Petroleum exploitation enriches the sulfonamide resistance gene sul2 in off shore sediments

Antibiotic resistance genes(ARGs)have been considered as emerging contaminants in nature owing to their wide distribution and human health risk.Anthropogenic activities can increase the diversity and abundance of ARGs and promote their spread in environment.Offshore environment is affected by multiple types of anthropogenic activities,of which excessive accumulation of petroleum substances poses a serious threat.Our previous experimental study has demonstrated that petroleum can increase the abundance of sulfonamide resistance genes(SRGs)in the seawater through horizontal gene transfer.However,the influence of petroleum substances on SRGs in offshore environment,especially adjacent the petroleum exploitation platform,is still unclear.Therefore,the effect of offshore oil exploitation on SRGs was investigated in the surface sediments collected from the Liaodong Bay,north China.The genes of sul1 and sul2 were present in all of the collected samples,while the sul3 gene was not detected in any sediments.The absolute abundance of sul2 gene in each sample was higher than sul1 gene.Class 1 integrons enhanced the maintenance and propagation of sul1 gene but not sul2 gene.More importantly,the results indicate that the absolute abundance of sul2 gene present in the offshore sediments that affected by petroleum exploitation was significantly higher than those in control.These findings provided direct evidence that offshore oil exploitation can influence the propagation of SRGs and implied that a more comprehensive risk assessment of petroleum substances to public health risks should be conducted.

Coupled effects of methane monooxygenase and nitrogen source on growth and poly-β-hydroxybutyrate(PHB)production of Methylosinus trichosporium OB3b

The coupled effects of nitrogen source and methane monooxygenase（MMO） on the growth and poly-β-hydroxybutyrate（PHB） accumulation capacity of methanotrophs were explored.The ammonia-supplied methanotrophs expressing soluble MMO（s MMO） grew at the highest rate, while N2-fixing bacteria expressing particulate MMO（p MMO） grew at the lowest rate. Further study showed that more hydroxylamine and nitrite was formed by ammonia-supplied bacteria containing p MMO, which might cause their slightly lower growth rate. The highest PHB content（51.0%） was obtained under nitrogen-limiting conditions with the inoculation of nitrate-supplied bacteria containing p MMO. Ammoniasupplied bacteria also accumulated a higher content of PHB（45.2%） with the expression of p MMO, while N2-fixing bacteria containing p MMO only showed low PHB production capacity（32.1%）. The maximal PHB contents of bacteria expressing s MMO were low, with no significant change under different nitrogen source conditions. The low MMO activity,low cell growth rate and low PHB production capacity of methanotrophs continuously cultivated with N2 with the expression of p MMO were greatly improved in the cyclic NO3-N2 cultivation regime, indicating that long-term deficiency of nitrogen sources was detrimental to the activity of methanotrophs expressing pMMO.

Removal of nitric oxide from simulated flue gas via denitrification in a hollow-fiber membrane bioreactor

A hollow-fiber membrane bioreactor （HMBR） was studied for its ability to treat nitric oxide （NO） from simulated flue gas. The HMBR was operated for 9 months and showed a maximum elimination capacity of 702 mg NO/（m2.day） with a removal efficiency of 86% （gas residence time of 30 sec, inlet NO concentration of 2680 mg/m^3, pH 8）. Varying operation parameters were tested to determine the stability and response of the HMBR. Both the inlet NO concentration and gas residence time influenced the removal of NO in the HMBR. NO elimination capacity increased with an increase in inlet NO concentration or a shortening of gas residence time. Higher removal efficiency of NO was obtained at a longer gas residence time or a lower inlet NO concentration. Microbial communities of the HMBR were sensitive to the variation in pH value and alkalescence corresponding to an optimum pH value of 8. In addition, NO elimination capacity and removal efficiency were inversely proportional to the inlet oxygen concentration. Sulfur dioxide had no great influence on elimination capacity and removal efficiency of NO. Product analysis was performed to study N20 and N2 production and confirmed that the majority of the microorganisms were denitrifying bacteria in the HMBR. Compared to other bioreactors treating NO, this study showed that the denitrifying HMBR was a good option for the removal of NO.

