Melt viscoelastic assessment of Poly(Lactic Acid) composting: Influence of UV Ageing

This study is devoted to the degradation pathway (bio, photo degradation and photo/bio) of Poly(Lactic acid) PLA polymers by means of melt viscoelasticity. A comparison was made between three PLA polymers with different microstructures (L, D stereoisomers). Biodegradability was determined during composting by burying the polymer films in compost at 58 _C. Melt viscoelasticity was used to assess the molecular evolution of the materials during the composting process. Viscoelastic data were plotted in the complex plane. We used this methodology to check the kinetics of the molecular weight decrease during the initial stages of the degradation, through the evolution of Newtonian viscosity. After a few days in compost, the Newtonian viscosity decreased sharply, meaning that macromolecular chain scissions began at the beginning of the experiments. However, a double molar mass distribution was also observed on Cole-Cole plots, indicating that there is also a chain recombination mechanism competing with the chain scission mechanism. PLA hydrolysis was observed by infra-red spectroscopy, where acid characteristic peaks appeared and became more intense during experiments, confirming hydrolytic activity during the first step of biodegradation. During UV ageing, polymer materials undergo a deep molecular evolution. After photo-degradation, lower viscosities were measured during biodegradation, but no significant differences in composting were found. © 2018 by the authors

Detecting variants with Metabolic Design, a new software tool to design probes for explorative functional DNA microarray development

<p>Abstract</p> <p>Background</p> <p>Microorganisms display vast diversity, and each one has its own set of genes, cell components and metabolic reactions. To assess their huge unexploited metabolic potential in different ecosystems, we need high throughput tools, such as functional microarrays, that allow the simultaneous analysis of thousands of genes. However, most classical functional microarrays use specific probes that monitor only known sequences, and so fail to cover the full microbial gene diversity present in complex environments. We have thus developed an algorithm, implemented in the user-friendly program Metabolic Design, to design efficient explorative probes.</p> <p>Results</p> <p>First we have validated our approach by studying eight enzymes involved in the degradation of polycyclic aromatic hydrocarbons from the model strain <it>Sphingomonas paucimobilis </it>sp. EPA505 using a designed microarray of 8,048 probes. As expected, microarray assays identified the targeted set of genes induced during biodegradation kinetics experiments with various pollutants. We have then confirmed the identity of these new genes by sequencing, and corroborated the quantitative discrimination of our microarray by quantitative real-time PCR. Finally, we have assessed metabolic capacities of microbial communities in soil contaminated with aromatic hydrocarbons. Results show that our probe design (sensitivity and explorative quality) can be used to study a complex environment efficiently.</p> <p>Conclusions</p> <p>We successfully use our microarray to detect gene expression encoding enzymes involved in polycyclic aromatic hydrocarbon degradation for the model strain. In addition, DNA microarray experiments performed on soil polluted by organic pollutants without prior sequence assumptions demonstrate high specificity and sensitivity for gene detection. Metabolic Design is thus a powerful, efficient tool that can be used to design explorative probes and monitor metabolic pathways in complex environments, and it may also be used to study any group of genes. The Metabolic Design software is freely available from the authors and can be downloaded and modified under general public license.</p

Two-step fractionation of a model technical lignin by combined organic solvent extraction and membrane ultrafiltration

A fractionation method for technical lignin was developed, combining organic solvent extraction and membrane ultrafiltration of the solvent soluble component. This method was validated on a commercial wheat straw/Sarkanda grass lignin (Protobind 1000) using 2-butanone (MEK) as the solvent for both the extraction and the ultrafiltration operations. The parent lignin and the different obtained fractions were fully characterized in terms of chemical composition and physicochemical properties by gel permeation chromatography, gas chromatography/mass spectrometry (GC/MS), pyrolysis-GC/MS, total phenol contents, 31 P nuclear magnetic resonance ( 31 P NMR), thermogravimetric analysis, differential scanning calorimetry analysis, and Fourier-transform infrared spectroscopy. The results show that the proposed process allows a straightforward recovery of the different lignin fractions as well as a selective control over their molecular mass distribution and related dependent properties. Moreover, the operating flexibility of the Soxhlet/ultrafiltration process allows the treatment of lignins from different feedstocks using the same installation just by modulating the choice of the solvent and the membrane porosity with the best characteristics. This is one of the most important features of the proposed strategy, which represents a new fractionation approach with the potential to improve lignin valorization for materials science and preparative organic chemistry applications

Bacterial community changes during bioremediation of aliphatic hydrocarbon-contaminated soil

International audienceThe microbial community response during oxygen biostimulation process of aged oil-polluted soils is poorly documented and there is no reference for long-term monitoring of unsaturated zone. Two treatments (0 and 0.056 mol×h−1 molar flow rate of oxygen) were performed in fixed bed reactors containing oil-polluted soil in order to assess the potential effect of air-supplying on hydrocarbon fate and microbial community structure. Microbial activity was continuously monitored during two years throughout the oxygen biostimulation process. Microbial community structure before and after 12 and 24 months treatment was determined by a dual rRNA/rRNA gene approach allowing us to characterize bacteria which were presumably metabolically active and therefore responsible for the functionality of the community in this polluted soil. Clone library analysis revealed that the microbial community contained many rare phylotypes. These were never observed in other studied ecosystems. The bacterial community shifted from Gammaproteobacteria to Actinobacteria during the treatment. Without air supplying, the samples were dominated by a phylotype linked to the Streptomyces. Members belonging to eight dominant phylotypes were well adapted to air supplying process. The air supplying stimulated an Actinobacteria phylotype which might be involved in the restoring of the studied ecosystem. Phylogenetic analyses suggested that this phylotype is a novel, deep-branching member of the Actinobacteria related to the well studied genus Acidimicrobium

