Characterization and analysis of petrochemical wastewater through particle size distribution, biodegradability, and chemical composition

The centralized treatment method is a widely used form of wastewater treatment that tends to be less effective at removing toxic substances. Therefore, a detailed analysis of the composition of wastewater can provide important information for the design of an effective wastewater treatment process. The objective of this paper was to investigate particle size distribution(PSD), biodegradability, and the chemical composition of the petrochemical wastewater discharges. For this purpose, this project selected the petrochemical wastewater and treated wastewater of China National Offshore Oil Corporation Zhongjie Petrochemical Co, Ltd. as the analysis objects.The step-by-step filtration method, along with a molecular weight classification method, was selected to build the chemical oxygen demand(COD) and biochemical oxygen demand(BOD) fingerprints of petrochemical wastewater and treated wastewater. The results showed that the main pollutants were settleable particles in petrochemical wastewater, which contributed to over 54.85% of the total COD. The colloidal particles with particle sizes in the range of 450–1000 nm had the highest COD value in the treated wastewater, which contributed34.17% of the total COD of treated wastewater. The results of the BOD analysis showed that the soluble fractions were the main reason that treated wastewaters did not meet the treatment standards. Tests on the organic compounds in petrochemical wastewater found that there were mainly linear paraffins, branched paraffins, benzene series compounds, and some plasticizers in the influent of the petrochemical wastewater. The most abundant pollutants in treated petrochemical wastewater were the adjacent diisobutyl phthalate and the linear alkanes.Fourier transform infrared(FTIR) transmission spectroscopy analysis showed that the settleable particles of petrochemical wastewater and membrane bioreactor(MBR)-treated wastewater contained multiple types of organic substances. The results also indicated that removing the oil-settleable substances, the colloidal particles(450–1000 nm), and the soluble organics will be necessary for the treatment of petrochemical wastewater.

n-Hexadecane and pyrene biodegradation and metabolization by Rhodococcus sp. T1 isolated from oil contaminated soil

The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. T1 was isolated from oil contaminated soil. Strain T1 could remove 90.81% n-hexadecane(2 vol%) and 42.79% pyrene(200 mg·L^(-1)) as a single carbon within 5 days, respectively. Comparatively, the degradation of pyrene increased to 60.63%, but the degradation of n-hexadecane decreased to 87.55% when these compounds were mixed. Additionally, identification and analysis of degradation metabolites of Rhodococcus sp. T1 in the above experiments showed that there were significant changes in alanine, methylamine, citric acid and heptadecanoic acid between sole and dual substrate degradation. The optimal conditions for degradation were then determined based on analysis of the pH, salinity, additional nutrient sources and liquid surface activity.Under the optimal conditions of pH 7.0, 35 °C, 0.5% NaCl, 5 mg·L^(-1) of yeast extract and 90 mg·L^(-1) of surfactant,the degradation increased in single or dual carbon sources. To our knowledge, this is the first study to discuss metabolite changes in Rhodococcus sp. T1 using sole substrate and dual substrate to enhance the long-chain alkanes and PAHs degradation potential.

Isolation of Secondary Metabolites with Antimicrobial Activities from Bacillus amyloliquefaciens LWYZ003

The strain LWYZ003, which can restrain multiple pathogens, was screened from the sediment of the ocean and identified as Bacillus amyloliquefaciens. Large-scale fermentation and modern chromatographic separation technologies(macroporous resin column chromatography, silica gel column chromatography, thin-layer chromatography and high-performance liquid chromatography) were used to separate antimicrobial products from the fermentation broth of marine-derived Bacillus amyloliquefaciens LWYZ003. Bioactive-guided separation was used in the term of seeking antimicrobial products from the secondary metabolites of Bacillus amyloliquefaciens LWYZ003. As a result, two natural products cycloheximide( 1) and trehalose( 2) were obtained. Their structures were elucidated by Fourier transform infrared spectroscopy, high-resolution mass spectrometry, ~1 H and ^(13) C nuclear magnetic resonance analysis. In the cylinder plate method, compound 1 exhibited stronger antimicrobial activities than compound 2 against Micrococcus luteus, and also exhibited wider antimicrobial spectrum than compound 2. In conclusion, isolation of bioactive secondary metabolites from marine Bacillus sp. has enormous potentials in finding suitable antibiotics to inhibit multiple pathogens.

