Microbial detoxification of metalaxyl in aquatic system

Four microorganisms, Pseudomonas sp. （ER2）, Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, were isolated from cucumber leaves previously treated with metalaxyl using enrichment technique. These isolates were evaluated for detoxification of metalaxyl at the recommended dose level in aquatic system. The effect of pH and temperature on the growth ability of the tested isolates was also investigated by measuring the intracellular protein and mycelia dry weight for bacterial and fungal isolates, respectively. Moreover, the toxicity of metalaxyl after 28 d of treatment with the tested isolates was evaluated to confirm the complete removal of any toxic materials （metalaxyl and its metabolites）. The results showed that the optimum degree pH for the growth of metalaxyl degrading isolates （bacterial and fungal isolates） was 7. The temperature 30℃ appeared to be the optimum degree for the growth of either fungal or bacterial isolates. The results showed that Pseudomonas sp. （ER2） was the most effective isolate in metalaxyl degradation followed by Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, respectively. There is no toxicity of metalaxyl detected in the supematant after 28 d of treatment with Pseudomonas sp. （ER2）. The results suggest that bioremediation by Pseudomonas sp. （ER2） isolate was considered to be effective method for detoxification of metalaxyl in aqueous media.     

New insights into different surfactants’ impacts on sludge fermentation: Focusing on the particular metabolic processes and microbial genetic traits

• The promoting effects for VFA generation follow the order of APG>SDBS>HTAB. • Surfactants improve the WAS solubilization/hydrolysis and acidification processes. • The VFA promotion is associated with surfactants’ distinctive characteristics. • Surfactants induce the enrichment of functional bacteria for VFA biosynthesis. • The vital genes for substrates delivery, metabolism, and VFA yields are upregulated. Surfactants were expected to exhibit positive effects on the waste activated sludge (WAS) disposal. However, the systematic comparison of different categories of surfactants on the WAS fermentation and the functional mechanisms, especially microbial metabolic traits, have not yet been precisely explored. This study revealed the positive effects of different surfactants on the volatile fatty acid (VFA) production, which followed the order of alkyl polysaccharides (APG)>sodium dodecylbenzene sulfonate (SDBS)>hexadecyl trimethyl ammonium bromide (HTAB). Mechanistic exploration found that the presence of different surfactants improved solubilization and hydrolysis steps, and then contributed to the subsequent acidification with different efficiencies. The functional microorganisms associated with VFA generation were enriched in surfactant-conditioned reactors. Metagenomic analysis further indicated that the key genes involved in the particular process of VFA generation were over-expressed. The simultaneous bioavailable substrate improvement, functional bacterial enrichment, and metabolic activity upregulation induced by different surfactants jointly contributed to VFA promotion during WAS fermentation. This study could provide a comprehensive realization of surfactants’ impacts on the WAS fermentation process, and more importantly, it reminded the public to discern the distinct interplaying effects induced by different chemicals in regulating the WAS disposal and resource recovery.     

Biodegradation of azo dyes by genetically engineered azoreductase

A azoreductase gene with 537 bp was obtained by PCR amplification from Rhodobacter sphaeroides ASI. 1737. The enzyme,with a molecular weight of 18.7 kD, was efficiently expressed in Escherichia coli and its biodegradation characteristics for azo dyes were investigated. Furthermore, the reaction kinetics and mechanism of azo dyes catalyzed by the genetically engineered azoreductase were studied in detail. The presence of a hydrazo-intermediate was identified, which provided a convincing evidence for the assumption that azo dyes were degraded via an incomplete reduction stage.     

