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Laccase treatment of phenolic compounds found in lignocellulosic hydrolysates is an alternative to reduce the growth inhibitory effect of these compounds on fermenting microorganisms. In order to d...

Despite a growing preference for second-generation (2G) ethanol in industries, its application is severely restricted owing to a major obstacle of developing a suitable yeast strain for fermentation using feedstock biomasses. In this study, a yeast strain, Saccharomyces cerevisiae A31Z, for 2G bioethanol production was developed from an industrial strain, Angel, using metabolic engineering by the incorporation of gene clusters involved in the xylose metabolism combined with adaptive evolution for evolving its anti-inhibitory properties. This strain outcompeted its ancestors in xylose utilization and subsequent ethanol production and manifested higher tolerance against common inhibitors from lignocellulosic hydrolysates, and also it lowered the production of glycerol by-product. Furthermore, A31Z outperformed in ethanol production using industrial hydrolysate from dried distillers grains with solubles and whole corn. Overall, this study provided a promising path for improving 2G bioethanol production in industries using S. cerevisiae.

Yeast-based bioethanol production from lignocellulosic hydrolysates (LH) is an attractive and sustainable alternative for biofuel production. However, the presence of acetic acid (AA) in LH is still a major problem. Indeed, above certain concentrations, AA inhibits yeast fermentation and triggers a regulated cell death (RCD) process mediated by the mitochondria and vacuole. Understanding the mechanisms involved in AA-induced RCD (AA-RCD) may thus help select robust fermentative yeast strains, providing novel insights to improve lignocellulosic ethanol (LE) production. Herein, we hypothesized that zinc vacuolar transporters are involved in vacuole-mediated AA-RCD, since zinc enhances ethanol production and zinc-dependent catalase and superoxide dismutase protect from AA-RCD. In this work, zinc limitation sensitized wild-type cells to AA-RCD, while zinc supplementation resulted in a small protective effect. Cells lacking the vacuolar zinc transporter Zrt3 were highly resistant to AA-RCD, exhibiting reduced vacuolar dysfunction. Moreover, zrt3Δ cells displayed higher ethanol productivity than their wild-type counterparts, both when cultivated in rich medium with AA (0.29 g L−1 h−1 versus 0.11 g L−1 h−1) and in an LH (0.73 g L−1 h−1 versus 0.55 g L−1 h−1). Overall, the deletion of ZRT3 emerges as a promising strategy to increase strain robustness in LE industrial production., This work was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of “Contrato-Programa” UIDB/04050/2020 - PE 20-23 and UIDB/04469/2020 unit. Cátia Santos-Pereira acknowledges the Ph.D. fellowship PD/BD/128032/2016 funded by FCT under the scope of the doctoral program in Applied and Environmental Microbiology (DP_AEM)., The authors acknowledge Helena Pereira for constructing the pRS413-Pep4- mCherry plasmid and Sara L. Baptista for the preparation of vine prune residue autohydrolysis liquors. BIOVINO project (0688_BIOVINO_6_E) funded by INTERREG España—Portugal and European Regional Development Fund (ERDF) is acknowledged for the supply of vine prune residues, info:eu-repo/semantics/publishedVersion

