Physical properties of a new dipeptide ionic liquid in water and methanol at several temperatures: Correlation and prediction

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe physical properties of choline glycylglycinate (ChGlyGly) were experimentally determined at several temperatures. The empirical values of density, refractive index, speed of sound and dynamic viscosity for aqueous and methanolic mixtures of this ionic liquid were also ascertained at different temperatures. From these values, isentropic compressibility, molar volume, free volume, isobaric thermal expansivity and molar refraction have been calculated along with critical parameters (temperature, volume and pressure), acentric factor and boiling point. From a theoretical point of view, derived values of the neat ChGlyGly and the corresponding mixtures have been ascertained in the abovementioned temperature interval. Polynomial fittings turned to suitably describe the obtained data while Redlich-Kister has been used to fit to the derived magnitudes. To conclude, the density of the mixtures has been successfully predicted at several temperatures for the first time by means of different modelsMinisterio de Ciencia, Innovación y Universidades | Ref. RTI2018-094702-B-I0

Design of novel aqueous two-phase systems to be coupled in biological remediation processes

The ability of a biodegradable Deep Eutectic Solvent (DES) reline to induce phase segregation in aqueous solutions of polymeric non-ionic surfactants (Tween 20 and Tween 80) has been demonstrated as a preliminary step to be employed for assisting a biological degradation process of a model contaminant. The binodal curves for systems composed of (surfactants + reline + Water) have been determined at several temperatures, and the experimental data have been correlated using well-known equations. The equilibrium data have been analysed in the light of the operating temperature and the hydrophobicity of surfactants. Tie-lines of these systems have been determined, together with useful parameters such as tie-line length and tie-line slopes. Othmer-Tobias and Bancroft equations have been applied to provide an adequate description of the equilibrium data. Finally, the application of this new approach for the remediation of aqueous polluted effluent has proven to be highly efficient, with extraction percentages exceeding 99% for two model persistent contaminants (Acid Black 48 and Crystal Violet). Consequently, this ATPS is proposed as an extra-stage to enhance the remediation percentagesachieved through biological methods. Furthermore, the process has been simulated using commercial software.Universidade de Vigo/CISU

Identification and characterization of the PhhR regulon in Pseudomonas putida

Pseudomonas putida is a soil microorganism that utilizes aromatic amino acids present in root exudates as a nitrogen source. We have previously shown that the PhhR transcriptional regulator induces phhAB genes encoding a phenylalanine hydroxylase. In this study we show, using microarray assays and promoter fusions, that PhhR is a global regulator responsible for the activation of genes essential for phenylalanine degradation, phenylalanine homeostasis and other genes of unknown function. Recently, it has been shown that phenylalanine catabolism occurs through more than one pathway. One of these possible pathways involves the metabolism of phenylalanine via tyrosine, p-hydroxyphenylpyruvate, and homogentisate. We identified two genes within this pathway that encode an acyl-CoA transferase involved in the metabolism of acetoacetate. All genes in this pathway were induced in response to phenylalanine in a PhhR-proficient background. The second potential degradative pathway involves the degradation of phenylalanine to produce phenylpyruvate, which seems to be degraded via phenylacetyl-CoA. A number of mutants in the paa genes encoding phenylacetyl-CoA degradation enzymes fail to grow on phenylpyruvate or phenylacetate, further supporting the existence of this second pathway. We found that the PhhR regulon also includes genes involved in the biosynthesis of aromatic amino acids that are repressed in the presence of phenylalanine, suggesting the possibility of feedback at the transcriptional level. In addition, we found that PhhR modulates the level of expression of the broad-substrate-specificity MexEF/OprN efflux pump. Expression from this pump is under the control of mexT gene product because phenylalanine-dependent transcription from the mexE promoter does not occur in a mexT mutant background. These results place PhhR as an important regulator in the control of bacterial responses to aromatic amino acids

Extracting extremophilic lipases from aqueous streams by using biocompatible ionic liquids