LIGNIN VALORIZATION: FROM MOLECULES TO MATERIALS

LIGNIN VALORIZATION: FROM MOLECULES TO MATERIALS Chiara Allegretti1*, Gianmarco Griffini1, Arno Cordes2, Simon Fontanay3, Alberto Strini4, Julien Troquet3, Stefano Turri1, Paola D’Arrigo1,5 1Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico of Milano, p.zza L. da Vinci 32, Milano, Italy 2ASA Spezialenzyme GmbH Am Exer 19 C, Wolfenbüttel, Germany 3Biobasic Environnement, Biopôle Clermont Limagne, Saint-Beauzire, France 4Construction Technologies Institute - National Research Council of Italy (ITC-CNR), San Giuliano Mil., Italy 5The Protein Factory Research Center, via Mancinelli 7, Milano, Italy *Corresponding author: [email protected] Lignin is a highly complex phenolic matrix that acts as a binder in plants conferring them structural integrity and strength, and is one of the three major subcomponents of lignocellulosic biomass. Although burning lignin is still considered a valuable contribution in saving fossil sources, the exploitation of this extremely abundant natural polymer in terms of higher value-added applications is very appealing as it represents the only viable source to produce aromatic compounds as fossil fuels alternative. Due to the very broad composition in terms of molecular weight of the raw material, a pretreatment strategy becomes necessary for an efficient lignin valorization as macromolecular building block for polymeric materials or as precursor for aromatic small molecules. To this end, a physical fractionation has been performed in this work, where Lignin (ProtobindTM1000) in a water/ethanol solution is subjected at first to microfiltration under vacuum in order to eliminate the insoluble residues. The permeate then undergoes a cross-flow filtration process using two subsequent membranes with cut-off of 3 kDa and 1 kDa. All the retentates and permeates have been fully characterized by GPC, GC-MS, ESI-MS, DSC, TGA and FT-IR. This procedure is an essential tool for a thorough exploitation of the main three different fractions recovered, namely a high, an intermediate and a low molecular weight fraction. The first one is characterized by the presence of high molecular weight polymers and is used without further chemical modification for developing bio-based polymeric materials;[1] the last one can be separated by chromatography into small aromatic molecules for preparative organic chemistry; whereas the middle fraction, characterized by an intermediate molecular weight, is the ideal starting material for oxidative depolymerization assays.[2,3] On this fraction, a new cascade process has been investigated involving at first a chemical/photochemical step aiming at a partial conversion of macromolecules to low molecular weight intermediates followed by a biocatalytic step performed by different classes of O2-dependent laccases (EC 1.10.3.2) in the presence of TEMPO as a mediator. Promising results have been obtained and extensive research is now in progress. Acknoledgements: COST Action CM1303 Systems Biocatalysis ValorPlus Project (grant agreement no FP7-KBBE-2013-7-613802

Multi-step fractionation as a tool for enhanced valorization of technical lignins: a model study

The valorisation of lignin obtained as a by-product of the pulping and biofuel industries is one of the most promising topics in the bioresource field. Despite its potential value as the only massively available aromatic biopolymer feedstock, technical lignin is nowadays mostly burnt as low cost energy source because of its chemical recalcitrance. The high heterogeneity of this material, largely dependent on the different vegetal sources and the specific biomass recovery methods, restricts its direct use and hinders also the optimization of depolymerisation approaches. The development of effective technical lignin fractionation strategies is therefore today one of the most challenging topic in the green chemistry field. In this study, the fractionation of an industrial commercial lignin was developed by a three step procedure set-up either in aqueous or in an environmentally friendly organic solvent in order to obtain sustainable and scalable processes.1,2 The first step consisted in a microfiltration or a Soxhlet extraction, depending on the type of solvent used. Then a cascade membrane-mediated ultrafiltration allowed to obtain at the end three refined lignin fractions. The parent lignin and the different lignin fractions were fully characterized. The two-step process reported here allows accessing lignin fractions with well-defined physico-chemical properties (including mass distribution, glass transition temperature, aliphatic and phenolic hydroxyl groups concentration, syringyl/guaiacyl unit ratio) and represents a valuable approach towards the development of bio-based polymers and the preparation of key platform chemicals, thereby paving the way for an effective exploitation and valorization of this remarkable resource. [1] Allegretti, C.; Fontanay, S.; Krauke, Y.; Luebbert, M.; Strini, A.; Troquet, J.; Turri, S.; Griffini, G.; D’Arrigo, P. ACS Sustainable Chem. Eng. 2018, 6, 9056-9064; DOI: 10.1021/acssuschemeng.8b01410. [2] Allegretti, C.; Fontanay, S.; Rischka, K.; Strini, A.; Troquet, J.; Turri, S.; Griffini, G.; D’Arrigo P. ACS Omega 2019, in press; DOI: 10.1021/acsomega.8b02851

Fractionation of Soda Pulp Lignin in Aqueous Solvent through Membrane-Assisted Ultrafiltration

An industrial wheat straw lignin was fractionated by a multistep process involving microfiltration followed by two membrane-assisted ultrafiltration steps starting from an aqueous solvent solution. The parent lignin and the different fractions were fully characterized in terms of chemical composition and physicochemical properties by gel permeation chromatography, gas chromatography–mass spectrometry, high-performance liquid chromatography, thermogravimetric analysis, differential scanning calorimetry analysis, and Fourier transform infrared spectroscopy. The results show that the proposed process allows us to selectively control the molar mass distribution of the fractions and the related dependent properties. This strategy offers a better understanding of the structural complexity of soda pulp raw lignin and emerges as an essential tool for lignin valorization in the context of material science and preparative organic chemistry