Greg T. Lonergan

Preparation, surface modification and characterisation of solution cast starch PVA blended films

Several blends have been prepared of polyvinyl alcohol, starch and glycerol. The blend containing 20% polyvinyl alcohol has been modified by application of chitosan to the surface. The blend, and its modified form have been characterised by atomic force microscopy, x-ray diffraction, Fourier transform infra-red spectroscopy, contact angle measurements, 13C-NMR spectroscopy and scanning electron microscopy. The blended films were flexible and homogeneous on a macroscopic scale but on a microscopic scale there seemed to be small patches of individual components. Surface modification altered some of the characteristics of the film. The blends had surface roughness intermediate between that of the pure components. The addition of chitosan made the film more hydrophobic than the unmodified film but slightly less than the starch film. There was no evidence of new bond formation among the individual components. Solution casting reduced the overall crystallinity in the blended films.

Transformation and degradation of the disazo dye Chicago Sky Blue by a purified laccase from Pycnoporus cinnabarinus

The degradation of the disazo dye Chicago Sky Blue 6B by a purified laccase from Pycnoporus cinnabarinus was investigated. Laccase was purified to homogeneity and characterized. The enzyme had a molecular size of 63 kDa as determined by SDS-PAGE and an isoelectric point at pH 3. Amino acid composition and N-terminal amino acid sequence was shown to be similar to other fungal laccases. The purified laccase was stable for 1 h at 60 degrees C and was irreversibly inactivated by sodium azide at 0.1 mM. Laccase was shown to initiate destruction of the chromophore of the disazo dye Chicago Sky Blue, resulting in the formation of two intermediate products with absorption intensities about one order of magnitude lower than the parent molecule. The rate at which the dye was transformed by purified laccase was shown to increase with increasing concentrations of the enzyme.

Developing biodegradable mulch films from starch-based polymers

This paper examines the development of starch-based plastics for use as biodegradable mulch film. A variety of starch-based polymers are blended with high performance biodegradable polyester polymers in order to determine the applicability of films to be processed on a film blowing line and to perform well in mulch film field trials. The process of material formulation, film blowing processing and scale-up and performance properties are highlighted for a successful material. Insights into future developments of starch-derived biodegradable polymers are given.

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.

Laccase variation during dye decolourisation in a 200 L packed-bed bioreactor

SummaryThe white-rot fungus, Pycnoporus cinnabarinus, was grown in a 200 L packed-bed bioreactor. The dye, Remazol Brilliant Blue R, was added to the reactor and was rapidly decolourised. The phenoloxidase, laccase, catalysed this process. Laccases isolated from different days in the bioreactor cycle indicated variations in charge to size characteristics. Purified laccase from different days was isoelectrically focused and showed variations in intensities and numbers of bands whilst catalytic activity was retained.

Decolourisation of a pigment plant effluent by Pycnoporus cinnabarinus in a packed-bed bioreactor

SummaryThe decolourisation of wastewater from a pigment plant by the white-rot fungus Pycnoporus cinnabarinus was studied in a packed-bed bioreactor. Decolourisation was first observed 48 to 72 h after inoculation and was followed using UV/VIS spectrophotometry. An assessment of the inhibitory properties of the effluent on the growth of Pycnoporus cinnabarinus showed that this fungus can tolerate high levels of potentially toxic waste.

A biodegradable lethal ovitrap for control of container-breeding Aedes.