Financiado para publicación en acceso aberto:Universidade de Vigo/CISUGIn this work, biocompatible ionic liquids based on aminoacids were employed as extractants to separate extremolipases from aqueous streams. First, the influence of aminoacid and dipeptide-based ionic liquids (cholinium glycinate, ChGly, and cholinium glycylglycinate, ChGlygly) on the lipolytic activity of a commercial lipase from Candida antarctica (CaLB) and in-house synthesized extremophilic lipases from Thermus thermophilus HB27 (TtHB27L) and Halomonas sp. LM1C (HL) was investigated. The combination of thermophilic enzyme with ChGly turned out to be the optimum combination for maximizing the biocatalytic performance, clearly improving the levels attained when water was exclusively employed as solvent and also surpassing the activity levels provided for the commercial enzyme CaLB. The salting out capacity of ChGly in aqueous solutions of biodegradable surfactants Tergitol 15S7 and Tergitol 15S9 was discussed, recording immiscibility areas almost covering all the ternary diagrams. The aqueous biphasic systems were experimentally characterized by determining both tie-lines and solubility curves at several temperatures and the data was modelled with relevant equations like Merchuk, Othmer-Tobias and Bancroft ones, as they are the most common ones to describe this kind of equilibrium data. So, ChGly was applied to extract thermophilic and commercial lipases from aqueous solutions at 313.15 K, achieving very high extraction levels (about 100 %) for TtHB27L, which clearly surpasses the maximum extraction values observed for the commercial enzyme (about 80 %). Finally, the process was simulated at real scale through SuperPro Designer v.8.5 for the production of 385 Kg/year of extremolipaseXunta de Galicia | Ref. ED481D-2019/017Ministerio de Ciencia, Innovación y Universidades | Ref. RTI2018-094702-B-I0

Biorefining brewery spent grain polysaccharides through biotuning of ionic liquids

Brewery spent grain (BSG), a relevant waste from beer industry mainly composed of polysaccharides and lignin, is experiencing a surge in the production with its associated environmental impact. Thus, this manuscript bets in the application of aqueous solutions of a cholinium-based ionic liquid (IL) containing glycinate as anion ([N1112OH][Gly]) for an efficient delignification pretreatment. The operation at 90 °C yielded drastic lignin reduction (75.89%), greater than the levels attained when a traditional imidazolium-based IL (1-ethyl-3-methylimidazolium acetate, [C2C1im][C1COO]), was used (40.18%). The advantages of this pretreatment positively impacted the subsequent saccharification reaction, as the levels were increased up to about 1.5 times regarding the control (no IL) or the imidazolium-based pretreatment. ATR-FTIR spectrometry and scanning electron microscopy turned out to be useful tools to monitor the structural changes exerted. The results presented in this work make up the basis for a rational design of bio-ILs for delignification of lignocellulosic materials.Xunta de Galicia | Ref. ED431F 2016/007Ministerio de Economía y Competitividad | Ref. CTQ2015-71436-C2-1-

Choline dihydrogen phosphate-based deep eutectic solvent: a suitable bioplatform for lipase extraction

In this work, we have demonstrated the suitability of a novel Deep Eutectic Solvent (DES) composed of cholinium dihydrogen phosphate and ethylene glycol at a molar ratio of 1:2 (ChDHP:EG) to extract Candida antarctica lipase B from aqueous solutions of non-ionic surfactants Triton X-100 and Tween 80. The binodal curves were firstly explored at temperatures between 298.15 and 333.15 K and the experimental data were correlated by means of empirical models based on exponential and polynomial equations. The tie-lines have been ascertained by means of density and refractive indices measurement, and Othmer-Tobias, Bancroft and Setschenow equations were proposed to correlate these data. The Tween 80-based Aqueous Biphasic System was demonstrated to avoid any deleterious effect on the lipase biocatalytic activity, and more than 80% of the enzyme activity was retained on the DES-rich phase, which proves the suitability of these platforms to be employed in downstream stages in lipase production processes.Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGXunta de Galicia | Ref. ED481D-2019/017Xunta de Galicia | Ref. ED431F 2016/007Agencia Estatal de Investigación | Ref. RTI2018-094702-B-I0

