Production, Purification and Activity of an Extracellular Depolymerase from Aspergillus fumigatus

A strain of Aspergillus fumigatus, which was observed to rapidly degrade poly-3-hydroxybutyrate (PHB) in a leaf compost, was found to secrete an extracellular hydrolase when grown on PHB as the sole carbon source. Isolation and characterization of the PHB hydrolase (depolymerase) from this fungus revealed that the enzyme had a molecular weight of 57 kDa, an isoelectric point of 7.2, and a PHB hydrolysis activity maxima which occurred at 70°C and pH 8.0. Affinity labeling experiments suggested that this fungal hydrolase is a type of serine esterase. The cyclic trimers of 3-hydroxybutyrate were found to reversibly inhibit the enzymes.     

Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation

Three high molecular weight (120,000 to 200,000 g mol^–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M _w) was in the range of 50,000 to 75,000 g mol^–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M _w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.     

Integrated catchment management in Western Australia: Transition from concept to implementation

Integrated catchment management (ICM) was introduced as state policy in 1988 to overcome land and water degradation in Western Australia (WA). Key elements of ICM are cooperation among state and local governments and landholders; involvement of landholders and local communities in identification of issues and solutions; and, agreement on common objectives. This study identifies the issues that led to the adoption of integrated catchment management in Western Australia, outlines its main characteristics, and reviews the progress and problems encountered during its initial implementation. ICM has generally been accepted and endorsed in WA. However, differences of opinion have emerged regarding exactly what it means and how it should be applied. Designing ideal organizational structures for ICM is not sufficient for it to be effective. Ultimately, people have to make ICM function, and therefore it is essential that priority be given to cultivating the good will and trust necessary for ICM to work well. ICM also requires a long-term perspective and appreciation that it requires many people and agencies to move out of current “comfort zones.” As a result, initial implementation of ICM usually will encounter turbulence and debate.     

Comparative differences in Ontario farmers' environmental attitudes

This paper provides an analysis of a 1991 survey of the views of a stratified random sample of 1,105 Ontario farmers. Factor analysis, Kruskal—Wallis one-way ANOVA, chi-square and correlations were used to identify differences in farmers' attitudes toward rural environmental issues as a function of their demographic and farm characteristics. Younger, well-educated farmers, especially if female, were most concerned about the seriousness of rural environmental degradation. The largest operators expressed the greatest support for the use of agricultural chemicals, were most opposed to government conservation regulations and were least environmentally oriented. Such differences between Australian and Ontario farmers as the former's greater cautiousness about governmental regulation and receptivity to the Green Movement are a function of differing demographic and farm characteristics between Australia and Ontario.     

A respirometric method to measure mineralization of polymeric materials in a matured compost environment

A respirometric method was developed to measure the mineralization of polymeric materials in a matured compost environment. For the purpose of evaluating the method, results obtained for the mineralization of glucose and cellulose are presented. The matured compost, in addition to supplied nutrients, micronutrients, and an inoculum, serves as the matrix which supports the microbial activity. Recovery of the substrate carbon in the form of carbon dioxide from the glucose and cellulose added to test vessels was 68 and 70%, respectively. A statistical evaluation of the results obtained on substrate mineralization was carried out and showed acceptable reproducibility between replicate test vessels and test runs. The testing protocol developed has the following important characteristics: (1) the test reactors are maintained at 53 °C at a high solids loading (60% moisture), which has certain characteristics that are similar to a thermophilic compost environment; (2) the test matrix providing microbial activity is derived from readily available organic materials to facilitate reproducibility of the method in different laboratories; (3) the equipment required to perform this test is relatively inexpensive; and (4) the information obtained on polymer mineralization is vital to the study and development of biodegradable polymeric materials.Guest Editor: Dr. Graham Swift, Rohm & Haas.     

A study of the oxidative degradation of polyolefins

The oxidative degradation of polyolefins in the presence of transition metal catalysts is well known in the patent and technical literature. It has been suggested that a properly designed oxidatively degradable polymer could be used in limited lifetime articles and also on those whose primary method of disposal is composting, wherein the thermal activity is used to accelerate the oxidation process. The results of a detailed study of transition metal reactivity in the presence of numerous oxidation promoting species in polyolefins are presented. The oxidative degradation of these polyolefins was demonstrated at moderate temperatures under air and in a simulated compost environment. Approaches to determining the ultimate fate of these materials are discussed.     

Microtox assay to determine the toxicity of degradation products from degradable plastics

Six types of starch-polyethylene degradable plastics were evaluated for the release of water-soluble toxic compounds under accelerated degradation conditions. A plastic strip (2.5×15.2 cm) was placed in a 250-ml Erlenmeyer flask with 100 ml of ASTM type I water with or without trace element solutions and shaken at 65°C and 110 rpm for 20 weeks in replicates of two. High temperature was used to accelerate the oxidative degradation of polyethylene. Plastic degradation was measured by loss of tensile strength, percentage elongation, strain energy, and weight-average molecular weight. The most rapid period of polyethylene thermal degradation was complete for most materials by day 28. Ten-milliliter aqueous samples were removed from each flask at days 1, 7, 28, 56, 84, and 140 (water volumes were maintained at 100 ml with fresh type I water), filtered through glass filters, then evaluated by using the Microtox Toxicity Analyzer (Microbics Corporation, Carlsbad, CA). No water-soluble toxic compounds were detected during the period of rapid film degradation. Toxicity was observed at day 28 for one film and at day 84 for all films, which could possibly correlate with the release of small oxidative compounds such as formaldehyde and acetaldehyde. Because of the sensitivity of this assay, positive results must be confirmed by otherin vitro studies.Journal Paper No. J-14851 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Projects No. 2889 and 0178.     

电催化氧化技术处理含盐有机废水研究进展

介绍了电催化氧化技术在实际工业废水处理中的优势,对其反应原理进行了概述。总结了电催化氧化技术在石油、制药、造纸行业废水和含氨氮类有机废水处理中的研究进展,指出：电催化氧化技术未来的主要研究方向为研发新型电催化阳极材料;开发高效电解反应器;探索电催化氧化技术与其他处理工艺组合联用。     

光催化法降解有机废水的显著性研究

本文采用紫外光照射并加入催化剂的方法，对有机废水一阳离子艳红染料(5GN)进行了光催化降解的研究。从实际应用出发，实验得出了影响阳离子艳红染料降解的各因素的最佳取值及影响显著性次序。     

应用聚丙烯酰胺的环境与生态行为研究

聚丙烯酰胺(PAM)在油田中的大量使用,其环境和生态行为及降解产物对环境的潜在危害,都亟待去研究。本文分析论述了其物理、化学性质及化学降解、机械降解、热降解、生物降解性,及影响其在土壤中的被吸附的因素和生态毒理学研究,提出有待进一步研究的课题为:PAM在油藏条件下的降解机理和降解速度;PAM及其衍生物在环境中的存在形式及其迁移转化的方式,在生物体内的存在形式及其在生物圈内的迁移转化等。