Combination of a crude oil-degrading bacterial consortium under the guidance of strain tolerance and a pilot-scale degradation test

Under the guidance of strain tolerance, a new combination method for crude oil-degrading bacterial consortium was studied. Firstly, more than 50 efficient crude oil-degrading and biosurfactant producing bacteria were isolated from petroleum-contaminated soil and water in Tianjin Binhai New Area Oil field, China. Twenty-four of them were selected for further study. These strains were identified as belonging Pseudornonas aeruginosa, Bacillus subtilis, Brevibacillus brevis, Achrornobacter sp., Acinetobacter venetianus, Lysinibacillus rnacroides, Klebsiella oxytoca, Stenotrophornonas rhizophila, Rhodococcus sp. and Bacillus thuringiensis. A shake-flask degradation test revealed that 12 of these strains could degrade over 50% of 1% crude oil concentration in 7 d. Of these, 8 strains were able to produce biosurfactants. Furthermore, environmental tolerance experiments indicated that the majority of the strains had the ability to adapt to extreme environments including high temperatures, alkaline en- vironments and high salinity environments. A mixed bacterial agent comprising the strains WB2, W2, W3 and HA was developed based on the environmental tolerance tests and subjected to the pilot-scale degradation test indicating that this bacterial agent could degrade 85.2% of 0.8% crude oil concentration in 60 d. Our results suggest that the application of this mixed agent could remediate crude oil polluted soils in saline and alkaline environments.

Computational fluid dynamics simulation of a novel bioreactor forsophorolipid production

This paper describes three-dimensional computational fluid dynamics(CFD) simulations of gas–liquid flow in a novel laboratory-scale bioreactor contained dual ventilation-pipe and double sieve-plate bioreactor(DVDSB)used for sophorolipid(SL) production. To evaluate the role of hydrodynamics in reactor design, the comparisons between conventional fed-batch fermenter and DVDSB on the hydrodynamic behavior are predicted by the CFD methods. Important hydrodynamic parameters of the gas–liquid two-phase system such as the liquid phase velocity field, turbulent kinetic energy and volume-averaged overall and time-averaged local gas holdups were simulated and analyzed in detail. The numerical results were also validated by experimental measurements of overall gas holdups. The yield of sophorolipids was significantly improved to 484 g·L^(-1)with a 320 h fermentation period in the new reactor.

Increased sedimentation of a Pseudomonas–Saccharomyces microbial consortium producing medium chain length polyhydroxyalkanoates

Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs)production,which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia.Here,a medium chain length PHAs(mcl-PHAs)producing Pseudomonas-Saccharomyces consortium with xylose as the main substrate was studied.Mcl-PHAs accumulation increased from 12.69 mg·L^-1 to 152.3 mg·L^-1 without any optimization method.The presence of Saccharomyces cerevisiae,though in a relatively low concentration,improved the sedimentation of cell mass of the mixed culture by 60%.Reasons for better sedimentation of the consortium were complex:first,the length of Pseudomonas putida increased two to three times in the consortium;second,the positive surface charge of P.putida was neutralized by S.cerevisiae;third,the adhesion proteins on the surface of S.cerevisiae interacted with the P.putida.

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient(0-0.4043 g/g)in surface(5-10 cm)and subsurface(35-40 cm)petroleum-contaminated soil samples from the Dagang Oilfield,China.Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods,the bacterial diversity of the soil was studied.Subsequently,the environmental parameters were measured to analyze its relationship with the community variation.Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils,but no differences were observed in different depths of petroleum-contaminated soil.Meanwhile,many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties.Total petroleum hydrocarbon,total organic carbon,and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils.Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Optimal design of heat exchanger header for coal gasification in supercritical water through CFD simulations

Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.