ABSTRACT Lethal ovitraps (LO) have been successfully deployed in dengue control operations in north Queensland, Australia since 2004. However, the current plastic-bucket LO must be retrieved before the pesticide-treated strip degrades and the trap begins producing mosquitoes. The logistics involved with trap retrieval are considerable and include recording trap location and retrieval date onto a database, locating and retrieving each trap, and examining lethal ovitraps for eggs. Collectively, these necessary activities greatly reduce the efficiency of dengue control. In response, we have developed a biodegradable lethal ovitrap (BLO) that does not need to be retrieved for the control of container-breeding Aedes, particularly Aedes aegypti. The BLOs were made by injection molding with the use of 2 proprietary blends of thermoplastic starch (TPS) polymer based on plasticised amylose maize polymers. In field trials, Ae. aegypti readily oviposited in BLOs, with those dyed black with the use of carbon black preferred. Water loss was higher in BLOs than in standard plastic LO because of weeping from the walls, although none of the BLOs failed in the 5 wk of the trial. The occurrence and rate of Ae. aegypti oviposition in both BLOs and the LO was comparable. In an accelerated standard composting trial (ISO16929:2002E), both BLOs fragmented within 4 wk, and no BLO particles were visible after 12 wk. Large numbers of BLOs could be deployed in a “set it—and forget it” strategy to control Ae. aegypti and to stop dengue transmission, and could be used in a community participation program to maximize coverage.

Mycelial fragment size distribution: an analysis based on fractal geometry

The use of white-rot fungi for biodegradative research and developmental application requires seeding with a suitable inoculum. This paper presents a new method for the quantitative analysis of a mycelial inoculum composed of homogenized hyphal fragments. Our method is premised on a power-law behaviour between frequency and the size of these mycelial fragments. It is shown that the fragment distribution profile can be determined by regression to give the fractal fragmentation dimension, D. The influence of homogenizer speed was also investigated over a range from 8333 rpm to 25 000 rpm, which corresponds to a shear rate range of 13.9 × 103 to 41.7 × 103 s−1. The highest D value was shown at a shear rate of 27.8 × 103 s−1 for 30 s, implying greatest homogeneity in the size distribution function over the measured range (0–500 μm2). As shear force and duration increases (up to a threshold value) the production of small fragments is facilitated with a corresponding decrease in the D value. The slope relation express the fragment diversity whereas the reciprocal fractal valie characterizes the distribution size probability. Image-analysis methodology is described and the implications of a fractal description of a mycelial inoculum are also considered.

Biodegradation and ecotoxicity evaluation of a bionolle and starch blend and its degradation products in compost

A polymer based on a blend of starch and Bionolle(TM) has been prepared and tested for biodegradation in compost. The polymer was completely mineralised to carbon dioxide in 45 days. The potential toxicity of the polymer was tested against the earthworm Eisenia fetida using a modification of the American Standard for Testing Materials E1976-97. The earthworms were exposed to 30 g of the polymer for 28 days and changes in weight recorded. In addition, the polymer was firstly degraded by the compost and the worms exposed to the breakdown products for 28 days. Differences in weight were also recorded. In each case the production of juveniles was noted and all earthworms were examined for pathology. The results obtained were processed statistically using a t-test. The number of juveniles, produced from the breakdown products, was highly significant (P < 0.001) when compared to the earthworms added to the intact polymer. There was a definitely significant difference (P < 0.01, t = 3.25) in change in weight between the earthworms that were exposed to the polymer directly and those that were exposed to the breakdown products. There was no indication of any pathology of any earthworms. The polymer is considered safe for this species

Laccase catalyzes formation of an indamine dye between 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid

Abstract Laccase from Coriolus hirsutus catalyzes the oxidative condensation reaction between 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid to form a blue indamine dye. Optimum enzyme activity in this reaction occurs at pH 5. The rate of formation of the dye is linear with time until an equilibrium is reached. The absorbance values at equilibrium depends on the concentration of reactants, although maximum absorbance at equilibrium is obtained at a final concentration of 2.0 · 10−3 m 3-dimethylaminobenzoic acid and 4.8 · 10−5 m 3-dimethyl-2-benzothiazolinone hydrazone in the reaction mixture. The laccase-catalyzed condensation occurs in the absence of hydrogen peroxide contrasting with the reaction in the presence of horseradish peroxidase. When laccase is present, pretreatment of solutions with catalase does not inhibit dye formation, whereas dye is not formed when peroxidase alone is present.