The antifungal and growth-stimulating activity of biological detoxification waste products of hydrolysates of lignocellulosic raw materials in vitro and in vivo was evaluated in comparison with reference preparations (Alirin-B, Fitosporin-M) and control (sterile tap water). These wastes are specially adapted microbocenoses of activated sludge, worked out in the process of purification of hydrolyzates of lignocellulosic raw materials from inhibitors of acetone butyl fermentation. The agronomic value of biodetoxification waste was studied in three prototypes of different nature, using Iren spring wheat as an example. The results showed that detoxification bioagents, regardless of origin, showed fungistatic activity at the in vitro and in vivo study stages (biotest). In an in vitro experiment, all test samples showed significant antifungal activity against the fungus F. oxysporum. The most effective was the biodetoxification waste obtained on the basis of microbocenosis of activated sludge grown on a nutrient medium containing phenol, formic and acetic acid. As a result of exposure to this bioagent at the end of the experiment, the average diameter of the colonies of the fungus F. oxysporum was approximately 34 times less than in the control version. The detoxification bioagent, obtained on the basis of a specially adapted microbocenosis of activated sludge grown on a nutrient medium simulating wastewater, reduced the diameter of phytopathogenic fungus colonies by an average of 16 times. Specially adapted activated sludge from the sewage treatment facilities of the wood processing enterprise, worked out during the detoxification of hydrolysates of lignocellulosic raw materials, was also able to effectively suppress fungus growth, the average diameter of which was 19 times less than the control. The biotest results also confirmed the fungistatic activity of the test samples. The effectiveness of reducing the total infection with seminal infections in different experimental variants ranged from 52 to 84%. The growth-promoting ability of biodetoxification waste was weak.

Background Lignocellulosic biomass is a promising resource of renewable biochemicals and biofuels. However, the presence of inhibitors existing in lignocellulosic hydrolysates (LCH) is a great challenge to acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum. In particular, phenolic compounds (PCs) from LCH severely block ABE production even at low concentrations. Thus, it is urgent to gain insight into the intracellular metabolic disturbances caused by phenolic inhibitors and elucidate the underlying mechanisms to identify key industrial bottlenecks that undermine efficient ABE production. Results In this study, a time-course of ABE fermentation by C. acetobutylicum in the presence of four typical PCs (syringaldehyde, vanillin, ferulic acid, and p-coumaric acid) was characterized, respectively. Addition of PCs caused different irreversible effects on ABE production. Specifically, syringaldehyde showed the greatest inhibition to butanol production, followed by vanillin, ferulic acid, and p-coumaric acid. Subsequently, a weighted gene co-expression network analysis (WGCNA) based on RNA-sequencing data was applied to identify metabolic perturbations caused by four LCH-derived PCs, and extract the gene modules associated with extracellular fermentation traits. The hub genes in each module were subjected to protein–protein interaction analysis and enrichment analysis. The results showed that functional modules were PC-dependent and shared some unique features. Specifically, p-coumaric acid caused the most extensive transcriptomic disturbances, particularly affecting the gene expressions of ribosome proteins and the assembly of flagella, DNA replication, repair, and recombination; the addition of syringaldehyde caused significant metabolic disturbances on the gene expressions of ribosome proteins, starch and sucrose metabolism; vanillin mainly disturbed purine metabolism, sporulation and signal transduction; and ferulic acid caused a metabolic disturbance on glycosyl transferase-related gene expressions. Conclusion This study uncovers novel insights into the inhibitory mechanisms of PCs for the first time and provides guidance for future metabolic engineering efforts, which establishes a powerful foundation for the development of phenol-tolerant strains of C. acetobutylicum for economically sustainable ABE production with high productivity from lignocellulosic biomass.

Biorefinery of biomass-based biofuels and biochemicals by microorganisms is a competitive alternative of traditional petroleum refineries. Zymomonas mobilis is a natural ethanologen with many desirable characteristics, which makes it an ideal industrial microbial biocatalyst for commercial production of desirable bioproducts through metabolic engineering. In this review, we summarize the metabolic engineering progress achieved in Z. mobilis to expand its substrate and product ranges as well as to enhance its robustness against stressful conditions such as inhibitory compounds within the lignocellulosic hydrolysates and slurries. We also discuss a few metabolic engineering strategies that can be applied in Z. mobilis to further develop it as a robust workhorse for economic lignocellulosic bioproducts. In addition, we briefly review the progress of metabolic engineering in Z. mobilis related to the classical synthetic biology cycle of “Design-Build-Test-Learn”, as well as the progress and potential to develop Z. mobilis as a model chassis for biorefinery practices in the synthetic biology era.