Improvement of a highly sensitive and specific whole-cell biosensor by adding a positive feedback amplifier

In this study,we designed a Cd^(2+)whole-cell biosensor with both positive and negative feedback cascade am-plifiers in Pseudomonas putida KT2440(LTCM)based on our previous design with only a negative feedback amplifier(TCM).The results showed that the newly developed biosensor LTCM was greatly improved compared to TCM.Firstly,the linear response range of LTCM was expanded while the maximum linear response range was raised from 0.05 to 0.1μM.Meanwhile,adding a positive feedback amplifier further increased the fluorescence output signal of LTCM 1.11–2.64 times under the same culture conditions.Moreover,the response time of LTCM for detection of practical samples was reduced from 6 to 4 h.At the same time,LTCM still retained very high sensitivity and specificity,while its lowest detection limit was 0.1 nM Cd^(2+)and the specificity was 23.29(compared to 0.1 nM and 17.55 in TCM,respectively).In summary,the positive and negative feedback cascade amplifiers effectively improved the performance of the biosensor LTCM,resulting in a greater linear response range,higher output signal intensity,and shorter response time than TCM while retaining comparable sensitivity and specificity,indicating better potential for practical applications.

Screening and pilot-scale evaluation of a highly efficient pesticide-degrading Pseudomonas sp.strain BL5

The widespread use of pesticides has caused serious harm to ecosystems,necessitating effective and environmentally friendly treatment methods.Bioremediation stands out as a promising approach for pollutant treatment,wherein the metabolic activities of microorganisms can transform toxic pesticides into compounds with lower or no toxicity.In this study,we obtained eight pesticide-degrading strains from pesticide-contaminated sites through continuous enrichment and screening.Four highly efficient pesticide-degrading strains(degradation ratios exceeding 80%)were identified.Among them,Pseudomonas sp.BL5 exhibited the strongest growth(exceeding 10^(9) CFU·ml^(-1))and outstanding degradation of benzene derivatives and chlorinated hydrocarbons at both laboratory and pilot scales,with degradation ratios exceeding 98%and 99.6%,respectively.This research provides new tools and insights for the bioremediation of pesticide-related pollutants.

Design, analysis and application of synthetic microbial consortia

The rapid development of synthetic biology has conferred almost perfect modification on single cells,and provided methodological support for synthesizing microbial consortia,which have a much wider application potential than synthetic single cells.Co-cultivating multiple cell populations with rational strategies based on interacting relationships within natural microbial consortia provides theoretical as well as experimental support for the successful obtaining of synthetic microbial consortia,promoting it into extensive research on both industrial applications in plenty of areas and also better understanding of natural microbial consortia.According to their composition complexity,synthetic microbial consortia are summarized in three aspects in this reviewand are discussed in principles of design and construction,insights and methods for analysis,and applications in energy,healthcare,etc.

Surface display of carbonic anhydrase on Escherichia coli for CO_(2) capture and mineralization

Mineralization catalyzed by carbonic anhydrase(CA)is one of the most promising technologies for capturing CO_(2).In this work,Escherichia coli BL21(DE3)was used as the host,and the N-terminus of ice nucleation protein(INPN)was used as the carrier protein.Different fusion patterns and vectors were used to construct CA surface display systems forα-carbonic anhydrase(HPCA)from Helicobacter pylori 26695 andα-carbonic anhydrase(SazCA)from Sulfurihydrogenibium azorense.The surface display system in which HPCA was fused with INPN via a flexible linker and intermediate repeat sequences showed higher whole-cell enzyme activity,while the enzyme activity of the SazCA expression system was significantly higher than that of the HPCA expression system.The pET22b vector with the signal peptide PelB was more suitable for the cell surface display of SazCA.Cell frac-tionation and western-blot analysis indicated that SazCA and INPN were successfully anchored on the cell’s outer membrane as a fusion protein.The enzyme activity of the surface display strain E-22b-I RL S(11.43 U⋅mL^(−1) OD 600−1)was significantly higher than that of the intracellular expression strain E-22b-S(8.355 U⋅mL^(−1) OD 600−1)under optimized induction conditions.Compared with free SazCA,E-22b-I RL S had higher thermal and pH stability.The long-term stability of SazCA was also significantly improved by surface display.When the engineered strain and free enzyme were used for CO_(2) mineralization,the amount of CaCO_(3) deposition catalyzed by the strain E-22b-I RL S on the surface(241 mg)was similar to that of the free SazCA and was significantly higher than the intracellular expression strain E-22b-S(173 mg).These results demonstrate that the SazCA surface display strain can serve as a whole-cell biocatalyst for CO_(2) capture and mineralization.