查看更多>>摘要：The development of phototrophic biofilms deteriorating stone cultural heritage is a well-known phenomenon that causes not only discoloration but also micro-decohesion of substrates. Recently, essential oils (EOs) have resulted as successful natural biocides to be used for the restoration of cultural heritage as an alternative to chemicals. In a first experiment EOs of Lavandula angustifolia Mill. and Thymus vulgaris L. at 5% concentration were tested against cyanobacterial biofilms. Moreover, to develop a suitable protocol for in situ application, diverse concentrations (0.5% - 0.25% - 0.1%) of T. vulgaris EO were encapsulated within an alginate hydrogel and applied for different times on cyanobacterial biofilms. Chemical profiles of the two EOs were investigated via GC-MS, to identify the main plant compounds underlying the biocidal effects. Results showed that T. vulgaris EO, rich in thymol, had the greatest inhibitory effect of photosynthetic efficiency compared to essential oil of L. angustifolia, especially if suspended into hydrogel. The development of such innovative protocol allowed the concentration of the tested essential oil to be 0.1% (v/v), maintaining antimicrobial efficacy against cyanobacteria and reducing the volatility of the terpene components. This innovative method will facilitate the application also on vertical surfaces and the removal of the biofilm.
查看更多>>摘要：In crude oil transmission pipelines, some parts of the system receive minimal or no fluid flow ('dead legs'), which can on occasion lead to under deposit corrosion wherein a mixture of sediments, hydrocarbons, water, and microorganisms collectively contribute to an integrity failure. However, the microbial contribution to this phenomenon in crude oil transmission pipelines is poorly characterized. To better understand this process, we used a multiple lines of evidence approach to examine a dead leg failure event using sludge samples collected from at andnear the leak location and from non-corroded areas on the same pipe segment. Chemical analyses revealed elevated levels of acetate, total iron, and FeCO3 at the leak locations compared to non-corroded areas. Electrochemical techniques showed increased evidence for corrosion in leak site samples compared to noncorroded samples, while corrosion coupon analysis revealed many localized pits of up to 20 mu m deep in leak location samples compared to fewer pits that were up to 4 mu m deep from the non-corroded sample after incubating the samples for 30 days. 16S rRNA gene analysis revealed sulfide-producers, acetogens, and methanogens in all collected samples. The lack of detection of FeS as a corrosion product, no significant differences in sulfate and sulfide concentrations across all samples, and elevated levels of acetate at the leak location suggested that acetogens and/or fermentative bacteria contributed to this pipeline leak. This study highlights the use of a multiple lines of evidence approach that can be used to garner evidence to determine the contribution of MIC to failures in dead leg pipeline segments.
查看更多>>摘要：Plasmids disseminate pollutant-catabolic genes through horizontal transfer and contribute to the catabolic potential of the host microbial community. Genetic bioaugmentation of conjugative catabolic plasmids has recently been considered an effective and novel approach for long-term bioremediation of contaminated sites. In this study, we engineered an IncP-1 beta-2 subgroup plasmid pDCA-1 from Achromobacter sp. ANB-1 for its potential application in genetic bioaugmentation. A dcaA1A2B cluster responsible for the deamination of chloroaniline to chlorocatechol and a 1,2-dioxygenase gene (ccdC) for the ring cleavage of chlorocatechol were found to locate on the broad host range plasmid pDCA-1. Insertion of an amidase gene (phh or tccA2) at the accessory region of plasmid pDCA-1 greatly expanded its catabolic substrate spectrum from chloroaniline (3-chloroaniline and 3,4dichloroaniline) to herbicides (linuron, propanil, propham, and chlorpropham), bacteriostatic agent (triclocarban), plant regulator (forchlorfenuron), and insecticide (diflubenzuron). Taking advantages of highthroughput cell sorting and 16S rRNA gene-based amplicon sequencing, we depicted the diversity of bacterial recipients for the engineered plasmid pDCA-1-gfp-phh in a soil bacterial consortium, showing an excellent conjugative transfer capacity of the pDCA-1 derivative to various Gram negative and even positive strains in natural environment. All in all, the engineered plasmid pDCA-1 had a great potential in genetic bioaugmentation of the sites contaminated with chloroanilines and their derivatives.
查看更多>>摘要：The stimulation of growth by the addition of indigo carmine (5, 5 indigo disulfonic acid sodium salt, IC) was studied in the white-rot fungus Cyathus bulleri. C. bulleri was grown on a variety of solid medium and addition of IC (5000 mg/L) resulted in enhancement of growth, particularly on malt-extract agar. Stimulation of growth by IC was also observed in liquid cultures grown in potato dextrose broth. IC was degraded into anthranilic acid by oxidoreductases, particularly laccases, present in the culture broth of the fungus grown on wheat bran and orange peelings, which was confirmed by treatment of IC with purified laccase. Anthranilic acid was proposed to further enter into the tryptophan (TRP) biosynthetic pathway, as demonstrated by up-regulation of newly identified trpD, trpC and trp1 genes from this fungus. These genes encode anthranilate phosphoribosyl transferase, a multi-functional enzyme with phosphoribosyl anthranilate isomerase/other activities and tryptophan synthase respectively. No such increased transcription of these genes was observed in the absence of IC.
Logan, MohanakrishnanTan, Lea ChuaLens, Piet N. L.