This paper investigates a new analytical technique for the quantitative detection of total sugar content in lignocellulosic hydrolysates by reaction headspace gas chromatography (HS-GC). By detecting the carbon dioxide (CO2) generated from the reaction between sugars in lignocellulosic hydrolysates and potassium dichromate, the total sugar content in lignocellulosic hydrolysates can be quantified. The data illustrate that the conversion of sugars in lignocellulose hydrolysates can be achieved under the given conditions (at 90 °C for 30 min), the relative standard deviation of this HS-GC technique in the total sugar content determination was within 3.35%, and the measured total sugar content in 15 lignocellulose hydrolysate samples closely matched those measured by the reference spectrophotometric technique (relative differences

Graphical abstract, Highlights • Characterisation of the spent sulphite liquor, a sugar-rich residue was done. • Four chromatographic methods for sugars and derivatives analysis were developed. • Cross-linked Pb+2 columns were suitable for fast and reliable sugars separation. • Cross-linked H+ columns were adequate for acids and furfurals separation. • Methods developed were successfully assayed on woody materials and hydrolysates., Waste from pulp and paper mills consist of sugar-rich fractions comprising hemicellulose derivatives and cellulose by-products. A complete characterisation of the waste streams is necessary to study the possibilities of an existing mill. In this work, four chromatographic methods have been developed to obtain the most suitable chromatographic method conditions for measuring woody feedstocks, lignocellulosic hydrolysates and cellulose pulp in sulphite pulping processes. The analysis of major and minor monosaccharides, aliphatic carboxylic acids and furfurals has been optimised. An important drawback of the spent liquors generated after sulphite pulping is their acidic nature, high viscosity and adhesive properties that interfere in the column lifetime. This work recommends both a CHO-782Pb column for the sugar analysis and an SH-1011 resin-based cross-linked gel column to separate low-molecular-weight chain acids, alcohols and furfurals. Such columns resulted in a good separation with long lifetime, wide pH operating range and low fouling issues.

Furfural, an inhibitor of yeast growth, occurs in xylose-containing lignocellulosic hydrolysates that are potential substrates for the fermentative production of the natural sweetener xylitol from xylose. Effects of furfural on growth and xylitol production by the yeast Candida magnoliae TISTR 5663 are reported. Aerobic as well as oxygen limited conditions were used to assess the effects of furfural. A mathematical model was developed to predict the behavior of this fermentation. The model was validated using independent experimental data. The model and its kinetic parameters are reported. Furfural was found to be a competitive inhibitor of growth. Nevertheless, the presence of a certain amount of furfural (∼0.3 g L −1 ) in the production medium actually improved the productivity of xylitol and its yield from xylose under suitable oxygen limited conditions.

Poacic acid, a decarboxylated product from 8–5-diferulic acid that is commonly found in monocot lignocellulosic hydrolysates, has been identified as a natural antifungal agent against economically significant fungi and oomycete plant pathogens. Starting from commercially available or monocot-derivable ferulic acid, a three-step synthetic procedure has been developed for the production of poacic acid needed for field testing in a controlled agricultural setting. First, ferulic acid was esterified to produce ethyl ferulate in 92% yield. Second, peroxidase-catalyzed free radical dehydrodimerization of ethyl ferulate produced crude diferulates, mainly 8–5-diferulate, in 91% yield. Finally, crystalline poacic acid was obtained in 25% yield via alkaline hydrolysis of the crude diferulates after purification by flash-column chromatography. This new procedure offers two key improvements relevant to large-scale production: 1) bubbling air through the reaction mixture in the second step to remove acetone greatly improves the recovery efficiency of the crude diferulates; and 2) telescoping minor impurities directly into the alkaline hydrolysis step eliminates the need for additional column purifications, thus reducing the overall cost of production and removing a major impediment to process scale-up.

