Enlarging the tools for efficient enzymatic polycondensation: structural and catalytic features of cutinase 1 from Thermobifida cellulosilytica

9siCutinase 1 from Thermobifida cellulosilytica is reported for the first time as an efficient biocatalyst in polycondensation reactions. Under thin film conditions the covalently immobilized enzyme catalyzes the synthesis of oligoesters of dimetil adipate with different polyols leading to higher Mw (~1900) and Mn (~1000) if compared to lipase B from Candida antarctica or cutinase from Humicola insolens. Computational analysis discloses the structural features that make this enzyme readily accessible to substrates and optimally suited for covalent immobilization. As lipases and other cutinase enzymes, it presents hydrophobic superficial regions around the active site. However, molecular dynamics simulations indicate the absence of interfacial activation, similarly to what already documented for lipase B from Candida antarctica. Notably, cutinase from Humicola insolens displays a “breathing like” conformational movement, which modifies the accessibility of the active site. These observations stimulate wider experimental and bioinformatics studies aiming at a systematic comparison of functional differences between cutinases and lipases.partially_openembargoed_20161210Pellis, Alessandro; Ferrario, Valerio; Zartl, Barbara; Brandauer, Martin; Gamerith, Caroline; Herrero-Acero, Enrique; Ebert, Cynthia; Gardossi, Lucia; Guebitz, GeorgPellis, Alessandro; Ferrario, Valerio; Zartl, Barbara; Brandauer, Martin; Gamerith, Caroline; Herrero Acero, Enrique; Ebert, Cynthia; Gardossi, Lucia; Guebitz, Geor

Enzymatic surface hydrolysis of PET : effect of structural diversity on kinetic properties of cutinases from thermobifida

In this study cutinases from Thermobifida cellulosilytica DSM44535 (Thc_Cut1 and Thc_Cut2) and Thermobifida fusca DSM44342 (Thf42_Cut1) hydrolyzing poly(ethylene terephthalate) (PET) were successfully cloned and expressed in E.coli BL21-Gold(DE3). Their ability to hydrolyze PET was compared with other enzymes hydrolyzing natural polyesters, including the PHA depolymerase (ePhaZmcl) from Pseudomonas fluorescens and two cutinases from T. fusca KW3. The three isolated Thermobifida cutinases are very similar (only a maximum of 18 amino acid differences) but yet had different kinetic parameters on soluble substrates. Their kcat and Km values on pNP–acetate were in the ranges 2.4–211.9 s–1 and 127–200 μM while on pNP–butyrate they showed kcat and Km values between 5.3 and 195.1 s–1 and between 1483 and 2133 μM. Thc_Cut1 released highest amounts of MHET and terephthalic acid from PET and bis(benzoyloxyethyl) terephthalate (3PET) with the highest concomitant increase in PET hydrophilicity as indicated by water contact angle (WCA) decreases. FTIR-ATR analysis revealed an increase in the crystallinity index A1340/A1410 upon enzyme treatment and an increase of the amount of carboxylic and hydroxylic was measured using derivatization with 2-(bromomethyl)naphthalene. Modeling the covalently bound tetrahedral intermediate consisting of cutinase and 3PET indicated that the active site His-209 is in the proximity of the O of the substrate thus allowing hydrolysis. On the other hand, the models indicated that regions of Thc_Cut1 and Thc_Cut2 which differed in electrostatic and in hydrophobic surface properties were able to reach/interact with PET which may explain their different hydrolysis efficiencies.This study was performed within the Austrian Centre of Industrial Biotechnology ACIB, the MacroFun project and COST Action 868. This work has been supported by the Federal Ministry of Economy, Family and Youth (BMWFJ), the Federal Ministry of Traffic, Innovation and Technology (bmvit), the Styrian Business Promotion Agency SFG, the Standortagentur Tirol and ZIT - Technology Agency of the City of Vienna through the COMET-Funding Program managed by the Austrian Research Promotion Agency FFG. Financial support was also given from Sachsisches Staatsministerium fur Umwelt und Landwirtschaft, Germany. PET was kindly provided by Dr. Vincent Nierstrasz from Ghent University

Structural insight into molecular mechanism of poly (ethylene terephthalate) degradation

Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and thus are widely used in daily life. However, non-biodegradability, once thought to be an advantage offered by plastics, is causing major environmental problem. Recently, a PET-degrading bacterium, Ideonella sakaiensis, was identified and suggested for possible use in degradation and/or recycling of PET. However, the molecular mechanism of PET degradation is not known. Here we report the crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 angstrom resolution. IsPETase has a Ser-His-Asp catalytic triad at its active site and contains an optimal substrate binding site to accommodate four monohydroxyethyl terephthalate (MHET) moieties of PET. Based on structural and site-directed mutagenesis experiments, the detailed process of PET degradation into MHET, terephthalic acid, and ethylene glycol is suggested. Moreover, other PETase candidates potentially having high PET-degrading activities are suggested based on phylogenetic tree analysis of 69 PETase-like proteins

The 2010 very high energy gamma-ray flare & 10 years of multi-wavelength observations of M 87

Abridged: The giant radio galaxy M 87 with its proximity, famous jet, and very massive black hole provides a unique opportunity to investigate the origin of very high energy (VHE; E>100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of super-massive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (~day), peak fluxes (Phi(>0.35 TeV) ~= (1-3) x 10^-11 ph cm^-2 s^-1), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken ~3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core. The long-term (2001-2010) multi-wavelength light curve of M 87, spanning from radio to VHE and including data from HST, LT, VLA and EVN, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified.Comment: 19 pages, 5 figures; Corresponding authors: M. Raue, L. Stawarz, D. Mazin, P. Colin, C. M. Hui, M. Beilicke; Fig. 1 lightcurve data available online: http://www.desy.de/~mraue/m87

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

The enormous quantity of food wastes discarded annually force to look for alternatives for this interesting feedstock. Thus, food bio-waste valorisation is one of the imperatives of the nowadays society. This review is the most comprehensive overview of currently existing technologies and processes in this field. It tackles classical and innovative physical, physico-chemical and chemical methods of food waste pre-treatment and extraction for recovery of added value compounds and detection by modern technologies and are an outcome of the COST Action EUBIS, TD1203 Food Waste Valorisation for Sustainable Chemicals, Materials and Fuels

Renewable building blocks for sustainable polyesters: new biotechnological routes for greener plastics

5siThe next generation of plastics are expected to contribute to a massive reduction in the carbon footprint by the exploitation, in industrial productive processes, of renewablemonomers such as polyols and dicarboxylic acids obtainable via biotechnological production. More specifically, there is a rising demand for advanced polyesters displaying new functional properties while meeting higher sustainability criteria. Polyesters are part of everyday life with applications in clothing, food packaging, car manufacturing and biomedical devices. This reviewis intended to provide an overviewof the array of renewable building blocks already available for synthetic purposes and exploitable in the production of polyesters. Moreover, newgreener routes formore environmentally friendly polyester production and processing are discussed, pointing out the major technological challenges.Open Access mandate NO. https://www.openaire.eu/search/project?projectId=corda_______reservedmixedPellis, Alessandro; Herrero Acero, Enrique; Gardossi, Lucia; Ferrario, Valerio; Guebitz, GeorgPellis, Alessandro; Herrero Acero, Enrique; Gardossi, Lucia; Ferrario, Valerio; Guebitz, Geor

Enzyme-catalyzed functionalization of poly(L-lactic acid) for drug delivery applications

Polymer-based drug delivery systems are attracting interest for biomedical and, in particular, oncology-related applications due to interesting characteristics in terms of prolonged drug release. In this study, we investigated a new poly(lactic acid) (PLA)- based drug delivery system in which the cationic chemotherapeutic drug doxorubicin was adsorbed via ionic interactions. PLA, a polyester already widely used for biomedical applications due to its biocompatibility and quick assimilation, was initially activated by mild enzymatic surface hydrolysis with cutinase, generating new carboxylic and hydroxyl groups without affecting the bulk properties of the PLA. After the enzyme activation of PLA, the Mn remained almost unchanged, 182 kDa versus 188 kDa for untreated PLA measured by gel permeation chromatography. In contrast, chemical hydrolysis substantially degraded the PLA films as indicated by a decrease of Mn from 188 kDa to 18 kDa. Surface imaging using Scanning Electron Microscopy revealed an increase of granular porosity on the surface upon enzymatic activations while Atomic Force Microscopy showed an increase of the surface roughness from 50 to 170 nm. The hydrophilicity of the enzymatically activated films dramatically increased, as demonstrated by the decrease of the Water Contact Angle from 50\ub0 to less than 20\ub0. The negative charges generated on the PLA films was exploited for loading with positively charged doxorubicin; with increasing extent of enzymatic hydrolysis a higher amount of surface functional groups were generated. Desorption studies indicated that the release of doxorubicin from the PLA surface depended on the ionic strength of the medium, thus confirming the ionic nature of the interactions