was operated. Distillation and dehydration efficiencies were 98.9% and 99.2%, respectively. The material balance could be calculated using results obtained from the operation of the pilot-scale bioethanol plant. As a result, it was possible to produce 144.4 kg anhydrous ethanol (99.7 wt%) from 1000 kg EFB. This result constitutes a significant contribution to the feasibility of bioethanol production from lignocellulosic biomass and justifies the pilot plant's scale-up to a commercial-scale plant.

In the thermochemical cycles such as the SI (sulfur–iodine) cycle, the Westinghouse process, and Ispra Mark 13 process, SO2 needs to be separated and purified to enhance system efficiency. As novel absorbents with non-volatility, thermal stability and high SO2 absorption capability, the characteristics of ionic liquids (ILs) as SO2 absorbents were investigated to separate SO2 in SO2/O2 gaseous mixtures from the sulfuric acid decomposer. SO2 absorption and desorption experiments showed that SO2 solubility and absorption rate in ILs were influenced mainly by anions of ILs. [BMIm][Cl] and [BMIm][OAc] (1.40–1.69 SO2 gmol/ILs gmol) showed the highest SO2 solubility among the tested ILs at 50 °C and 0.67 atm P SO 2 . Interestingly, [BMIm][OAc] showed irreversibility in the cycle of absorption and desorption. [BMIm][MeSO4] showed moderate SO2 solubility and good reversible cycles of absorption and desorption. The dependency of temperature and pressure on SO2 solubility of [BMIm][MeSO4] was scrutinized.

The reforming process of gasoline is an attractive technique for fuel processor or hydrogen station applications. We investigated catalytic autothermal reforming (ATR) of iso-octane and toluene over transition metal supported catalysts. The catalysts were prepared by an incipient wetness impregnation method and characterized by N2 physisorption, XRD, and TEM techniques before and after the reaction. Many of the tested catalysts displayed reasonably good activity towards the reforming reactions of iso-octane. Especially, Ni/Fe/MgO/Al2O3 catalyst showed more activity than the other catalysts tested in this study including commercial HT catalyst. Ni/Fe/MgO/Al2O3 catalyst showed good stability for 700 h in the ATR of iso-octane. No major change was observed in catalytic activity in ATR of iso-octane or in the structure of catalyst. Since iso-octane, toluene are surrogates of gasoline, Ni/Fe/MgO/Al2O3 catalyst can be considered as ATR catalyst for gasoline fuel processor and hydrogen station systems.

The iodine–sulfur (IS) cycle has been focused for hydrogen production by water splitting using a very high temperature nuclear reactor (VHTR) which is a high temperature heat source. The nuclear energy was absorbed at the temperature ranges of 750–900 °C by SO 3 decomposition reaction to SO 2 and O 2 in IS cycle. In this work, the activity of Fe/Al and Fe/Ti catalysts prepared by a co-precipitation was studied in an attempt to find some suitable catalysts for the decomposition of sulfur trioxide as the oxygen-generating reaction in the thermo-chemical water splitting process. The SO 3 decomposition was performed in the temperature range of 750–950 °C at a space velocity of 72,000 cm 3 /g cat. h in a fixed bed reactor. The catalytic activity of Fe/Al and Fe/Ti catalysts increased with an increase in Fe loadings, indicating that the Fe component should be active. The mechanism for the SO 3 decomposition on metal oxides can be described as follows: the metal sulfate formation (MO + SO 3 → MSO 4 ) and the decomposition of metal sulfate (MSO 4 → MO 2 + SO 2 and MO 2 → MO + 1/2O 2 ).