Background Lignocellulosic biomass is a promising resource of renewable biochemicals and biofuels. However, the presence of inhibitors existing in lignocellulosic hydrolysates (LCH) is a great challenge to acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum. In particular, phenolic compounds (PCs) from LCH severely block ABE production even at low concentrations. Thus, it is urgent to gain insight into the intracellular metabolic disturbances caused by phenolic inhibitors and elucidate the underlying mechanisms to identify key industrial bottlenecks that undermine efficient ABE production. Results In this study, a time-course of ABE fermentation by C. acetobutylicum in the presence of four typical PCs (syringaldehyde, vanillin, ferulic acid, and p-coumaric acid) was characterized, respectively. Addition of PCs caused different irreversible effects on ABE production. Specifically, syringaldehyde showed the greatest inhibition to butanol production, followed by vanillin, ferulic acid, and p-coumaric acid. Subsequently, a weighted gene co-expression network analysis (WGCNA) based on RNA-sequencing data was applied to identify metabolic perturbations caused by four LCH-derived PCs, and extract the gene modules associated with extracellular fermentation traits. The hub genes in each module were subjected to protein–protein interaction analysis and enrichment analysis. The results showed that functional modules were PC-dependent and shared some unique features. Specifically, p-coumaric acid caused the most extensive transcriptomic disturbances, particularly affecting the gene expressions of ribosome proteins and the assembly of flagella, DNA replication, repair, and recombination; the addition of syringaldehyde caused significant metabolic disturbances on the gene expressions of ribosome proteins, starch and sucrose metabolism; vanillin mainly disturbed purine metabolism, sporulation and signal transduction; and ferulic acid caused a metabolic disturbance on glycosyl transferase-related gene expressions. Conclusion This study uncovers novel insights into the inhibitory mechanisms of PCs for the first time and provides guidance for future metabolic engineering efforts, which establishes a powerful foundation for the development of phenol-tolerant strains of C. acetobutylicum for economically sustainable ABE production with high productivity from lignocellulosic biomass.

SUMMARY Bioethanol production from lignocellulosic hydrolysates requires a producer strain that tolerates both the presence of growth and fermentation inhibitors and high ethanol concentrations. Therefore, we constructed heterozygous intraspecies hybrid diploids of Saccharomyces cerevisiae by crossing two natural S. cerevisiae isolates, YIIc17_E5 and UWOPS87-2421, a good ethanol producer found in wine and a strain from the flower of the cactus Opuntia megacantha resistant to inhibitors found in lignocellulosic hydrolysates, respectively. Hybrids grew faster than parental strains in the absence and in the presence of acetic and levulinic acids and 2-furaldehyde, inhibitors frequently found in lignocellulosic hydrolysates, and the overexpression of YAP1 gene increased their survival. Furthermore, although originating from the same parental strains, hybrids displayed different fermentative potential in a CO2 production test, suggesting genetic variability that could be used for further selection of desirable traits. Therefore, our results suggest that the construction of intraspecies hybrids coupled with the use of genetic engineering techniques is a promising approach for improvement or development of new biotechnologically relevant strains of S. cerevisiae. Moreover, it was found that the success of gene targeting (gene targeting fidelity) in natural S. cerevisiae isolates (YIIc17_E5α and UWOPS87-2421α) was strikingly lower than in laboratory strains and the most frequent off-targeting event was targeted chromosome duplication.

To avoid complex procedures in measurement of lipid content of oleaginous yeast especially for that can accumulate microbial lipid in lignocellulosic hydrolysates, fluorescent method using Nile Red as fluorescent dye was applied to measure lipid content of oleaginous yeast Trichosporon dermatis. The fluorescent method was built by fitting of lipid content identified by both conventional gravimetric method and fluorescence intensity of oleaginous yeast. Within the range of lipid content measured, the fitting curves showed linear relationship with good correlation coefficient (R2=0.95), showing this method is suitable for measuring lipid content of T. dermatis in the simulated medium. To evaluate the applicability of this method for lipid fermentation using lignocellulosic acid hydrolysates as substrate, T. dermatis was cultured in corncob acid hydrolysate and rice straw acid hydrolysate and then its lipid content measured by both fluorescent method and gravimetric method were compared. The results showed that the lipid content measured by these two methods were close, therefore, this method was promising for the application in lipid fermentation in lignocellulosic acid hydrolysates.

