对-氯代苯胺(PCA)在填充床生物反应器中的降解作用

以氯代苯胺(PCA)为选择基质,用驯化技术从降解对二氯苯(p-DCB)的富集培养物中得到了以同化PCA为唯一碳源和氮源的混合微生物。将这种固定在填充床反应器中的微生物用于PCA的降解作用研究中。在该反应器里,PCA的生物降解遵循Logistic方程q=q_max/(1+e^α-βU_v).由方程求出了主要的动力学常数,K_s(半速率常数)和q_max(最大比基质降解速率).于PCA降解的同时,释放氯离子到培养基中。在水力停留时间3h, 进水PCA浓度为360mg·L^-1情况下,基质的体积降解率达到125mg·L^-1·h^-1;基质的百分去除率为91%.     

Grapevine xylem response to fungi involved in trunk diseases

Grapevine trunk diseases (GTD), caused by a wide range of different fungi, are responsible for decline and productivity losses in vines at all growth stages. Grapevine responses to fungal attack include morphological and physiochemical defence mechanisms in the vascular system to reduce fungal infections. However, the extent to which these responses could control further spread by GTD‐fungi in the xylem vessels is poorly known. This study shows the formation of tyloses inside xylem vessels of diseased grapevines, as well as extracellular ligninolytic activities [lignin peroxidase, manganese peroxidase (MnP) and/or laccase] exhibited by some GTD‐fungi isolated here from symptomatic grapevines. In particular, Botryosphaeriaceae spp. and Phaeoacremonium minimum showed all three lignin‐degrading enzymatic activities. We also examined whether selected vine phenolic compounds, often located in the vascular system in response to fungal infection, could affect the lignin‐degrading activity from those GTD‐fungi as well as fungal colonisation. We found that phenolic compounds appeared to inhibit MnP activity, in addition to reducing fungal growth by causing anomalies in the hyphae morphology. Our results support that affected grapevines can initiate the tylosis formation in order to constrain fungi in the xylem vessels, while highlight the complementary action of the phenolic compounds to inhibit the fungi growth and colonisation. Phenolic compounds are therefore likely to have important role in alternative strategies for preventing trunk diseases.     

Maximizing microbial degradation of perchlorate using a genetic algorithm: Media optimization

Microbial communities are under constant influence of physical and chemical components in ecosystems. Shifts in conditions such as pH, temperature or carbon source concentration can translate into shifts in overall ecosystem functioning. These conditions can be manipulated in a laboratory setup using evolutionary computation methods such as genetic algorithms (GAs). In work described here, a GA methodology was successfully applied to define sets of environmental conditions for microbial enrichments and pure cultures to achieve maximum rates of perchlorate degradation. Over the course of 11 generations of optimization using a GA, we saw a statistically significant 16.45 and 16.76-fold increases in average perchlorate degradation rates by Dechlorosoma sp. strain KJ and Dechloromonas sp. strain Miss R, respectively. For two bacterial consortia, Pl6 and Cw3, 5.79 and 5.75-fold increases in average perchlorate degradation were noted. Comparison of zero-order kinetic rate constants for environmental conditions in GA-determined first and last generations of all bacterial cultures additionally showed marked increases.     

Biohydrogen generation by mesophilic anaerobic fermentation of microcrystalline cellulose

Sixteen batch experiments were performed to evaluate the stability, kinetics, and metabolic paths of heat-shocked digester (HSD) sludge that transforms microcrystalline cellulose into hydrogen. Highly reproducible kinetic and metabolic data confirmed that HSD sludge could stably convert microcrystalline cellulose to hydrogen and volatile fatty acids (VFA) and induce metabolic shift to produce alcohols. We concluded that clostridia predominated the hydrogen-producing bacteria in the HSD sludge. Throughout this study the hydrogen percentage in the headspace of the digesters was greater than 50% and no methanogenesis was observed. The results emphasize that hydrogen significantly inhibited the hydrogen-producing activity of sludge when initial microcrystalline cellulose concentrations exceeded 25.0 g/L. A further 25 batch experiments performed with full factorial design incorporating multivariate analysis suggested that the ability of the sludge to convert cellulose into hydrogen was influenced mainly by the ratio of initial cellulose concentration (So) to initial sludge density (Xo), but not by interaction between the variables. The hydrogen-producing activity depended highly on interaction of So x (So/Xo). Through response surface analysis it was found that a maximum hydrogen yield of 3.2 mmol/g cellulose occurred at So = 40 g/L and So/Xo = 8 g cellulose/g VSS. A high specific rate of 18 mmol/(g VSS-d) occurred at So = 28 g/L and So/Xo = 9 g cellulose/g VSS. These experimental results suggest that high hydrogen generation from cellulose was accompanied by low So/Xo.     

Determination of the enantiomeric purity of (−−) 2-(N-propyl-n-2-thienylethylamino)-5-hydroxytetralin (n-0923) by chiral stationary phase HPLC

The determination of the enantiomeric impurity, i.e., the percentage of (+) N?0437 (= N?0924) in several batches of (??) N-0437 (= N-0923) by chiral HPLC is described. Enantiomeric impurities were calculated based on the peak areas of the two baseline separated enantiomers in the chromatogram. The enantiomeric impurities found in different batches ranged from 0.02% to 0.11%. Calibration curves of the two isomers of N-0437 (Fig. 1,) were made twice to study the reproducibility and linearity of the method. The absorbance ratio, N-0923/N-0924, was found to be 1.02 with a relative standard deviation (RSD) of 9% over the whole concentration range used for the calibration curves.     

