Bioremediation of hydrocarbons contaminated waters and soils: monitoring by luminescent bacteria test

Bioremediation has proven successful in numerous applications to petroleum hydrocarbons or chlorinated aromatic hydrocarbons contaminated soils. There is increasing interest in application of biotoxicity tests for ecological assessment and for supporting management decisions for remediation. Luminescent assays, light-emitting bacteria in particular, can be a suitable tool for environmental analysis, and in vivo luminescence is a rapid and precise indicator of the toxic effects of xenobiotic on micro-organisms. In this study, three different strains of marine bioluminescent bacteria have been employed to follow the changes in biotoxicity occurring during the laboratory scale bioremediation of water and soil samples contaminated by hydrocarbons and collected at an industrial area. The degradation was made by hydrocarbons degrading bacteria, both of commercial sources and isolated from polluted water and soils. The samples were treated for 45 days. The toxicity of the samples, before and after the bioremediation, was determined directly on water samples or on the extracts of soil samples. The yield of extraction by different solvents (acetone, dioxane, ethanol and dichloromethane) was evaluated by the bioluminescent test. The measurements were carried out using a microplate format both for short time of contact (60?minutes, acute toxicity) and for longer time intervals (24 hours, chronic toxicity). The results have been expressed as percentage of inhibition with respect to the blank emission (100% emission). Original and treated samples have been analysed by gas chromatography to assess the hydrocarbons (C?>?12 and Poly Chlorinated Biphenyls, PCB) content. The autochthonous bacteria isolated from polluted samples proved less effective, due to the short time for selection in remediation activity with respect to the commercial ones, but their capacity to degrade long chain hydrocarbons was satisfactory. The presented laboratory study can be applied also in case of on-field conditions.     

Layer‐by‐Layer Assemblies of Montmorillonite and Bacterial Cytochromes for Bioelectrocatalytic Devices

Clay‐based layer‐by‐layer architectures are studied in view of the development of new electrode materials for two highly attractive enzymatic reactions: metal bioremediation and hydrogen uptake. The buildup of layer‐by‐layer (LBL) assemblies of positively charged specific mediators of these enzymatic reactions and negatively charged montmorillonite nanoparticles were carried out onto gold and graphite electrodes. The structure and stability of the assemblies were examined using quartz crystal microgravimetry (QCM) and electrochemical techniques. Satisfactory catalytic efficiencies were observed through the LBL construction, either for bacterial cytochrome c₃‐mediated metal reduction, or hydrogen uptake via immobilized hydrogenase in the presence of an artificial shuttle, methylviologen. Interestingly, it is established that intercalating cytochrome c₃ layers between hydrogenase/montmorillonite layers not only protects hydrogenase from leaching, but allows H₂ uptake/evolution catalytic reaction without any additional diffusing redox mediator.     

海洋微生物研究的回顾与展望

报道了本课题组近年来基于新理念、新技术在海洋污染环境的微生物修复、海洋赤潮灾害的微生物调控、海洋微生物对海域生物生产力的调控、海洋微生物资源的保护与利用等研究方面的新成果；介绍了微生态制剂在海水养殖中的应用和海洋极端环境微生物研究的新趋势；展示了海洋中的微小生物对地球的巨大贡献．强调进一步开展海洋微生物研究的重要性、必要性、可行性和紧迫性．     

用喷泉式生物膜反应器去除养鱼水体中的氮素

介绍了一种用于净化养鱼水体的喷泉式生物膜反应器．首先在清洁的水中放养金鱼,考察水中氮素和COD浓度的增长规律．随后分别采用简单曝气和加入喷泉式生物膜反应器2种方法对水质进行净化,并比较他们的效果．结果表明：简单曝气可以降低NH4＋-N浓度,但不能有效去除总氮（TN）,而采用喷泉式生物膜反应器则可以有效地降低TN．通过TN去除动力学的分析,TN去除速率随着初始浓度的增加而增加,表现为Monod模型．其中C／N比对TN去除速率有明显影响,C／N比由5：1提高到15：1时,相应的TN去除速率（rmax）和饱和常数（Ks）分别提高了32％和降低了21％．     

粪产碱杆菌对富营养化景观水体水质改善能力的研究

在室内采用投菌法,利用粪产碱杆菌(Alcaligenes faecalis)对富营养化景观水体进行处理试验研究,通过不同的投菌量0.05‰、0.1‰、0.2‰,对水体进行处理.结果表明,粪产碱杆菌对富营养化水体中的总氮(TN)、总磷(TP)均有一定的去除效果,其中在投菌量为0.1‰时处理效果较好.通过进一步的连续投菌净化试验,水体中的TN、TP显著降低,处理后,藻类基本得到控制.由此可见,粪产碱杆菌能够有效地去除水体中的氮、磷,具有净化富营养化水体的作用.     