The toxic fermentation inhibitors in lignocellulosic hydrolysates pose significant problems for the production of second-generation biofuels and biochemicals. Among these inhibitors, 5-(hydroxymethyl)furfural (HMF) and furfural are specifically well known. This study investigated the furfural and 5-HMF tolerance in Candida strains, which could be used for the development of advanced generation bioethanol processes. The 10 isolates of Candida were selected based on the cell growth and bioethanol production on YPD medium containing several concentrations of furfural and 5-HMF by using spectrophotometer and HPLC. Candida parapsilosis Y80 could grow and produce bioethanol in the medium that contains furfural and 5-HMF with a concentration of 60 mM and 40 mM, respectively. Based on the results, C. parapsilosis Y80 has potential activity in the development of bioethanol fermentation.

The aims of this work were to improve cell tolerance towards high concentrations of furfural and 5-hydroxymethylfurfural (HMF) of an osmotolerant strain of Wickerhamomyces anomalus by means of evolutionary engineering, and to determine its ethanol production under stress conditions. Cells were grown in the presence of furfural, HMF, either isolated or in combination, and under high osmotic pressure conditions. The most toxic condition for the parental strain was the combination of both furans, under which it was unable to grow and to produce ethanol. However, the tolerant adapted strain achieved a yield of ethanol of 0.43 g g-1glucose in the presence of furfural and HMF, showing an alcohol dehydrogenase activity of 0.68 mU mg protein-1. For this strain, osmotic pressure, did not affect its growth rate. These results suggest that W. anomalus WA-HF5.5strain shows potential to be used in second-generation ethanol production systems.

Acetic acid, a potential growth inhibitor, commonly occurs in lignocellulosic hydrolysates. The growth of Cupriavidus necator DSM 545 and production of poly(3-hydroxybutyrate) (PHB) by this bacterium in a glucose-based medium supplemented with various initial concentrations of acetic acid are reported. The bacterium could use both glucose and acetic acid to grow and produce PHB, but acetic acid inhibited growth once its initial concentration exceeded 0.5 g/L. As acetic acid is an unavoidable contaminant in hydrolysates used as sugar sources in commercial fermentations, a mathematical model was developed to describe its impact on growth and the production of PHB. The model was shown to satisfactorily apply to growth and PHB production data obtained in media made with acetic-acid-containing hydrolysates of Napier grass and oil palm trunk as carbon substrates.

Background Formic acid is an inhibitory compound present in lignocellulosic hydrolysates. Understanding the complex molecular mechanisms underlying Saccharomyces cerevisiae tolerance to this weak acid at the system level is instrumental to guide synthetic pathway engineering for robustness improvement of industrial strains envisaging their use in lignocellulosic biorefineries. Results This study was performed to identify, at a genome-wide scale, genes whose expression confers protection or susceptibility to formic acid, based on the screening of a haploid deletion mutant collection to search for these phenotypes in the presence of 60, 70 and 80 mM of this acid, at pH 4.5. This chemogenomic analysis allowed the identification of 172 determinants of tolerance and 41 determinants of susceptibility to formic acid. Clustering of genes required for maximal tolerance to this weak acid, based on their biological function, indicates an enrichment of those involved in intracellular trafficking and protein synthesis, cell wall and cytoskeleton organization, carbohydrate metabolism, lipid, amino acid and vitamin metabolism, response to stress, chromatin remodelling, transcription and internal pH homeostasis. Among these genes is HAA1 encoding the main transcriptional regulator of yeast transcriptome reprograming in response to acetic acid and genes of the Haa1-regulon; all demonstrated determinants of acetic acid tolerance. Among the genes that when deleted lead to increased tolerance to formic acid, TRK1, encoding the high-affinity potassium transporter and a determinant of resistance to acetic acid, was surprisingly found. Consistently, genes encoding positive regulators of Trk1 activity were also identified as formic acid susceptibility determinants, while a negative regulator confers protection. At a saturating K+ concentration of 20 mM, the deletion mutant trk1Δ was found to exhibit a much higher tolerance compared with the parental strain. Given that trk1Δ accumulates lower levels of radiolabelled formic acid, compared to the parental strain, it is hypothesized that Trk1 facilitates formic acid uptake into the yeast cell. Conclusions The list of genes resulting from this study shows a few marked differences from the list of genes conferring protection to acetic acid and provides potentially valuable information to guide improvement programmes for the development of more robust strains against formic acid. Electronic supplementary material The online version of this article (doi:10.1186/s13068-017-0781-5) contains supplementary material, which is available to authorized users.

