Biodegradation of Electrospun Poly-(ɛ-caprolactone) Non-woven Fabrics by Pure-Cultured Soil Filamentous Fungi

The biodegradation of electrospun nano-fibers of poly(-caprolactone) (PCL) was initially investigated with respect to the environmental application of PCL non-woven fabrics, using pure-cultured soil filamentous fungi, Aspergillus oryzae, Penicillium caseicolum, P. citrinum, Mucor sp., Rhizopus sp., Curvularia sp., and Cladosporium sp. Three kinds of non-woven PCL fabrics with different mean fiber diameters (330, 360, and 510 nm) were prepared by changing the viscosities of the pre-spun PCL solutions (150, 210, and 310 cPs, respectively). All of the pure-line soil filamentous fungi tested grew on the two fiber materials. Electron microscopy was used to observe the biodegradation processes revealing remarkable growth of two fungi, Rhizopus sp. and Mucor sp., along with the accompanying collapse of the nano-fiber matrices. In the biochemical oxygen demand (BOD) test, the biodegradation of the 330 nm PCL nano-fibers by Rhizopus sp. and Mucor sp. exceeded 20 and 30% carbon dioxide generation, respectively. The biodegradability of the PCL non-woven fabrics decreased with the mean fiber diameter and the 330 nm PCL nano-fiber that was made from 150 cPs solution (concentration, 7 wt%) exhibited the highest biodegradability. These results might offer some clues for the applications of the PCL non-woven fabrics having the controlled biodegradability in the environmental uses.     

Impact of microbial activity on the hydraulic properties of fractured chalk

The impact of microbial activity on fractured chalk transmissivity was investigated on a laboratory scale. Long-term experiments were conducted on six fractured chalk cores (20 cm diameter, 23-44 cm long) containing a single natural fracture embedded in a porous matrix. Biodegradation experiments were conducted under various conditions, including several substrate and oxygen concentrations and flow rates. 2,4,6-Tribromophenol (TBP) was used as a model contaminant (substrate). TBP biodegradation efficiency depended mainly on the amount of oxygen. However, under constant oxygen concentration at the core inlet, elevating the flow rates increased the removal rate of TBP. Transmissivity reduction was clearly related to TBP removal rate, following an initial slow decline and a further sharp decrease with time. The fracture's transmissivity was reduced by as much as 97% relative to the initial value, with no leveling off of the clogging process. For the most extreme cases, reductions of 262 and 157 microm in the equivalent hydraulic apertures were recorded for fractures with initial apertures of 495 and 207 microm, respectively. The reductions in fracture transmissivity occurred primarily because of clogging by bacterial cells and extracellular polymeric substances (EPS) produced by the bacteria. Most of the biodegradation activity was concentrated near the fracture inlet, where the most suitable biodegradation conditions (nutrients and oxygen) prevailed, suggesting that the clogging had occurred in that vicinity. The clogging must have changed the structure of the fracture void, thereby reducing the active volume participating in flow and transport processes. This phenomenon caused accelerated transport of non-reactive tracers and doubled the fracture's dispersivity under constant flow rates.     

Mineralization of Poly(ɛ-caprolactone)/Adipate Modified Starch Blend in Agricultural Soil

The biodegradability properties of poly(ɛ-caprolactone) (PCL) and modified adipate-starch (AS) blends, using Edenol-3203 (E) as a starch plasticizer, were investigated in laboratory by burial tests of the samples in previously analyzed agricultural soil. The biodegradation process was carried out using the respirometric test according to ASTM D 5988-96, and the mineralization was followed by both variables such as carbon dioxide evolution and mass loss. The results indicated that the presence of AS-E accelerated the biodegradation rate as expected.     

Biodegradability of a Selected Range of Polymers and Polymer Blends and Standard Methods for Assessment of Biodegradation

Synthetic polymers are important to the packaging industry but their use raises aesthetic and environmental concerns, particularly with regard to solid waste accumulation problems and the threat to wildlife. Some concerns are addressed by attention to problems associated with source reduction, incineration, recycling and landfill. Others are addressed by the development of new biodegradable polymers either alone or in blends. Materials used for biodegradable polymers include various forms of starch and products derived from it, biopolyesters and some synthetic polymers. Starch is rapidly metabolised and is an excellent base material for polymer blends or for infill of more environmentally inert polymers where it is metabolised to leave less residual polymer on biodegradation. This should help to improve the environmental impact of waste disposal. A number of standard methods have been developed to estimate the extent of biodegradability of polymers under various conditions and with a variety of organisms. They tend to be used mainly in the countries where they were developed but there is much overlap between the standards of different countries and wide scope for development of consistent and international standards.     

