Anaerobic microbial degradation of poly (3-hydroxyalkanoates) with various terminal electron acceptors

The microbial degradation of poly (3-hydroxyalkanoates) (PHAs) under anaerobic conditions with various terminal electron acceptors was examined. Nitrate-reducing consortia were established using activated sludge, and PHAs were shown to be biodegradable under these conditions. A positive correlation between carbon dioxide production and nitrate reduction was demonstrated. Nitrous oxide accumulated as the main N-containing product of nitrate reduction. The amount of PHAs in activated sludge cultures decreased approximately 20% within 40 days of incubation. Attempts were made to establish iron- and sulfate-reducing consortia from spring water, yet it could not be demonstrated that the mixed cultures were capable of degrading PHAs. Pure cultures of iron- and sulfate-reducing bacteria could not utilize PHAs as sole carbon sources. Methanogenic environments sampled included pond sediment and rumen fluid. PHAs were fermented to methane and carbon dioxide after 10 weeks by a sediment consortium, with 43 to 57% of the substrate carbon transformed to methane. Although it could not be demonstrated that PHAs were biodegraded by a rumen fluid consortium, a facultative anaerobic bacterium, identified as aStaphylococcus sp., that could grow on PHAs was isolated from rumen fluid.     

苯酚降解菌Y_1的分离与鉴定

旨在从微生物降解的角度出发,解决苯酚大量应用带来的含酚废水对环境污染问题.采用富集培养、驯化筛选和平板划线等方法,从某化工厂废水中分离得到4株苯酚降解菌.利用4-氨基吡啉分光光度法测定其苯酚降解能力,筛选出降解率较高的菌株Y_1.经形态学观察、生理生化鉴定和16S rDNA序列分析,将该菌初步鉴定为苏云金芽孢杆菌(Ba...     

Contribution to the Study of Fungal Attack on Some Plasticized Vinyl Formulations

The objective of this study was to develop new vinyl flooring formulations with increased resistance to fungi and microorganisms attack, by using plasticizers having a chemical composition different from that of common di-ethylhexyl phthalate (DOP). It is suspected that during the vinyl flooring life service, the attack of fungi and microorganisms leads to the degradation of DOP and the release of some volatile organic compounds (VOC). For this reason the new materials were formulated with plasticizers having chemical composition different of that of DOP i.e.: diethyleneglycol dibenzoate (2–45), tricresyl phosphate (Lindol) and phenol alkylsulphonic ester (Mesamoll). For the same reason in the new flooring formulations the vinyl polymer, vinyl chloride-vinyl acetate copolymer (VC-VAc), was partially replaced with lignin (L) a natural polymer and major component of wood and vascular plants. Besides its other functions in wood, L imparts resistance to the most microorganisms attack. An organosolv lignin Alcell lignin (AL) was utilized as partial replacement of VC-VAc copolymer.The influence of the new plasticizers, as well as the influence of the partial replacement of VC-VAc copolymer with L on the resistance of the new formulations to fungal attack was evaluated following a standard procedure given in ASTM G 21–2002 “Determining Resistance of Synthetic Polymeric Materials to Fungi”. The evaluation has been undertaken for controls (formulated without AL) and blends (formulated with 20 parts AL) specimens. Test specimens were inoculated with a mixture of five fungi. Following 28 days of incubation at 28°C and 95% relative humidity, the specimens were examinated visual and under the microscope and rated for fungal growth. Weight loss, changes in mechanical properties and changes in glass transition temperature due to the effect of biodeterioration were also determined.Although each plasticizer has a specific resistance to hydrolysis due to differences among ester groups, the visible effects of fungal attack, in formulations without AL, is similar for all plasticized controls, with the exception of formulations incorporating diethyleneglycol dibenzoate (2–45) in which a higher degree of biodegradation was always present. Based on the weight loss of specimens formulated without AL, their resistance to fungal attack can be rated as follows: . The same rating is applicable for blend specimens. The results have demonstrated that each particular AL-plasticizer-additives formulation has its specific mechanism of biodegradation.     