In the biorefinery using lignocellulosic biomass as feedstock, pretreatment to breakdown or loosen lignin is important step and various approaches have been conducted. For biological pretreatment, we screened Bacillus subtilis KCTC2023 as a potential lignin-degrading bacterium based on veratryl alcohol (VA) oxidation test and the putative heme-containing dye-decolorizing peroxidase was found in the genome of B. subtilis KCTC2023. The peroxidase from B. subtilis KCTC2023 (BsDyP) was capable of oxidizing various substrates and atypically exhibits substrate-dependent optimum temperature: 30 degrees C for dyes (Reactive Blue19 and Reactive Black5) and 50 degrees C for high redox potential substrates (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid [ABTS], VA, and veratryl glycerol-beta-guaiacyl ether [VGE]) over +1.0 V vs. normal hydrogen electrode. At 50 degrees C, optimum temperature for high redox potential substrates, BsDyP not only showed the highest VA oxidation activity (0.13 Umg(-1)) among the previously reported bacterial peroxidases but also successfully achieved VGE decomposition by cleaving C-alpha-C-beta bond in the absence of any oxidative mediator with a specific activity of 0.086 Umg(-1) and a conversion rate of 53.5%. Based on our results, BsDyP was identified as the first bacterial peroxidase capable of oxidizing high redox potential lignin-related model compounds, especially VGE, revealing a previously unknown versatility of lignin degrading biocatalyst in nature.

Detoxification process of cellular inhibitors including furfural is essential for production of bio-based chemicals from lignocellulosic biomass. Here we isolated an extreme furfural-tolerant bacterium Enterobacter cloacae GGT036 from soil sample collected in Mt. Gwanak, Republic of Korea. Among isolated bacteria, only E. cloacae GGT036 showed cell growth with 35 mM furfural under aerobic culture. Compared to the maximal half inhibitory concentration (IC50) of well-known industrial strains Escherichia coli (24.9 mM furfural) and Corynebacterium glutamicum (10 mM furfural) based on the cell density, IC50 of E. cloacae GGT036 (47.7 mM) was significantly higher after 24 h, compared to E. coli and C. glutamicum. Since bacterial cell growth was exponentially inhibited depending on linearly increased furfural concentrations in the medium, we concluded that E. cloacae GGT036 is an extreme furfural-tolerant bacterium. Recently, the complete genome sequence of E. cloacae GGT036 was announced and this could provide an insight for engineering of E. cloacae GGT036 itself or other industrially relevant bacteria.

An obligately aerobic, chemoheterotrophic, mesophilic prosthecate bacterium, designated strain CGM1-3ENT, was isolated from the enrichment cultures of forest soil from Cheonggyesan Mountain, Republic of Korea. Cells were Gram-reaction-negative, motile rods (1.3–2.4 µm long by 0.30–0.75 µm wide) with single flagella. The strain grew at 10–37 °C (optimum 25–30 °C) and at pH 4.5–9.5 (optimum 5.0–7.0). The major cellular fatty acids were C16 : 0, C18 : 1ω7c 11-methyl, C12 : 1 3-OH and summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c). The genomic DNA G+C content of strain CGM1-3ENT was 63.7 mol%. The closest phylogenetic neighbour to strain CGM1-3ENT was identified as Asticcacaulis biprosthecium DSM 4723T (97.2 % 16S rRNA gene sequence similarity) and the DNA–DNA hybridization value between strain CGM1-3ENT and A. biprosthecium DSM 4723T was less than 24.5 %. Strain CGM1-3ENT used d-glucose, d-fructose, sucrose, maltose, trehalose, d-mannose, d-mannitol, d-sorbitol, d-galactose, cellobiose, lactose, raffinose, fumarate, pyruvate, dl-alanine and glycerol as carbon sources. Based on data from the present polyphasic study, the forest soil isolate CGM1-3ENT is considered to represent a novel species of the genus Asticcacaulis , for which the name Asticcacaulis solisilvae sp. nov. is proposed. The type strain is CGM1-3ENT ( = AIM0088T = KCTC 32102T = JCM 18544T).

Enterobacter cloacae is a facultative anaerobic bacterium to be an important cause of nosocomial infection. However, the isolated E. cloacae GGT036 showed higher furfural-tolerant cellular growth, compared to industrial relevant strains such as Escherichia coli and Corynebacterium glutamicum. Here, we report the complete genome sequence of E. cloacae GGT036 isolated from Mt. Gwanak, Seoul, Republic of Korea. The genomic DNA sequence of E. cloacae GGT036 will provide valuable genetic resources for engineering of industrially relevant strains being tolerant to cellular inhibitors present in lignocellulosic hydrolysates.