Estimation on Biodegradability of Poly (3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate) (PHB/V) and Numbers of Aerobic PHB/V Degrading Microorganisms in Different Natural Environments

To assess the capacity of the natural environment for degrading PHB/V, the film-MPN method proposed previously was modified to estimate the numbers of PHB/V degrading microorganisms (degraders) in various environments. The First-Order Reaction (FOR) model was used to determine the appropriate incubation period for the method. Numbers of aerobic PHB/V degraders were estimated in garden soil, paddy field soil, farm soil, river bank soil, infertile garden soil, river water, activated sludge, and seawater by the film-MPN method. Results were compared with those estimated by the clear-zone technique and showed that the film-MPN method was suitable for estimating the numbers of PHB/V degraders in the environments tested. On the other hand, biodegradability of injection molded PHB/V samples was investigated in several kinds of environments. The changes of weight were studied and results showed that biodegradability of PHB/V related to the numbers of PHB/V degraders in similar ecosystem in different regions. In different environments the biodegradability of PHB/V not only related to the number of PHB/V degraders, but also depended on whether there were conditions for the PHB/V degraders to grow and proliferate easily in the environment.     

The biodegradation of lactic acid-based poly(ester-urethanes)

The biodegradability of lactic acid based poly(ester-urethanes) was studied using the headspace test method, which was performed at several elevated temperatures. The poly(ester-urethanes) were prepared using a straight two-step lactic acid polymerization process. The lactic acid is first condensation polymerized to a low molecular weight hydroxyl-terminated telechelic prepolymer and then the molecular weight is increased with a chain extender such as diisocyanate. In the biodegradation studies the effect of different stereostructures (different amounts of D-units in the polymer chain), the length of ester units, and the effect of crosslinking on the biodegradation rate were studied. The results indicate that poly(ester-urethanes) do not biodegrade at 25‡C, but at elevated temperatures they biodegrade well. The different stereostructures and crosslinking have a strong influence on the biodegradation rate. The length of ester units in the polymer chain also affects the biodegradation rate, but much less than crosslinking and stereostructure.     

黄河水中细菌对18种酚的降解作用研究

为了掌握酚污染物在黄河水中的生物降解情况,采用苯酚为唯一碳源的液体培养基富集黄河水中的降酚微生物,并研究富集微生物对18种酚的降解作用.结果表明:黄河水中含有降解苯酚的微生物,该微生物属于细菌;降酚细菌对实验用的15种酚均有降解能力,其中对二元酚分解能力较强;但是,对4-氨基苯酚、2,4,6-三氯苯酚、五氯苯酚无分解能力;混合细菌的降酚能力可以代表黄河水体的降酚能力.     

微生物降解油田含油污泥中烃类污染物的研究

微生物法治理油污土壤具有成本低、效果好的特点。其原理是微生物利用油烃作为碳源合成自身物质．进行生长繁殖，从而使油烃含量减少。在好氧和厌氧条件下，从油污土壤中分离纯化出4株能降解石油烃类的微生物CH1、CH2、CH3和CH4。经鉴定菌株CH3为假单胞菌属，通过生理特性实验，确定了其生长的最适pH值为7.5，油泥中石油烃类的降解率达85％。按照文中微生物处理舍油污泥的现场施工方案，可使处理后舍油污泥中烃类含量〈1500mg／kg（符合国标GB4284—1984要求）。     

含氟有机化合物优势降解菌的筛选

从受含氟有机物长期污染的污泥中驯化筛选得到7株优势降解菌，可利用氟代有机化合物为唯一大风大浪原生长。取其中2株菌进行生物忍耐力及生物降解实验，结果表明：菌株对经过台化的有机物有较强的忍受能力，在浓度高达1000mg/L的条件下仍能生长，全氟辛酸可被筛选菌脱氟降解。     

喹啉及其衍生物微生物降解研究进展

喹啉类氮杂环化合物在水、土壤环境中普遍存在，受其污染的水、土壤环境生物修复是目前环境治理领域的重要课题。介绍了近年来喹啉类氮杂环化合物微生物降解的国内外研究进展，主要包括可利用喹啉类氮杂环化合物作为碳源、氮源和能源的微生物资源、微生物降解的有氧代谢和无氧代谢两大途径，以及喹啉类化合物的降解动力学。在此基础上，提出了需要进一步研究的方向。