β-Cyclodextrin and its derivatives-enhanced solubility and biodegradation of 2-nitrobiphenyl

This paper investigated the effects of β-cyclodextrins (β-CD) and its two derivatives, hydroxypropyl-β-cyclodextrin (HPCD) and carboxymethyl-β-cyclodextrin (CMCD), on the solubility and biodegradation of 2-nitrophenyl by aa Acinetbacter sp.Results showed that β-CD ,HPCD and CMCD could not be utilized by Acinetbacter sp. as sole carbon source and none of the CDs had toxic effects on the growth of the bacteria in the experiments; all the CDs could enhance the apparent solubility and accelerate the biodegradation of 2-nitrobipheny. It showed that biodegradation-accelerating effects of CDs on 2-nitrobiphenyl were correlated with their solubility-enhancing effects. Among three CDs investigated,CMCD had the most obvious effects both on the apparent solubility and the biodegradation, followed by β-CD and HPCD.     

Biodegradable water-soluble polycarboxylic acid design: Biodegradability and builder performance in detergent formulation of partially dicarboxylated polyuronide containing sugar residues in the backbone

Partially dicarboxylated polyuronide having a variable amount of unreacted sugar blocks as an enzymatically cleavable segment was prepared by the controlled oxidation of pectic acid and alginic acid. It was found that partially dicarboxylated polyuronides containing uronide blocks showed better biodegradability than those having no uronide block in the polycarboxylate chain. The rate of biodegradation varies according to the degree of dicarboxylation. It was confirmed that dicarboxy polyuronides containing more than 70% unreacted uronide residues tended to biodegrade quickly. The biodegradability obtained by the BOD test and the enzymatic degradability are well correlated, suggesting that these polymers are first cleaved at the sugar blocks by carbohydrase with subsequent assimilation of the resultant oligomeric fractions. Detergency was dependent on the content of the carboxylate groups in the polymer. The polymers with high carboxylate contents showed better builder performance. The detergency of dicarboxy pectic acid was better than that of dicarboxy alginic acid when compared on the basis of an equal degree of dicarboxylation.     

Stimulated Biodegradation of Crude Oil in Soil Amended with Periwinkle Shells

The potential of periwinkle shell (PS) in enhancing the microbial break down of crude oil spilled in soil were studied. The results revealed that the counts of crude oil degrading bacteria in oil-polluted soil fortified with PS were higher than the counts in unfortified soil. The rates and total extent of crude oil biodegradation in the soil were stimulated by the amendment. About 43.4 percent of crude oil was degraded in unfortified soil after 16 days as compared to 70.1 percent oil biodegradation, which occurred in PS fortified soil during the same period. These values were significantly (P>0.05) different from each other. Amendment of the soil with PS also raised the pH of the soil from acidic to alkaline range. The crude oil degrading microorganisms identified in PS amended soil were of the genus Pseudomonas, Bacillus, Micrococcus, Acinetobacter, Penicillium, Aspergillus, Mucor and Rhizopus. Similarly, Pseudomonas, Bacillus, Micrococcus, Mucor, Aspergillus and Penicillium were identified as crude oil degrading microorganisms in unamended soil. The bacteria formed either stable or unstable emulsions, suggesting that the organisms produce surface-active agents (biosurfactants) during the biodegradation process. The results of this study indicate that PS can be used in reclaiming oil-polluted soil.     

