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关键词： Turbulence fluctuation velocity   Oscillating-grid turbulence   Biofilm   Physical and chemical properties  

摘要： The flow velocity plays an important role in the growth and characteristics of biofilm in the bioreactor as well as its treatment efficiency, which has been a hot research topic. In a sewage treatment bioreactor, the type of flow is usually turbulence. According to the methods of Reynolds decomposition, the flow velocity of turbulence consists of the time-mean velocity and fluctuation velocity, which usually exist simultaneously in real flow. However, the current research on the influence of turbulence flow velocity mainly focuses on the time-mean velocity, while the fluctuation velocity has not been reported because of very difficult to control. To this end, in this paper, a laboratory oscillating-grid turbulence (OGT) bioreactor with zero time-mean velocity and only fluctuation velocity was designed. In this bioreactor, the fluctuation velocity could be easily manipulated by varying the operational parameters of the grid. Based on the numerical simulation of Gas-liquid two-phase flow, the distributions of fluctuation velocity and corresponding turbulence fluctuation intensity, gas holdup, and Reynolds stress were obtained. After that, the effects of the turbulent fluctuation intensity on the biofilm thickness, density, and composition of extracellular polymeric substances (EPS) were studied experimentally. The results showed that turbulent fluctuation had a significant effect on the physical and chemical properties of biofilms, and the fluctuation velocity promoted the increase in the biofilm density and the content of protein and carbohydrates in EPS. This study was intended to provide theoretical support for the design and operation optimization of bioreactors.

关键词： Real municipal wastewater   Operation temperature   Microbial community   Anaerobic membrane bioreactor   Biogas energy  

摘要： A submerged anaerobic membrane bioreactor (SAnMBR) was used in the treatment of real municipal wastewater at operation temperatures ranging from 15 degrees C to 25 degrees C and hydraulic retention time (HRT) of 6 h. The treatment process was evaluated in terms of organic removal efficiency, biogas production, sludge growth and membrane filtration. During long-term operation, the SAnMBR achieved chemical oxygen demand removal efficiencies of about 90% with a low sludge yield (0.12-0.19 g-VSS/g-CODrem) at 20-25 degrees C. Approximately 1.82-2.27 kWh/d of electric energy was generated during the wastewater treatment process at 20-25 degrees C, 0.67 kWh/d was generated at 15 degrees C. The microbial community analysis results showed that microbial community was dominated by aceticlastic methanogens, coupled by hydrogenotrophic methanogens and a very small quantity of methylotrophic methanogens. It was also shown that the stabilization of the microbial community could be attributed to the carbohydrate-protein degrading bacteria and the carbohydrate degrading bacteria.

关键词： Exopolysaccharide   High-throughput Sequencing   Low C   N Ratio   Nitrate Removal   Suspended Membrane Bioreactor  

摘要： A suspended membrane bioreactor (SMBR) was employed to treat low carbon to nitrogen (C/N) ratio wastewater. The suspended membranes amplified by Comamonas sp. YSF15 were collected to develop the SMBR, which showed excellent performance for nitrate (NO3) removal. The maximum nitrate removal efficiency of 95.22% was obtained at an initial nitrate concentration of 20 mg L-1, HRT of 6 h, and C/N=2.5: 1 (molar ratio). In addition, the polysaccharide (PS) and protein (PN) compositions of the soluble microbial products (SMP), extracellular polymeric substances (EPS) and the Fourier transform infrared (FTIR) spectra indicated that the suspended membrane utilized its SMP and EPS as reserve C source to achieve higher denitrification performance under the low C/N ratio. With the increase of pH, the generated SMP and EPS in SMBR continued to increase. The increase in PS content was significantly greater than that of PN, thus forming a suspended membrane with a certain mechanical strength. High-throughput sequencing data indicated that Comamonas sp. YSF15 played a key role in effective nitrate removal by SMBR. It can adapt to a nutrient-deficient environment, especially low (C/N) ratio, and greatly increase in the late operation of the reactor.

关键词： Heat transfer coefficient   Mass transfer coefficient   Membrane distillation bioreactor   Submerged direct contact membrane distillation  

摘要： The mass and heat transfer mechanisms of the membrane distillation bioreactor (MDBR) system used for hospital wastewater treatment were determined. The initial flux and balance flux of the system were determined. The total mass transfer resistance calculated for the system increased by 72 % when the system reached equilibrium. Considering the temperature polarization coefficient, it is clear that the system was controlled by mass resistance.