响应曲面法优化混合菌KW8-2修复石油污染土壤

采用响应曲面法优化混合菌KW8-2修复石油污染土壤的条件。以初始原油质量分数、接种量、氮磷比和表面活性剂用量为自变量,修复60 d的原油降解率为因变量,采用Box-Behnken(BB)设计,研究各自变量及其交互作用对污染土壤生物修复的影响,得到二次多项式回归方程预测模型。结果表明:原油质量分数分别为10×10-3、30×10-3和50×10-3的污染土壤,最佳修复条件下的原油降解率分别为67.12%、63.39%和56.57%,远高于单因素试验的最高值(63.78%、60.36%和55.44%);试验数据可为混合菌KW8-2修复原油污染实际土壤提供技术支持。     

粗砂-砾石海滩溢油污染的现场生物修复

在天津港六号码头的粗砂-砾石海滩进行了人工模拟溢油条件下的生物修复现场实验,考察了添加水溶性肥料、添加缓释肥料以及同时添加缓释肥料和石油烃降解菌等修复措施的有效性.结果表明,在120,d的修复时间内,同时添加缓释肥料和石油烃降解菌的体系石油烃生物降解常数（ks）最高,达0.007,2,d-1,为对照体系的2.4倍,该体系中氮、磷浓度和石油烃降解菌数量在较长时间内都维持较高水平,表明接种的石油烃降解菌能够直接利用缓释肥料所释放出来的营养元素而快速生长繁殖;添加水溶性肥料的体系短期内氮、磷含量显著提高,石油烃降解菌密度明显增大,石油烃降解速率加快,ks为对照试验池的1.8倍;而添加缓释肥料的体系氮、磷含量尽管明显高于对照体系,ks却略低于对照体系,这可能是由于土著微生物无法直接利用缓释肥料所释放的营养元素,甚至其释放的尿素在局部形成高氨氮环境而抑制微生物的生长.     

Definitive Screening Design and Artificial Neural Network for Modeling a Rapid Biodegradation of Date Palm Fronds by a New Trichoderma sp. PWN6 into Citric Acid

Generally, the bioconversion of lignocellulolytics into a new biomolecule is carried out through two or more steps. The current study used one-step bioprocessing of date palm fronds (DPF) into citric acid as a natural product, using a pioneer strain of Trichoderma harzianum (PWN6) that has been selected from six tested isolates based on the highest organic acid (OA) productivity (195.41 µmol/g), with the lowest amount of the released glucose. Trichoderma sp. PWN6 was morphologically and molecularly identified, and the GenBank accession number was MW78912.1. Both definitive screening design (DSD) and artificial neural network (ANN) were applied, for the first time, for modeling the bioconversion process of DPF. Although both models are capable of making accurate predictions, the ANN model outperforms the DSD model in terms of OA production, as ANN is characterized by a higher value of R² (0.963) and validation R² (0.967), and lower values of the RMSE (13.44), MDA (11.06), and SSE (9749.5). Citric acid was the only identified OA as was confirmed by GC-MS and UPLC, with a total of 1.5%. In conclusion, DPF together with T. harzianum PWN6 is considered an excellent new combination for citric acid biosynthesis, after modeling with artificial intelligence procedure.     

Enzymatic degradation of trichloroethylene using enzyme extracts isolated from a bacterial consortium

Degradation of trichloroethylene (TCE) using crude enzyme extracts from a bacterial consortium was examined for wastewater treatment. The effects of pH, chemical induction, and cofactor were investigate. Enzyme extracts showed an optimal activity (3.03±0.03 mg of TCE/[mg of protein·d]) at neutral pH (6.5–7.5). In an attempt to increase the production of effective enzymes for TCE degradation, chemical induction using both toluene and TCE in the growth of the bacterium consortium was conducted. Although the induction increased the overall production of protein by about fourfold, the activity of the extracts was only slightly improved (up to 3.40 mg of TCE/[mg of protein·d]), indicating that the induction did not specifically enhance the production of TCE-degrading enzymes. Interestingly, the addition of a cofactor (up to 0.02 mg/mL), NADH, led to an initial reaction rate of 5.30±0.05 mg of TCE/(mg of protein·d). This observation demonstrated that the availability of the cofactor played an important role in determining the overall degradation reaction rates. The observations with NADH were in agreement with the assumption that toluene monooxygenases (which are NADH dependent) are the key enzymes for the degradation reactions.     

Environmental biotechnology: a tandem of biocatalytic and engineering approaches

The review gives examples of integrated approaches based on a tandem of biocatalytic and engineering methods to problems in the biotechnological protection of three basic constituents of the environment, namely, soil, water, and atmosphere, from dangerous pollution. The current situation associated with oil pollution of soils and water surfaces in Russia is analyzed. The results of the field tests of the biopreparation Roder recently developed for bioremediation of these surfaces are presented. New solutions aiming at extending the area of application of high-rate anaerobic wastewater treatment at low temperatures (4—10 °C) are discussed. The efficiency of a novel anaerobic-aerobic hybrid reactor for mineralization of recalcitrant wastewater containing azo dyes was estimated. The last two lines relate to a traditional function of the environmental biotechnology (so-called end of pipe treatment). A biocatalytic technology for the removal of hydrogen sulfide and the recovery of elementary sulfur from contaminated gases was proposed. This highlights a new phase in the development of environmental biotechnology allowing waste recycling.