Supplementary data to this article can be found online at https:// doi.org/10.1016/j.biortech.2019.122054., This work presents the exploitation of waste industrial by-products as raw materials for the production of microbial lipids in engineered strains of the filamentous fungus Ashbya gossypii. A lipogenic xylose-utilizing strain was used to apply a metabolic engineering approach aiming at relieving regulatory mechanisms to further increase the biosynthesis of lipids. Three genomic manipulations were applied: the overexpression of a feedback resistant form of the acetyl-CoA carboxylase enzyme; the expression of a truncated form of Mga2, a regulator of the main 9 desaturase gene; and the overexpression of an additional copy of DGA1 that codes for diacylglycerol acyltransferase. The performance of the engineered strain was evaluated in culture media containing mixed formulations of corn-cob hydrolysates, sugarcane molasses or crude glycerol. Our results demonstrate the efficiency of the engineered strains, which were able to accumulate about 40% of cell dry weight (CDW) in lipid content using organic industrial wastes as feedstocks., This work was supported by: the Spanish Ministerio de Economía y Competitividad (grant numbers BIO2014-56930-PandBIO2017-88435R) and the Junta de Castilla y León (grant number SA016P17); the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019, PhD grant PD/ BD/113812/2015 to R. Silva (Doctoral Program in Applied and Environmental Microbiology), the MultiBiorefinery project (POCI-010145-FEDER-016403) and the BioTecNorte operation (NORTE-010145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. DDF was recipient of USAL predoctoral fellowship from the University of Salamanca., info:eu-repo/semantics/publishedVersion

In the present study we investigated the possibility of using the waste of the lignocellulosic hydrolysates biodetoxification as a seed treater for wheat varieties zoned in the West Siberian region including the Tomsk region. The wastes are microbiocenoses of activated sludge, depleted during the detoxification process and capable of growing on toxic substrates. The study was conducted on three experimental objects and on wheat varieties Iren, Novosibirskaya 3, Novosibirskaya 51. For comparison, reference objects of biological preparations for plant protection Alirin-B, Fitosporin-M were used. The study showed that the waste of lignocellulosic hydrolysates biodetoxification had antifungal activity. The effectiveness of reducing the total contamination of seed infection in different experiments with experimental samples ranged from 52 to 82%. In some cases, the reference variants proved to be ineffective; the maximum effect on reducing the total seed contamination was achieved by Alirin-B and amounted about 30%. Seed treatment of wheat by the waste biodetoxification of different origins reduced the prevalence pathogens of seed wheat. At the same time the treatment did not significantly affect the increase in the parameters of plant growth and development (germination, length and weight of sprouts).

Microbial chemicals and fuels production from renewable resources requires the development of biocatalysts that can tolerate toxic chemicals produced during the lignocellulosic hydrolyzation process and also tolerate the end product toxicity. Evolutionary engineering makes use of adaptive strategies and selection procedures to generate and study mutations that will increase tolerance to harmful chemicals and therefore increase productivity and titer in such processes. In this chapter, we will review recent advances in evolutionary engineering strategies, their results and challenges to generate better microorganisms for the production of chemicals and fuels from lignocellulosic hydrolysates.

