5 research outputs found

    Extraction of the wheat straw hemicellulose fraction assisted by commercial endo-xylanases. Role of the accessory enzyme activities

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    Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGWheat straw is a highly promising raw material for bio-refinery strategies. Most of the literature related to lignocellulose fractionation focuses on cellulose purification and hemicellulose solubilization. Pre-treatments for hemicellulose solubilization without the formation of undesired products usually reach low extraction yields, which leaves an important hemicellulose fraction unused. In this work, we propose a mild process for the efficient extraction of the hemicellulose fraction of wheat straw assisted by partial enzymatic hydrolysis with three commercial endo-xylanase cocktails. A first step with alkali at 40 ºC helped to disrupt the lignocellulosic structure and removed 19% of lignin while maintaining most of the hemicellulose in the solid. The enzymatic step enabled reaching extraction yields of 59.8%, 51.9%, and 42.5% with Ultraflo L, Pentopan mono conc, and Shearzyme 500L, respectively. We also discuss the catalytic properties of each endo-xylanase, in particular, their adscription to the GH10 or GH11 glycosyl hydrolase family, and the relevant role of accessory enzymes.Agencia Estatal de Investigación | Ref. RTI2018–099249-B-I0

    Modelling the biphasic growth and product formation by Enterococcus faecium CECT 410 in realkalized fed-batch fermentations in whey

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    The influence of initial pH on growth and nutrient (total sugars, nitrogen, and phosphorous) consumption by Enterococcus faecium CECT 410 was studied during batch cultures in whey. With these data, two realkalized fed-batch fermentations were developed using different feeding substrates. The shift from homolactic to mixed acid fermentation, the biphasic kinetics observed for cell growth and nitrogen consumption and the increase in the concentrations of biomass and products (lactic acid, acetic acid, ethanol, and butane-2,3-diol) were the most noteworthy observations of these cultures. Modelling the fed-batch growth of Ent. faecium with the Logistic and bi-Logistic models was not satisfactory. However, biomass production was best mathematically described with the use of a double Monod model, which was expressed in terms of biomass, product accumulation, and nitrogen utilization. Product formation was successfully modelled with a modified form of the Luedeking and Piret model developed in this study.Instituto Nacional de Investigación y Tecnología Agraria | Ref. CAL01-045-C2-2Ministerio de Educación y Ciencia | Ref. MAT2005-05393-C03-03Ministerio de Educación y Ciencia | Ref. MAT2006-11662- C03-0

    Mepanipyrim residues on pasteurized red must influence the volatile derived compounds from Saccharomyces cerevisiae metabolism

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    The impact of mepanipyrim (Mep) and its corresponding commercial formulation (Mep Form) on Saccharomyces cerevisiae metabolites was assessed, separately, by using laboratory-scale wine fermentation assays on pasteurized red must. The presence of Mep did not alter the fermentation course. With regard to volatiles formed at the intracellular level by fermenting yeast cells, Mep residues affected mainly the acetate and ethyl ester biochemical pathways. In particular, the target acetates showed a notorious increment, >90%, in presence of commercial Mep Form at the higher dose assayed. The addition of Mep and Mep Form, at both tested levels, highly increased ethyl caprylate (between 42 and 63%) and ethyl caprate (between 36 and 60%) contents as the same as their respective fatty acid precursors. No important effects were observed on colour and non-volatile pyranoanthocyanins, probably due to the low anthocyanin content characteristic of pasteurized musts.Xunta de Galicia | Ref. EM2013/004POCTEP | Ref. 0377_IBERPHENOL_6_EMinisterio de Economía y Competitividad | Ref. AGL2015-66491-C2-1-

    Biochemical and structural characterization of a novel thermophilic esterase EstD11 provide catalytic insights for the HSL family

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    [Abstract]: A novel esterase, EstD11, has been discovered in a hot spring metagenomic library. It is a thermophilic and thermostable esterase with an optimum temperature of 60 C. A detailed substrate preference analysis of EstD11 was done using a library of chromogenic ester substrate that revealed the broad substrate specificity of EstD11 with significant measurable activity against 16 substrates with varied chain length, steric hindrance, aromaticity and flexibility of the linker between the carboxyl and the alcohol moiety of the ester. The tridimensional structures of EstD11 and the inactive mutant have been determined at atomic resolutions. Structural and bioinformatic analysis, confirm that EstD11 belongs to the family IV, the hormone-sensitive lipase (HSL) family, from the α/β-hydrolase superfamily. The canonical a/b hydrolase domain is completed by a cap domain, composed by two subdomains that can unmask of the active site to allow the substrate to enter. Eight crystallographic complexes were solved with different substrates and reaction products that allowed identification of the hot-spots in the active site underlying the specificity of the protein. Crystallization and/or incubation of EstD11 at high temperature provided unique information on cap dynamics and a first glimpse of enzymatic activity in vivo. Very interestingly, we have discovered a unique Met zipper lining the active site and the cap domains that could be essential in pivotal aspects as thermo-stability and substrate promiscuity in EstD11Ministerio de Ciencia e Innovación; BFU2017-90030-

    Are there benefits from thermal bacteria for health? The hydrogenome role

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    In recent years, natural thermal mineral waters have been gaining the special attention of the scientific community, namely in the prevention and treatment of some diseases, due to the microbial properties that exist in these habitats. The aim of this work was to characterize the physicochemical composition and the microbial taxonomic communities present in three thermal waters of the Galician region in Spain and two samples of the northern region in Portugal. These collected water samples were analyzed for physicochemical characterization and the respective hydrogenome of the waters using next generation sequencing together with 16S rRNA gene sequencing. The sequencing showed a high diversity of microorganisms in all analyzed waters; however, there is a clear bacterial predominance of Proteobacteria phylum, followed by Firmicutes, Deinococcus-Thermus, Aquificae and Nitrospira. The main physicochemical parameters responsible for the clustering within the Spanish waters were sulfur compounds (SO32− and S2−), CO32− and neutral pH, and in the Portuguese waters were Mg, Ca and Sr, nitrogen compounds (NO3− and NH4+), Na, Rb, conductivity and dry residue. This work will allow for a better understanding of the microbial community’s composition and how these microorganisms interfere in the physicochemical constitution of these waters often associated with medicinal properties. Furthermore, the hydrogenome may be used as an auxiliary tool in the practice of medical hydrology, increasing the likelihood of safe use of these unique water types.European Commission | Ref. (7PM / 2007-2013), n. 324439Xunta de Galicia | Ref. ED431C2018 / 55-GRCXunta de Galicia | Ref. ED431G2019 / 06Xunta de Galicia | Ref. ED431E 2018/07European Commission | Ref. NORTE-01-0145FEDER-030101 y PTDC / SAUINF / 30101/2017Fundação para a Ciência e a Tecnologia | Ref. UIDB / 50006/2020Fundação para a Ciência e a Tecnologia | Ref. UIDP / 50006/202
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