Kinetic Study of Naphthalene Biodegradation in Aerobic Slurry Phase Microcosms for the Optimisation of the Process

The research was focused on the slurry-phase biodegradation of naphthalene. The biodegradation process was optimised with preliminary experiments in slurry aerobic microcosms. From soil samples collected on a contaminated site, a Pseudomonas putida strain, called M8, capable to degrade naphthalene was selected. Microcosms were prepared with M8 strain by mixing non-contaminated soil and mineral M9 medium. Different experimental conditions were tested varying naphthalene concentration, soil:water ratio and inoculum density. The disappearance of hydrocarbon, the production of carbon dioxide, and the ratio of total heterotrophic and naphthalene-degrading bacteria were monitored at different incubation times. The kinetic equation that best fitted the disappearance of contaminant with time was determined. The results showed that the isolated strain enhanced the biodegradation rate with respect to the natural biodegradation.     

苯酚降解菌CM-HZX1菌株的分离、鉴定及降解性能研究

从污水处理厂的活性污泥中分离出一株以苯酚为唯一碳源生长的高效降解苯酚菌CM-HZX1.通过形态特征、生理生化及16S r DNA基因序列分析,初步鉴定菌株属于红球菌(Rhodococcus sp.),16S r DNA在Gene Bank的登录号为KM014567.实验结果表明,菌株CM-HZX1培养及降解苯酚的最适条件为p H=7.0,温度30℃,转速为150 r·min~(-1).该菌株能耐受4%的盐度,适应性强.0.5 g·L~(-1)苯酚在24 h时的降解率可达93.6%,1.5 g·L~(-1)苯酚在48 h时的降解率在90%以上.研究表明,该菌株在处理工业含酚废水方面具有广阔的应用前景.     

蜡状芽胞杆菌对芘的降解特性及降解酶研究

考察蜡状芽胞杆菌(Bacillus cereus)对水体中芘的降解特性,分析其代谢产物和降解酶的活性.结果表明,1 mg·L-1Mn2+、0.1 mg·L-1Fe3+和10 mg·L-1葡萄糖混合物对芘的降解有明显促进作用;1 g·L-1菌体在120 h内对2.5μmol·L-1芘的降解率达到61.4%.利用LC-MS/MS分析芘代谢产物,检测到1-萘酚、2-萘酚、9-羟基菲和1-羟基芘4种单羟基多环芳烃,表明芘在单加氧酶作用下开环降解,且B.cereus能有效分解利用4种代谢产物,其最高利用率分别为100%、90.3%、98.3%和52.7%.酶活力分析实验结果表明,B.cereus具有的水杨酸羟化酶,邻苯二酚1,2-双加氧酶和邻苯二酚2,3-双加氧酶在芘的降解中起关键作用,其酶活力经芘诱导后均有明显提高.结合产物分析及酶活测定,推断B.cereus对芘的降解途径以及降解过程是由单加氧酶和双加氧酶联合起作用.     

电化学氧化与生物法联合降解木质素

为开发经济和环境安全的木质素降解技术,采用ECO-BD(electrochemical oxidation and biodegradation, 电化学氧化与生物降解)工艺联合降解木质素,以Ti/Sn-SbO₂电极为阳极,无水Na₂SO₄为电解质,在恒电流条件下,应用响应面法得到ECO-BD联合降解木质素的最佳电化学条件:电流密度为8.64 mA/cm2,电量为20.00 kC,c(Na₂SO₄)为0.15 mol/L. 在该条件下,ECO-BD对1 g/L木质素溶液的COD_Cr去除率为59.31%,单位能耗为28.87 kW·h/kg. 采用傅里叶变换红外光谱及气相色谱-质谱对ECO-BD联合降解木质素过程中的降解产物进行分析发现,ECO能有效地破坏木质素的酚羟基结构及发色基团,木质素多聚体的醚键先被断裂形成单体,随后芳环结构被氧化生成醌类化合物,再进一步开环和裂解生成小分子酸类或被矿化成CO₂和H₂O;电解后溶液生化可降解性由0.20~0.25升至0.31~0.37,缩短了后续生物降解时间. 研究显示,ECO能先行打断抵御微生物攻击的木质素顽固键合结构,有利于后续BD消除残余碎片,实现木质素的ECO-BD高效低成本降解.