Genomic analysis reveals the major driving forces of bacterial life in the rhizosphere

A global analysis of Pseudomonas putida gene expression performed during the interaction with maize roots revealed how a bacterial population adjusts its genetic program to the specific conditions of this lifestyle

Physico-chemical characterization of methanolic mixtures of cholinium dihydrogen phosphate-based DES

The biocompatibility of three deep eutectic solvents based on cholinium dihydrogen phosphate for their use in lipase-catalyzed reactions was recently demonstrated, so the possible application as cosolvents with methanol in transesterification processes demands an exhaustive characterization of the physical properties. Thus, in this work binary and ternary deep eutectic solvents composed of the abovementioned salt as hydrogen bond acceptor and ethyleneglycol and/or glycerol as hydrogen bond donors were synthesized and mixed with methanol. The density, refractive index, electrical conductivity and dynamic viscosity were determined between 293.15 K and 323.15 K. The experimental data were correlated with different well-known equations and derived magnitudes like excess molar volumes, changes of refractive index on mixing and viscosity deviations were inferred in order to get an in-depth characterization of the studied mixtures with cholinium dihydrogen phosphate-based DES. The most intriguing data observed is the great peak measured for ionic conductivity at very high methanol concentration, which is difficult to explain even with the most recent theoretical models.Agencia Estatal de Investigación | Ref. RTI2018-094702-B-I00Xunta de Galicia | Ref. ED481D-2019/017Universidade de Vigo/CISU

Genome-Wide Analysis of the Response of Dickeya dadantii 3937 to Plant Antimicrobial Peptides

Antimicrobial peptides constitute an important factor in the defense of plants against pathogens, and bacterial resistance to these peptides have previously been shown to be an important virulence factor in Dickeya dadantii, the causal agent of soft-rot disease of vegetables. In order to understand the bacterial response to antimicrobial pep- tides, a transcriptional microarray analysis was performed upon treatment with sub-lethal concentration of thionins, a widespread plant peptide. In all, 36 genes were found to be overexpressed, and were classified according to their deduced function as i) transcriptional regulators, ii) transport, and iii) modification of the bacterial membrane. One gene encoding a uricase was found to be repressed. The majority of these genes are known to be under the control of the PhoP/PhoQ system. Five genes representing the different functions induced were selected for further analysis. The results obtained indicate that the presence of antimicrobial peptides induces a complex response which includes peptide-specific elements and general stress-response elements contributing differentially to the virulence in different hosts

Creating a new biocatalytic complex with extremolipases and biocompatible ionic liquids for improved transesterification reactions

The ongoing energy crisis has spurred increased research into sustainable and more competitive methods for producing biofuels, including biodiesel. In this context, the focus of the current study is to underscore the viability of investing in a novel biocatalytic complex. This complex incorporates extremophilic lipases and biocompatible ionic liquids with the aim of achieving exceptionally high conversions in transesterification reactions without generating glycerol. Through a meticulous screening process encompassing various amino acid and dipeptide-based ionic liquids from the ammonium family, cholinium glycinate turned out to be the optimal choice. This selection was driven not only by its enhanced compatibility with a commercially available Candida antarctica lipase B (CaLB) but also with extremophilic enzymes synthesized in-house, derived from halophilic (Halomonas spLM1C) and thermophilic (Thermus thermophilus HB27) strains. Following rigorous testing of both free and immobilized enzymes, the ideal concentration of the ionic liquid in transesterification reactions was determined to be 1% relative to the sunflower oil content. Comparative analysis of conversion rates between immobilized thermophilic lipase and immobilized CaLB revealed the efficacy of the proposed approach. Maximum conversions were found to increase by 20%, with specific conversion rates soaring by approximately 180% when utilizing the immobilized thermophilic lipase. In conclusion, this research ushers in new prospects for advancing the competitiveness of biocatalytic solutions in glycerol-free transesterification reactions, underscoring its potential to revolutionize the landscape of sustainable energy production.Agencia Estatal de Investigación | Ref. RTI2018-094702-B-I00Xunta de Galicia | Ref. ED481D-2019/017Universidade de Vigo/CISU