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation （anammox） process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months.The average removal efficiencies of ammonia and nitrite were both over 80%,and the maximum total nitrogen removal rate of 1.85 kg N/（m^3 ·day） was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids （MLSS）/L.Scanning electron microscope （SEM） observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity,and the cell size was quite uniform.Transmission electron microscope photos showed that cells were round or oval,the cellular diameter was 0.6-1.0 μm,and the percentage of the anammoxosome compartment was 51%-85% of the whole cell volume.Fluorescence in situ hybridization analysis （FISH） indicated that anammox bacteria became the dominant population in the community （accounting for more than 51% of total bacteria on day 250）.Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp.,a new anammox species.In addition,the average effluent suspended solid （MLSS） concentrations of outlets I （above the non-woven carrier） and II （below the non-woven carrier） were 0.0009 and 0.0035 g/L,respectively.This showed that the non-woven carrier could catch the biomass effectively,which increased biomass and improved the nitrogen removal rate in the reactor.

Enrichments of methanotrophic–heterotrophic cultures with high poly-β-hydroxybutyrate(PHB) accumulation capacities

Methanotrophic–heterotrophic communities were selectively enriched from sewage sludge to obtain a mixed culture with high levels of poly-β-hydroxybutyrate（PHB）accumulation capacity from methane.Methane was used as the carbon source,N2as sole nitrogen source,and oxygen and Cu content were varied.Copper proved essential for PHB synthesis.All cultures enriched with Cu could accumulate high content of PHB（43.2%–45.9%）,while only small amounts of PHB were accumulated by cultures enriched without Cu（11.9%–17.5%）.Batch assays revealed that communities grown with Cu and a higher O2content synthesized more PHB,which had a wider optimal CH4：O2range and produced a high PHB content（48.7%）even though in the presence of N2.In all methanotrophic–heterotrophic communities,both methanotrophic and heterotrophic populations showed the ability to accumulate PHB.Although methane was added as the sole carbon source,heterotrophs dominated with abundances between 77.2%and 85.6%.All methanotrophs detected belonged to type II genera,which formed stable communities with heterotrophs of different PHB production capacities.

Sulfide-driven nitrous oxide recovery during the mixotrophic denitrification process

We propose a novel sulfide-driven process to recover N_(2)O during the traditional denitrification process.The optimum initial sulfide concentration was 120 mg/L,and the N_(2)O percentage in the gaseous products (N_(2)O+N_(2)) was up to 82.9%.Moreover,sulfide involved in denitrification processes could substitute for organic carbon as an electron donor,e.g.,1g sulfide was equivalent to 0.5-2 g COD when sulfide was oxidized to sulfur and sulfate.The accumulation of N_(2)O was mainly due to the inhibiting effect of sulfide on nitrous oxide reductase (N_(2)OR),which was induced by the supply insufficiency of electrons from cytochrome c (cyt c) to N_(2)OR.When the initial sulfide concentration was 120 mg/L,the N_(2)OR activity was only 36.8%of its original level.According to the results of cyclic voltammetry,circular dichroism spectra and fluorescence spectra,significant changes in the conformations and protein structures of cyt c were caused by sulfide,and cyt c completely lost its electron transport capacity.This study provides a new concept for N_(2)O recovery driven by sulfide in the denitrification process.In addition,the findings regarding the mechanism of the inhibition of N_(2)OR activity have important implications both for reducing emissions of N_(2)O and recovering N_(2)O in the sulfide-driven denitrification process.