关键词： cascade reaction   chemodynamic therapy   dendritic cells   immune system activation   immunogenic cell death  

摘要： Traditional chemo-immunotherapy can elicit T cell immune response by inducing immunogenic cell death (ICD), however, insufficient ICD limits the lasting antitumor immunotherapeutic efficacy. Herein, tadpole-ovoid manganese-doped hollow mesoporous silica coated gold nanoparticles (Au@HMnMSNs) as biodegradable catalytic cascade nanoreactors are constructed to generate intratumoral high-toxic hydroxyl radicals combined with DOX and Aspirin (ASA) for enhancing the induction of ICD and maturation of dendritic cells (DCs). The released Mn2+ can catalyze endogenous H2O2 to hydroxyl radicals, while internal gold nanoparticles mimetic glucose oxidase (GOx) converted glucose into H2O2 to accelerate the generation of hydroxyl radicals. On the other hand, tadpole oval-structured Au@HMnMSNs can avoid the inactivation of gold nanoparticles due to strong protein adsorption. The introduction of ASA is to recruit DCs and cytotoxic T lymphocytes (CTLs) to tumor sites and restrain the intratumoral infiltration of immunosuppressive cells by decreasing the expression of prostaglandin E2 (PGE(2)). Accordingly, this work presents a novel insight to introduce GOx-like catalytic cascade ICD nano-inducer into antitumor immunotherapy for synergistic tumor therapy.

关键词： FA   Partial nitrification   Microbial community   Metabolic pathway   Functional gene  

摘要： During nitrification, the varieties of microbial structures, metabolic pathways and functional profiles in four parallel laboratory-scale sequencing batch reactors (SBRs) with 0.5, 5, 10 and 15 mg/L of free ammonia (FA) concentrations were analyzed by high-throughput sequencing of the 16S rRNA gene. The SBRs were named S-0.5, S-5, S-10 and S-15, respectively. Ammonia removal via the nitrate pathway was achieved in S-0.5 and S-5 throughout the whole experimental period, while ammonia removal via the nitrite pathway was established in S-10 and S-15 after 89 and 146 day, respectively. The key finding of this study is that both the microbial diversity and richness were significantly affected (p < 0.05) by the FA concentration at different taxonomic levels. The most dominant taxa of S-5, S-10 and S-15 were same, and mainly included Thauera while S-0.5 was mainly composed of Zoogloea. Linear discriminant analysis (LDA) effect size (LEfSe) analysis was used to identify unique biomarkers in SBR activated sludge (AS) sample. The functional genera and enzyme in the four SBRs are similar but different in abundance and they are responsible for the removal of organics and nitrogen. Moreover, metabolic pathways are similar by PICRUSt analysis. The relative proportions of pathway-specific genes involved in some metabolic pathways differed to some extent. The ammonia oxidation rate was positively linked to Nitrosomonas and amo (both Spearman correlation coefficients (rho) = 0.777) while the nitrite oxidation rate was positively linked to Nitrospira (rho = 0.777) by co-occurrence network analysis. This work deciphered the response of microbial characteristics to different FA constraints in AS process and could provide helpful information for revealing the biological mechanism of FA inhibition on nitrogen removal.

关键词： β   ‐   catenin nuclear translocation   adherens junction dynamics   bioreactor   fluid shear stress   mechanopluripotency   mouse embryonic stem cells   vinculin  

摘要： The expansion of pluripotent stem cells (PSCs) as aggregates in stirred suspension bioreactors is garnering attention as an alternative to adherent culture. However, the hydrodynamic environment in the bioreactor can modulate PSC behavior, pluripotency and differentiation potential in ways that need to be well understood. In this study, we investigated how murine embryonic stem cells (mESCs) sense fluid shear stress and modulate a noncanonical Wnt signaling response to promote pluripotency. mESCs showed higher expression of pluripotency marker genes, Oct4, Sox2, and Nanog in the absence of leukemia inhibitory factor (LIF) in stirred suspension bioreactors compared to adherent culture, a phenomenon we have termed mechanopluripotency. In bioreactor culture, fluid shear promoted the nuclear translocation of the less well-known pluripotency regulator beta-catenin and concomitant increase of c-Myc expression, an upstream regulator of Oct4, Sox2, and Nanog. We also observed similar beta-catenin nuclear translocation in LIF-free mESCs cultured on E-cadherin substrate under defined fluid shear stress conditions in flow chamber plates. mESCs showed lower shear-induced expression of pluripotency marker genes when beta-catenin was inhibited, suggesting that beta-catenin signaling is crucial to mESC mechanopluripotency. Key to this process is vinculin, which is known to rearrange and associate more strongly with adherens junctions in response to fluid shear. When the vinculin gene is disrupted, we observe that nuclear beta-catenin translocation and mechanopluripotency are abrogated. Our results indicate that mechanotransduction through the adherens junction complex is important for mESC pluripotency maintenance.