The concentration of polymerised sugars in enzymic hydrolysates from lignocellulosic materials was determined by high pressure liquid chromatography (h.p.l.c.) of hydrolysates before and after dilute acid hydrolysis: significant quantities of polymerised glucose and xylose were found in lignocellulosic hydrolysates, and these accounted for the discrepancy between the dinitrosalicyclic acid (DNS) and h.p.l.c. assay methods.

The dinitrosalicylic acid (DNS) method gives a rapid and simple estimation of the extent of saccharification by measuring the total amount of reducing sugars in the hydrolysate. However, it is subject to interference by citrate buffer and other substances and by the differing reactivities of the various reducing sugars. These interferences become more apparent when complex substrates such as sugar cane bagasse are employed. The paper also shows how the DNS method can be adapted for use on a Technicon Autoanalyser.

Aims: To show that the ethanol-induced lag phase in yeast can be almost eliminated by combining pre-adaptation with acetaldehyde supplementation. Methods and Results: Pre-adaptation to noninhibitory concentrations of ethanol and supplementation of unadapted cultures with acetaldehyde each separately reduced the lag phase of ethanol-inhibited cultures by c. 70%. By combining the two methods the ethanol-induced lag phase was virtually eliminated (90% reduction in lag time). Conclusions: Pre-adaptation to ethanol and acetaldehyde supplementation appear to promote yeast growth through different mechanisms, which are additive when combined. Significance and Impact of the Study: The combination of the above procedures is a potentially powerful tool for reducing the lag of stressed cultures, which may have practical applications: e.g. in reducing the lag of yeasts inoculated into lignocellulosic hydrolysates employed in fuel ethanol production.

Supercritical fluid extraction of a lignocellulosic hydrolysate of spruce for detoxification and to facilitate analysis of inhibitors

The production of chemicals from lignocellulosics continues to be an active area of research. Improved economics for lignocellulosic-based chemical production processes can be realized through the integration of these processes into existing bioprocessing facilities that are often described as biorefineries. The focus of some of the most recent work in this area is the topic of session 5. Research described by the speakers in this session illustrates the capturing of additional value from low value coproducts and alternative products from several industries. Examples from the talks include the production of fuels such as ethanol and biodiesel from industrial processing co-products; increased value from feed fibers as provided in the talk on the corn processing industry; multiple products and co-products from woody biomass and sugarcane fiber lignins; and syngas from glycerol obtained as a byproduct from vegetable oil processing to biodiesel. While many of the presentations provided an overview of the employment of separation technologies to biomass feedstocks, one presentation directly highlighted the impediments to the production of polyols by chemical catalysis of lignocellulosic feedstocks. Since a similar problem exists in microbial biocatalyst inhibition by lignocellulosic hydrolysates, the development of innovative pretreatment, hydrolysis and separation technologies to overcome microbial inhibition and catalyst poisoning will be essential for progress in this area.