Stereoselective Degradation of Chiral Fungicide Myclobutanil in Rat Liver Microsomes

Myclobutanil, (RS)‐2‐(4‐chlorophenyl)‐2‐(1H‐1, 2, 4‐triazol‐1‐ylmethyl)hexanenitrile is a broad‐spectrum systemic triazole fungicide which consists of a pair of enantiomers. The stereoselective degradation of myclobutanil was investigated in rat liver microsomes. The concentrations of myclobutanil enantiomers were determined by high‐performance liquid chromatography (HPLC) with a cellulose‐tris‐(3,5‐dimethyl‐phenylcarbamate)‐based chiral stationary phase (CDMPC‐CSP) under reversed phase condition. The t_1/2 of (+)‐myclobutanil is 8.49 min, while the t_1/2 of (–)‐myclobutanil is 96.27 min. Such consequences clearly indicated that the degradation of myclobutanil in rat liver microsomes was stereoselective and the degradation rate of (+)‐myclobutanil was much faster than (–)‐myclobutanil. In addition, significant differences between two enantiomers were also observed in enzyme kinetic parameters. The V_max of (+)‐myclobutanil was about 4‐fold of (–)‐myclobutanil and the CL_int of (+)‐myclobutanil was three times as much as (–)‐myclobutanil after incubation in rat liver microsomes. Corresponding consequences may shed light on the environmental and ecological risk assessment for myclobutanil and may improve human health. Chirality 26:51–55, 2013. © 2013 Wiley Periodicals, Inc.     

Fermentative degradation of monohydroxybenzoates by defined syntrophic cocultures

From anaerobic freshwater enrichment cultures with 3-hydroxybenzoate as sole substrate, a slightly curved rod-shaped bacterium was isolated in coculture with Desulfovibrio vulgaris as hydrogen scavenger. The new isolate degraded only 3-hydroxybenzoate or benzoate, and depended on syntrophic cooperation with a hydrogenoxidizing methanogen or sulfate reducer. 3-Hydroxybenzoate was degraded via reductive dehydroxylation to benzoate. With 2-hydroxybenzoate (salicylate), short coccoid rods were enriched from anaerobic freshwater mud samples, and were isolated in defined coculture with D. vulgaris. This isolate also fermented 3-hydroxybenzoate or benzoate in obligate syntrophy with a hydrogen-oxidizing anaerobe. The new isolates were both Gram-negative, non-sporeforming strict anaerobes. They fermented hydroxybenzoate or benzoate to acetate, CO₂, and, presumably, hydrogen which was oxidized by the syntrophic partner organism. With hydroxybenzoates, but not with benzoate, Acetobacterium woodii could also serve as syntrophic partner. Other substrates such as sugars, alcohols, fatty or amino acids were not fermented. External electron acceptors such as sulfate, sulfite, nitrate, or fumarate were not reduced. In enrichment cultures with 4-hydroxybenzoate, decarboxylation to phenol was the initial step in degradation which finally led to acetate, methane and CO₂.     

呼伦贝尔典型退化草原土壤理化与微生物性状

以内蒙古克鲁伦河流域呼伦贝尔典型草原为对象,设置了轻度、中度和重度退化3种类型样地,研究不同程度退化草原的物种组成、地上生物量、土壤理化性状、土壤微生物数量和酶活性,以及微生物生物量的变化.结果表明: 中度退化样地的群落物种丰富度最大,轻度退化样地的地上生物量显著高于重度退化样地.退化样地的土壤水分、养分(有机质、全氮),微生物量碳、氮,以及微生物数量和酶活性显著下降,土壤容重显著增加.退化样地的土壤微生物生物量碳、氮在128～185和5.6～13.6 g·kg^-1,土壤脱氢酶和脲酶活性均与土壤容重呈显著负相关,与土壤全氮、有机质、微生物数量以及微生物生物量碳、氮呈显著正相关,地上生物量与土壤细菌和真菌数量呈不同程度的正相关.     

草原群落退化演替过程中微斑块土壤碳氮的空间异质动态

微斑块变化是草原退化过程中的活跃成分。分析了呼伦贝尔克氏针茅草原逆行演替过程中微斑块土壤全碳、全氮和碱解氮含量的空间异质性,提出了"养分聚集效应"的概念。研究结果表明:随着群落退化演替的加剧,土壤全碳、全氮和碱解氮的含量均表现为演替前期演替后期演替中期(P0.05)。从土壤全碳、全氮和碱解氮的变异系数和变异函数综合分析来看,10 cm×10 cm微尺度上,草原退化演替过程中土壤全碳、全氮和碱解氮的空间异质性具有明显的不一致性;全碳的空间异质性表现为演替中期演替前期演替后期,全氮表现为演替后期演替前期演替中期,碱解氮表现为演替中期演替后期演替前期。草原退化过程中土壤养分在微斑块上的富积和迁移表现出尺度依赖性和变异性。     

Interferon-γ activates the cleavage of double-stranded RNA by bovine seminal ribonuclease

Bovine seminal ribonuclease (BS-RNase), a dimeric homologue of RNase A, cleaves both single- and double-stranded RNA and inhibits the growth of tumor cells. Its catalytic activity against double-stranded RNA, either homopolymeric ([³H]polyA/polyU) or mixed sequence, is enhanced by bovine or human recombinant interferon-γ (IFN-γ). Activation is seen with as little as 4–10 interferon units per assay. Enhancing the degradation of double-stranded RNA, an intermediate in the growth cycle of many viruses, could contribute to IFN-γ's ability to control cell growth and induce an antiviral state.