Biodegradation of indole by a newly isolated Cupriavidus sp. SHE

Indole, a typical nitrogen heterocyclic aromatic pollutant, is extensively spread in industrial wastewater. Microbial degradation has been proven to be a feasible approach to remove indole, whereas the microbial resources are fairly limited. A bacterial strain designated as SHE was isolated and found to be an efficient indole degrader. It was identified as Cupriavidus sp. according to 16 SrRNA gene analysis. Strain SHE could utilize indole as the sole carbon source and almost completely degrade 100 mg/L of indole within 24 hr. It still harbored relatively high indole degradation capacity within p H 4–9 and temperature 25°C–35°C. Experiments also showed that some heavy metals such as Mn2＋, Pb2＋and Co2＋did not pose severe inhibition on indole degradation. Based on high performance liquid chromatography–mass spectrum analysis, isatin was identified as a minor intermediate during the process of indole biodegradation. A major yellow product with m/z 265.0605（C15H8N2O3） was generated and accumulated, suggesting a novel indole conversion pathway existed. Genome analysis of strain SHE indicated that there existed a rich set of oxidoreductases, which might be the key reason for the efficient degradation of indole. The robust degradation ability of strain SHE makes it a promising candidate for the treatment of indole containing wastewater.

Biosynthesis of gold nanoparticles by Trichoderma sp.WL-Go for azo dyes decolorization

Developing an eco-friendly approach for metallic nanoparticles synthesis is important in current nanotechnology research. In this study, green synthesis of gold nanoparticles （AuNPs） was carried out by a newly isolated strain Trichoderrna sp. WL-Go. UV-vis spectra of AuNPs showed a surface plasmon resonance peak at 550 nm, and transmission electron microscopy images revealed that the AuNPs were of varied shape with well dispersibility. The optimal conditions for AuNPs synthesis were HAuC14 1.0 mmol/L, biomass 0.5 g and pH 7-11. Moreover, the bio-AuNPs could efficiently catalyze the decolorization of various azo dyes. This research provided a new microbial resource candidate for green synthesis of AuNPs and demonstrated the potential application ofbio-AuNPs for azo dye decolorization.

Enhanced bio-decolorization of1-amino-4-bromoanthraquinone-2-sulfonic acid by Sphingomonas xenophaga with nutrient amendment

Bacterial decolorization of anthraquinone dye intermediates is a slow process under aerobic conditions. To speed up the process, in the present study, effects of various nutrients on 1-amino-4-bromoanthraquinone-2-sulfonic acid（ABAS） decolorization by Sphingomonas xenophaga QYY were investigated. The results showed that peptone, yeast extract and casamino acid amendments promoted ABAS bio-decolorization. In particular,the addition of peptone and casamino acids could improve the decolorization activity of strain QYY. Further experiments showed that L-proline had a more significant accelerating effect on ABAS decolorization compared with other amino acids. L-Proline not only supported cell growth, but also significantly increased the decolorization activity of strain QYY. Membrane proteins of strain QYY exhibited ABAS decolorization activities in the presence of L-proline or reduced nicotinamide adenine dinucleotide, while this behavior was not observed in the presence of other amino acids. Moreover, the positive correlation between L-proline concentration and the decolorization activity of membrane proteins was observed, indicating that L-proline plays an important role in ABAS decolorization. The above findings provide us not only a novel insight into bacterial ABAS decolorization, but also an L-proline-supplemented bioaugmentation strategy for enhancing ABAS bio-decolorization.

Multistep conversion of cresols by phenol hydroxylase and 2,3-dihydroxy-biphenyl 1,2-dioxygenase

A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the first time. Docking studies displayed by PyMOL predicted that cresols and methylcatechols could be theoretically transformed by this multistep conversion system~ High performance liquid chromatography mass spectrometry （HPLC-MS） analysis also indicated that the products formed from multistep conversion were the corresponding 3-methylcatechol, 4-methylcatechol, 2- hydroxy-3-methyl-6-oxohexa-2,4-dienoic acid （2- hydroxy-3-methyl-ODA） and 2-hydroxy-5-methyl-6-oxo- hexa-2,4-dienoic acid （2-hydroxy-5-methyl-ODA）. The optimal cell concentrations of the recombinant E. coli strain BL21 （DE3） expressing phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） and pH for the multistep conversion of o- and m-cresol were 4.0 （g-L-1 cell dry weight） and pH 8.0, respectively. For the first step conversion, the formation rate of 3- methylcatechol （0.29μmol·L-1·min-1·mg-1cell dry weight） from o-cresol was similarly with that ofmethylca- techols （0.28 μmol·L-1·min-1·mg-1 cell dry weight） from m-cresol by strain PHrND. For the second step conversion, strain BphCLA_4 showed higher formation rate （0.83 μmol·L-1·min-1·mg-1 cell dry weight） for 2-hydroxy-3-methyl- ODA and 2-hydroxy-5-methyl-ODA from m-cresol, which was 1.1-fold higher than that for 2-hydroxy-3-methyl- ODA （0.77 μmol·L-1·min-1·mg-1. mglcell dry weight） from ocresol. The present study suggested the potential application of the multistep conversion system for the production of chemical synthons and high-value products.