高活性絮凝剂产生菌群的构建、培养及应用研究

从筛选到的絮凝剂产生菌中构建出能比单一菌群产生更高絮凝活性的复合菌群——复合菌群1（BAFRT4＋CYGS1）．为降低复合菌群1的培养成本,尝试用啤酒废水替代葡萄糖作为培养基中的碳源和能源并获得成功．在优化培养条件下,复合菌群1所产MBF的絮凝活性达96.8％．复合菌群1所产MBF对靛蓝印染废水有良好的处理效果,最大CODCr去除率和脱色率分别达79．2％和87．6％．     

高效水解酸化UASB活性污泥的菌群结构分析

采用454高通量测序技术对低能耗、低污泥产量且具有脱氮效能的印染废水处理工艺中UASB污泥的微生物菌群结构进行了分析.结果表明,UASB内污泥的微生物菌种呈多样性分布且优势菌群突出,通过菌群鉴定发现,脱硫橄榄样菌属(Desulfobacula)、Levilinea、长绳菌属(Longilinea)、Candidatus Tammella、Paludibacter、索氏菌属(Thauera)、Tepidimicrobium、杆状脱硫菌属(Desulforhabdus)、类芽孢杆菌属(Paenibacillus)、梭菌属(Clostridium)是主要的优势菌属.其中,梭菌属是起到产酸和污泥减量作用的主要菌种.另外,具有脱氮效能的原因可能是由于发生了硫酸盐型厌氧氨氧化作用.通过Shannon、Chao、Simpson、Shannon指数的计算,发现该UASB中微生物较其他废水处理系统,群落结构拥有较高的多样性和丰度,有利于稳定产酸.     

Photocatalytic bacterial inactivation by polyoxometalates

The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO₂ photocatalyst. Aqueous suspensions of the microorganisms (10⁷–10⁸ cfu ml⁻¹) and POM (or TiO₂) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO₂-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₄SiW₁₂O₄₀) tested in this study, the inactivation of E. coli was fastest with H₄SiW₁₂O₄₀ while that of B. subtilis was the most efficient with H₃PW₁₂O₄₀. Although the biocidal action of TiO₂ photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO₂-PCI. While TiO₂ caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO₂-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology.     

Influence of the zebra mussel and fish fry on structural and functional characteristics of microorganisms in experimental ecosystems

The interactions of zebra mussels, invertebrates, fish, and microorganisms were studied experimentally. Trends in the distribution of total bacterial biomass, the abundance of heterotrophic organisms, and their functional activities in water and grounds were analyzed. The most favorable conditions for development of bacteria developed in June, in the presence of fish and without zebra mussels. In experimental ecosystems with zebra mussels, a decrease in the abundance and activity of microorganisms and a change of dominant yeast forms were observed.     

根系分泌物与根际微生物相互作用研究综述

对几种主要根系分泌物与根际微生物之间的相互作用关系和影响机理的研究进行了综述，同时提出了今后在根系分泌物及根际微生态方面需要深入研究的几个问题。     

有机固体废物堆肥化处理的微生物学机理研究

由于符合持续发展的理念 ,利用微生物技术处理有机固体废物越来越受到人们的重视 ,其核心问题则是木质纤维素的生物降解。随着园林废物等高木质纤维素含量的城市生活垃圾的不断增加 ,以及对农业固体废物和食品工业废物再利用的需要 ,这一领域的研究取得了很大的进展。在研究中 ,针对好氧堆肥和厌氧发酵 2项主要的微生物处理技术 ,对其优势微生物菌群、不同降解底物和微生物降解动力学方面的最新研究进展进行了回顾和总结 ,并对环境微生物制剂的应用以及有机固体废物的微生物处理技术的发展做了合理的展望。     

复合微生物菌剂强化堆肥技术研究

采用复合微生物菌剂对生活垃圾的接种堆肥技术进行了实验研究。通过测定堆肥过程中反应器出口O2、CO2与H2S气体浓度及对堆肥样品扫描电镜照片分析，比较了3个接种组与1个对照组中堆料中微生物总数变化、种群结构演替及堆肥腐熟速度。试验结果表明，在原料成分为：生活垃圾／成熟堆肥=80／20，有机物约为60％，初始含水率为55％，初始C／N-30时，对于不同接种量的复合微生物接种系统堆料中分别接种0．2％、0．3％、0．5％(质量百分含量)，与加入0．3％灭活菌的对照组进行对比实验，接种复合微生物菌剂堆肥系统不仅微生物总数高于对照组，而且其种群结构合理，能明显提高堆肥效率，有效控制臭气的产生，提高堆肥腐熟度。