Dear Readers, Microbial Biotechnology (MBT) is undergoing a number of interesting changes that we would like to report. The first is its transition to an author-pays open access model from 2013. We believe open access will offer the journal a number of advantages, including the flexibility to grow without the constraints of a page budget, and substantial increases in exposure, with all articles being made freely available via Wiley Online Library and PubMed Central. MBT's transition to open access will significantly benefit both authors and readers, and hence the field of biotechnology as a whole. The Journal will continue to be editorially independent and its editorial team will continue to apply ever increasing standards of peer review, thus ensuring that the journal continues to be the high quality publication we know and value. Another is that MBT was assigned its first Impact Factor at the end of June and, since that time, has experienced a significant increase in submissions. As has been the case with its sister journals, Environmental Microbiology and Environmental Microbiology Reports, this rise in submissions will translate into an Editor-implemented rise in quality–originality threshold for acceptance, which in turn will positively influence subsequent IFs. Given the steady increase in exciting science we receive, we are confident that MBT will experience healthy increases in IF over the coming years. An important characteristic of MBT is the strength of its Editorial team – its Editors, Editorial Board and army of ad hoc reviewers, composed of leaders in the different sectors of microbial biotechnology, leaders both in the sense of representing the field and in pioneering the way forward. It is these dedicated scientists who set the benchmark for the field and for the papers that are published in MBT. They do this by providing constructive, critical reviews on submissions and by submitting their own work, and thereby ensure that MBT publishes some of the best research from high profile groups. The Editors are deeply indebted to the dedicated selfless support of its Editorial Board and ad hoc reviewers: thank you all for your tremendous support! The declared goal of MBT is to promote the field of applied microbiology, inter alia by stimulating young researchers to carry out original research on novel topics at the interfaces of the various disciplines that impact on biotechnology. It does so not only by showcasing important developments by leading groups, but also by profiling topics and new developments the Editors consider will lead to ground-breaking discoveries. One means it employs to do this is to publish Special and Themed Issues on such topics, edited by top researchers in the field. Exciting recent ones have been on Microbial Vaccines and Immunomodulators (http://onlinelibrary.wiley.com/doi/10.1111/mbt.2012.5.issue-2/issuetoc) edited by Carlos Guzman, Ennio de Gregorio, Jan ter Meulen and Martin Friede, and Microbial Resource Mangement (http://onlinelibrary.wiley.com/doi/10.1111/mbt.2012.5.issue-3/issuetoc), edited by Nico Boon and Willy Verstraete. Another means is the Web Alert of Larry Wackett which assembles the best websites for relevant diverse aspects of applied microbiology. A third is the biannual original, sometimes provocative, Crystal Ball series, in which international experts speculate on the key new developments/theories/paradigms that will drive discoveries in the field over the following years. This feature, which appears in the first issue of the year, always creates considerable interest and, in some cases, amusement. Take a look at the 2013 CB in this issue. And finally: check out below the most downloaded and most cited papers in MBT (see the MBT website for latest updates) to see who is publishing what in hot interest-generating biotechnology. Top downloaded articles Marine genomics: at the interface of marine microbial ecology and biodiscovery Karla B. Heidelberg, Jack A. Gilbert, Ian Joint Bacterial persistence increases as environmental fitness decreases Seok Hoon Hong, Xiaoxue Wang, Hazel F. O'Connor, Michael J. Benedik, Thomas K. Wood Strategies for discovery and improvement of enzyme function: state of the art and opportunities Praveen Kaul, Yasuhisa Asano Natural products for cancer chemotherapy Arnold L. Demain and Preeti Vaishnav Anaerobic benzene degradation by bacteria Carsten Vogt, Sabine Kleinsteuber, Hans-Hermann Richnow Top cited articles Metabolic engineering to enhance bacterial hydrogen production Maeda, T; Sanchez-Torres, V; Wood, TK Identification of furfural as a key toxin in lignocellulosic hydrolysates and evolution of a tolerant yeast strain Heer, D; Sauer, U Microbial degradation of lignin: how a bulky recalcitrant polymer is efficiently recycled in nature and how we can take advantage of this Ruiz-Duenas, FJ; Martinez, AT Microbial reporters of metal bioavailability Magrisso, S; Erel, Y; Belkin, S Indole and 7-hydroxyindole diminish Pseudomonas aeruginosa virulence Lee, J; Attila, C; Cirillo, SLG; Cirillo, JD; Wood, TK So, submit your best work to MBT, participate in its upward march to become the flagship of microbial biotechnology research, and your paper may be in one of these lists in future!

Two mutants of Pachysolen tannophilus were isolated which produced considerably more acetic acid from several sugars than a wild type strain. Such mutants are of potential interest for the production of acetic acid rather than ethanol from lignocellulosic hydrolysates.