关键词： Anaerobic Baffled Biofilm Membrane   Bioreactors   Liquor condensate wastewater   Reactor configurations   Fouling mitigation   Methanogenic toxicity  

摘要： A novel anaerobic baffled biofilm-membrane bioreactor (AnBB-MBR) was developed to treat industrial liquor condensate. In order to minimize membrane fouling, three different reactor configurations of R1:No media (anaerobic baffled MBR), R2:FF (Fixed Film AnBB-MBR) and R3:FF + MVB (Fixed Film and Moving Bed AnBBMBR) were evaluated at the same operating hydraulic retention time of 3 days. The specific fouling rates of the ceramic membranes were 0.98, 0.84 and 0.5 kPa/L/m2 for R1:No media, R2:FF and R3:FF + MVB, respectively. The R2:FF and R3:FF + MVB reactors could mitigate the membrane fouling rates by 14.1% and 48.9%, compared to R1:No media due to biomass retention in the fixed film and mechanical scouring of the MVB. From the microbial community analysis, higher relative abundances of Methanosaeta were found in the biofilm whereas more Methanobacterium was found in the suspended sludge. Moreover, higher accumulations of humic and fulvic substances in the system could inhibit the methanogenic activity.

关键词： Biofilm   Biotransformation   Sulfamethoxazole   Erythromycin   Ampicillin  

摘要： Although extensive research to date has focused on enhancing removal rates of antibiotics from municipal wastewaters, the transformation products formed by anaerobic treatment processes remain understudied. The present work aims to examine the possible roles that the different microbial communities of an anaerobic membrane bioreactor (AnMBR) play in the transformation of antibiotics during wastewater treatment. As part of this work, sulfamethoxazole, erythromycin, and ampicillin were added in separate stages to the influent of the AnMBR at incremental concentrations of 10, 50, and 250 mu g/L each. Antibiotic-specific transformation products detected during each stage, as identified by high resolution LC-MS, are reported herein. Results suggest that both isoxazole (sulfamethoxazole) and beta-lactam (ampicillin) ring opening could be facilitated by the AnMBR's bioprocess. Microbial community analysis results indicated that relative activity of the system's suspended biomass consistently shifted towards syntrophic groups throughout the duration of the experiment. Notable differences were also observed between the suspended biomass and the AnMBR's membrane biofilms. Membrane-attached biofilm communities showed high relative activities of several specific methanogenic (Methanothrix and Methanomethylovorans), syntrophic (Syntrophaceae), and sulfate-reducing (Desulfomonile) groups. Such groups have been previously identified as involved in the formation of the antibiotic degradation products observed in the effluent of the AnMBR. The activity of these communities within the biofilms likely confers certain advantages that aid in the biotransformation of the antibiotics tested.

关键词： Salinispora tropica   Flask and bioreactor cultivation   Nitrogen sources   Biomass growth kinetics  

摘要： Objective Marine actinomycetes from the genus Salinispora have an unexploited biotechnological potential. To accurately estimate their application potential however, data on their cultivation, including biomass growth kinetics, are needed but only incomplete information is currently available. Results This work provides some insight into the effect of temperature, salinity, nitrogen source, glucose concentration and oxygen supply on growth rate, biomass productivity and yield of Salinispora tropica CBN-440(T). The experiments were carried out in unbaffled shake flasks and agitated laboratory-scale bioreactors. The results show that the optimum growth temperature lies within the range 28-30 degrees C, salinity is close to sea water and the initial glucose concentration is around 10 g/L. Among tested nitrogen sources, yeast extract and soy peptone proved to be the most suitable. The change from unbaffled to baffled flasks increased the volumetric oxygen transfer coefficient (k(L)a) as did the use of agitated bioreactors. The highest specific growth rate (0.0986 h(-1)) and biomass productivity (1.11 g/L/day) were obtained at k(L)a = 28.3 h(-1). A further increase in k(L)a was achieved by increasing stirrer speed, but this led to a deterioration in kinetic parameters. Conclusions Improvement of S. tropica biomass growth kinetics of was achieved mainly by identifying the most suitable nitrogen sources and optimizing k(L)a in baffled flasks and agitated bioreactors.