A novel sequence batch membrane carbonation photobioreactor developed for microalgae cultivation

In this study,a novel sequence batch membrane carbonation photobioreactor was developed for microalgae cultivation.Herein,membrane module was endowed functions as microalgae retention and CO2 carbonation.The results in the batch experiments expressed that the relatively optimal pore size of membranes was 30 nm,photosynthetically active radiation was 36 W/m^2 and the CO2 concentration was 10%(v/v).In long-term cultivation,the microalgal concentration separately accumulated up to 1179.0 mg/L and 1296.4 mg/L in two periods.The concentrations of chlorophyll a,chlorophyll b and carotenoids were increased about 23.2,14.9 and 6.3 mg/L respectively in period I;meanwhile,the accumulation was about 25.0,14.5,6.6 mg/L respectively in the periodⅡ.Furthermore,the pH was kept about 5.5-7.5 due to intermittent carbonation mode,which was suitable for the growth of microalgae.Transmembrane pressure(TMP)was only increased by 0.19 and 0.16 bar in the end of periodsⅠandⅡ,respectively.The pure flux recovered to 75%-80%of the original value by only hydraulic cleaning.Scanning electron microscope images also illustrated that carbonation through membrane module could mitigate fouling levels greatly.

Reductive transformation of p-nitrotoluene by a new iron-fly ash packing

A new iron-fly ash packing was studied for reductive transformation of p-nitrotoluene. The packing was made of iron, fly ash and kaolin with the mass ratio of 36：7：2. A reactor was designed to investigate the long-term performance of the packing. The results showed that the reduction of p-nitrotoluene increased with decreasing pH, because the reduction potential of reaction increased with the concentration of H＋. The pH was one of the key factors impacting the reductive transformation of p-nitrotoluene. Comparing iron-activated carbon packing with the new iron-fly ash packing, the reduction efficiencies were respectively 76.61% and 75.36% after20 days. The reduction efficiency for both was around 50% at 40 days. It was evident that these two kinds of packing had no significant difference in their capability for p-nitrotoluene reductive transformation. Compared with iron-activated carbon, the new iron-fly ash packing had obvious advantages in terms of manufacturing costs and environmental pollution degradation. This study showed that the new iron-fly ash packing had good performance in reductive transformation of nitrotoluene compounds.

Selection of microalgae for high CO_2 fixation efficiency and lipid accumulation from ten Chlorella strains using municipal wastewater

As significant differences in cellular physiology, metabolic potential and genetics occur among strains with morphological similarity, the screening of appropriate microalgae species for effective CO2 fixation and biodiesel production is extremely critical. In this study, ten strains of Chlorella were cultivated in municipal wastewater influent（MWI） and their tolerance for MWI, CO2 fixation efficiency and lipid productivity were assessed. The results showed that the biomass concentrations of four strains（Chlorella vulgaris, Chlorella64.01, Chlorella regularis var. minima and Chlorella sp.） were significantly higher than other strains. When the cultivation systems were aerated with 10% CO2, Chlorella sp. showed the highest CO2 fixation efficiency（35.51%）, while the highest lipid accumulation（58.48%） was observed with C. vulgaris. Scanning electron microscopy images revealed that the cells of both Chlorella sp. and C. vulgaris kept their normal morphologies after 15 day batch culture.These findings indicated that Chlorella sp. and C. vulgaris have fairly good tolerance for MWI,and moreover, Chlorella sp. was appropriate for CO2 fixation while C. vulgaris represented the highest potential for producing biodiesel.