10页
查看更多>>摘要：The energy potential of dissolved air floatation (DAF) slurry, a lipid-rich waste, is largely disregarded with the common practice of land spreading or landfilling. On the other hand, selenium (Se) contaminated wastewaters are perceived as unsuitable feedstocks because of their toxicity. This study aimed to evaluate the anaerobic co-digestion performance of a DAF slurry with Se rich wastewater using anaerobic granular sludge and waste activated sludge as the inocula. Anaerobic batch assays of DAF slurry supplemented with 0.05, 0.10, 0.25 and 0.50 mM selenate (SeO42-) and selenite (SeO32-), along with a control (without Se) were performed at 30 ?. Methanogenesis of the DAF slurry using anaerobic granular sludge was realised during co-digestion up to 0.50 mM SeO42-, whereas SeO32- was already toxic from 0.05 mM onwards. Co-digestion of the DAF slurry with 0.05 and 0.10 mM Se oxyanions (both selenate and selenite) containing wastewater using waste activated sludge achieved a similar cumulative methane yield of about 180 mL/g COD as that of mono-digestion (Se free DAF slurry) after 65 days of incubation. Simultaneously, more than 90% removal of Se was accomplished. The lag phase duration was, however, extended by 50 and 90% in the presence of 0.05 and 0.10 mM Se, respectively. The half maximal inhibitory concentration (IC50) for methane production using waste activated sludge was 0.08 mM for SeO42- and 0.07 mM for SeO32-. The IC50 amounted to 2.10 mM for SeO42- and 0.08 mM for SeO32-& nbsp;with anaerobic granular sludge. SeO42- and SeO32-& nbsp;were reduced to elemental Se nanoparticles, as shown by transmission electron microscopy. This study indicates the feasibility of methane production from a DAF slurry, codigested with wastewaters containing up to 0.10 mM SeO42- or SeO32-& nbsp;.
查看更多>>摘要：The effectiveness of an oxidative biomimetic copper-pyridine system (Cu-py-H2O2) was successfully demonstrated on model textile samples of unaged and artificially aged desized cotton inoculated with pure cultures of selected fungi, isolated from historical textile objects (Bjerkandera adusta (Basidiomycota), Cladosporium sp., Chaetomium cochlioides, Aspergillus conicus, and A. montevidensis (Ascomycota)). Colour, structure and mechanical properties of test cotton samples were evaluated. Investigation into bleaching effect against intra- and extracellular fungal pigments, and the influence on textile substrate revealed the 3-day treatment as the most appropriate length of bleaching procedure (bleaching achieved L*>90, a*<1, b*<10). The treatment had some undesirable effects on the structure and properties of the textile fabrics (cuticle flaking, longitudinal cracks, etc.), with mechanical (tensile) properties loss of maximum 60% (specific stress). The undesirable effects differed between test samples, with the least observed in control, uninoculated samples, moderate in samples, inoculated with the strains belonging to the selected ascomycetes, and the highest in the samples inoculated by selected basidiomycete (known to degrade cellulose). This is promising, as the Ascomycota are the fungi that usually cause the most intensive colouration of the textiles. Further optimization of the process may therefore lead to discolouration of the fungal stains with tolerable damage to underlaying textile.
查看更多>>摘要：In the past several years, products and methods alternative to conventional biocides, used in the conservation of cultural heritage objects, have been investigated increasingly to eradicate or prevent the growth of microorganisms and lichens on stone artworks. Although some concerns about conventional biocides are legitimate, the "run" to alternative substances is growing concern as well. This review aims at contributing to the interpretation of recent findings in innovative methods and substances focusing on i) resistance of biofilms to environmental stressors, including antimicrobials; ii) metals and metal-based compounds including nanoparticles; iii) mixtures of metal nanoparticles and metal oxides with water repellents and consolidants; iv) natural compounds (essential oils of plants, secondary metabolites of lichens, microbial by-products, microorganisms, extracts from marine organisms); v) toxicity of essential oils; vi) alternative chemicals (Ionic liquids, dimethyl sulfoxide gel, hydrolase enzymes). This review also includes a discussion on the advantages, drawbacks and limitations of the examined studies to encourage a constructive discussion among professionals involved in the field of stone heritage conservation, and to develop a sustainable path for managing the biological colonization. This state-of-the-art review indicates that further research is needed to propose alternative compounds to conventional biocides.
查看更多>>摘要：Biological denitrification is suppressed when temperature is lower than 10 degrees C. In this study, Psychrobacter cryohalolentis F5-6 was isolated from Harbin region and showed high aerobic-denitrifying rate at low temperature. It contained high percentage of unsaturated fatty acids (87.32%) and short chain saturated acid (3.4% C10:0 and 4.0% C12:0 3-OH). Acetate was the best carbon source for the strain F5-6 performing denitrification. Aerobic denitrification (napA gene) and nitrate assimilation (nasA gene) were the nitrate metabolism processes for the strain F5-6. Its biological nitrate removal (BNR) rate at 10 degrees C showed fit with Monod equation (R2 = 0.9808). The maximum BNR rate was 23.71 mg NO3- -N g- 1DW h-1 and KS was 116.96 mg L-1. The optimal denitrifying condition was pH 7.5, 15 degrees C with shaking speed of 180 rpm and C/N of 2. Results of this study supplied a bacterial resource for improving nitrate removal from low C/N water at low temperature.
NSTL
Elsevier