New enzymes with potential for PET surface modification

This work describes newly isolated organisms and their potential to modify the surface of polyethylene terephthalate (PET). Out of the different screening processes, four bacterial and five fungal strains were isolated. A PET model substrate was synthesized (bis (benzoyloxyethyl) terephthalate) and used in the screening process, mimicking the polymer in its crucial properties and having the advantage of defined hydrolysis products. On this model substrate, extracellular enzyme preparations from the isolated microorganisms showed a maximum activity of 8.54 nkat/L. All enzyme preparations showed esterase activity on p-nitrophenyl-acetate while no activity was found on p-nitrophenyl decanoate or p-nitrophenyl palmitate. Increased hydrophilicity of PET fabrics after enzyme treatment was found based on rising height and water dissipation measurements

Crystallization of the extracellular rubber oxygenase RoxA from Xanthomonas sp. Strain 35Y

Rubber oxygenase A (RoxA) from Xanthomonas sp. strain 35Y is an extracellular dioxygenase that is capable of cleaving the double bonds of poly(cis-1,4-isoprene) into short-chain isoprene units with 12-oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD) as the major cleavage product. Crystals of the dihaem c-type cytochrome RoxA were grown by sitting-drop vapour diffusion using polyethylene glycol as a precipitant. RoxA crystallized in space group P2(1), with unit-cell parameters a = 72.4, b = 97.1, c = 101.1 A, beta = 98.39 degrees, resulting in two monomers per asymmetric unit. Diffraction data were collected to a limiting resolution of 1.8 A. Despite a protein weight of 74.1 kDa and only two iron sites per monomer, phasing was successfully carried out by multiple-wavelength anomalous dispersion

Purification and properties of a poly (beta-hydroxybutyrate) depolymerase from penicillium sp.

An extracellular poly (β-hydroxybutyrate) (PHB) depolymerase was purified from a Penicillium sp. DS9701-09a by centrifugation, ultrafiltration, precipitation and gel filtration chromatography. The specific activity of the purified enzyme was 37.9-folds higher than that of the culture supernatant and the recovery yield was 11.8%. The PHB deploymerase molecular mass was 44.8 kDa from analysis of both Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometer. The isoelectric point of 6.7 for the enzyme was determined by a two-dimensional electrophoresis. The optimum enzyme activity was observed at a temperature of 50 °C and pH 5.0. The apparent K m of the enzyme was found to be 1.35 mg/mL. The PHB depolymerase consisted of 16 kinds of normal amino acids. The secondary structure of the enzyme was determined by CD spectrum. α-helix and β-turn were found to be 66% and 34% for the enzyme without ammonium sulphite. Chemical inhibition on the PHB depolymerase activity was examined and EDTA was found to have a significantly inhibitory effect.Hongyu Liu, Hu Zhang, Shan Chen, Dongbo Liu and Hongmei Xi

From numbers to ecosystems and biodiversity: A mechanistic approach to monitoring

Diverse political, cultural and biological needs epitomise the contrasting demands impacting on the mandate of the South African National Parks (SANParks) to maintain biological diversity. Systems-based approaches and strategic adaptive management (learn by doing) enable SANParks to accommodate these demands. However, such a management strategy creates new information needs, which require an appropriate analytical approach. We use conceptual links between objectives, indicators, mechanisms and modulators to identify key concerns in the context of and related to management objectives. Although our suggested monitoring designs are based mostly on defined or predicted underlying mechanisms of a concern, SANParks requires inventory monitoring to evaluate its key mandate. We therefore propose a predictive inventory approach based on species assemblages related to habitat preferences. Inventories alone may not always adequately serve unpacking of mechanisms: in some cases population size needs to be estimated to meet the information needs of management strategies, but actual population sizes may indirectly affect how the species impact on other values. In addition, ecosystem objectives require multivariate assessments of key communities, which can be used in trend analysis. SANParks therefore needs to know how to detect and define trends efficiently, which, in turn, requires precision of measures of variables. Conservation implications: Current research needs with regard to monitoring should focus on defining designs to yield optimal precision whilst taking methodology, survey trade-offs and analytical approaches into account. Use of these directives and research will guide monitoring during evaluation of SANParks objectives at various scales