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关键词： Bacterial quorum quenching   Biofouling control   Biostimulation   Layered media structure   Membrane bioreactor  

摘要： Efficient media designs for microbial quorum quenching (QQ) are essential to enable maximal biofouling control in membrane bioreactors (MBRs). Here we introduce a novel, double-layered, biocarrier design, which has QQ bacteria in the shell layer with biostimulating agents in the core, for effective membrane biofouling control. Confining the biostimulant within dense polymer materials permits its controlled release over an extended period. The provision of the biostimulant from the core to the outer shell, where the QQ bacteria are encapsulated, facilitates their prolonged survival and active life. The core-shell structured QQ bead with the stimulant inside, which inhibits biofilm formation, shows the best fouling mitigation in laboratory testing of MBRs, while enhancing signal molecule degradation and lowering exopolymer secretion. This new, layered QQ bead, which has dual functions of bioaugmentation and biostimulation, supports a highly efficient and sustainable anti-biofouling strategy. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： hydrolysis acidification   MBR   membrane fouling   decolorization   microbial diversity   seed sludge  

摘要： Cost-effective treatment of dyeing wastewater remains a challenge. In this study, a newly designed hydrolysis acidification flat-sheet ceramic membrane bioreactor (HA-CMBR) was used in treating high-strength dyeing wastewater. The start-up phase of the HA-CMBR was accomplished in 29 days by using cultivated seed sludge. Chemical oxygen demand (COD) removal rate reached about 62% with influent COD of 7800 mg/L and an organic loading rate of 7.80 kg-COD/(m(3)d). Chromaticity removal exceeded 99%. The results show that the HA-CMBR has good removal performance in treating dyeing wastewater. The HA-CMBR could run with low energy consumption at trans-membrane pressure (TMP) <10 kPa due to the good water permeability of the flat-sheet ceramic membrane. New strains with 92%-96% similarity to Alkalibaculum bacchi, Pseudomonas sp., Desulfovibrio sp., and Halothiobacillaceae were identified in the HA-CMBR. Microbial population analysis indicated that Desulfovibrio sp., Deltaproteobacteria, Halothiobacillaceae, Alkalibaculum sp., Pseudomonas sp., Desulfomicrobium sp., and Chlorobaculum sp. dominated in the HA-CMBR.

关键词： Soluble microbial products   Proteins   Humic-like substances   Membrane fouling   Operating conditions  

摘要： Soluble microbial products are one of the major fouling agents in membrane bioreactor (MBR). It is accepted that high molecular weights polysaccharides are the main contributors to membrane fouling but the presence in bulk solution of proteins and humic-like substances make fouling layer more complex. To better understand the role of both components in fouling establishment, they were quantified and characterized in bioreactor and permeate under various operating conditions (sludge retention time (SRT), synthetic or real wastewater (SWW or RWW), rapid variation of food to microorganisms (F/M) ratio). With SWW at hydraulic retention time (HRT) of 24 h, a larger part of proteins possessing small molecular weights (< 1 kDa) were obtained with increasing SRT from 20 to 50 d. At 50 d, these proteins present better retention (93%) and could participate in lowering gel layer porosity. MBR operating at SRT of 20 d was then preferable. At respective SRT and HRT of 50 d and 24 h with SWW, F/M ratio decrease (from 0.2 to 0.1 kg (COD).kg(MLVSS)(-1).d(-1) during 24 h) provoked implementation of a compact fouling layer which provoked a high TMP increase (0.83 kPa.h(-1)). Biodegradation of proteins involved in bio clusters structures were implied in this phenomenon.

关键词： Antibiotics   Anoxic   Biodegradation   Membrane bioreactor   Solid waste leachate  

摘要： This study aims to investigate the influence of high antibiotics doses on the efficiency of an anoxic-aerobic membrane bioreactor (ANX-AMBR) in treating solid waste leachate for one-year operation without sludge withdrawal. Two doses of a mixture of norfloxacin (NOR), trimethoprim (TRM), sulfamethoxazole (SMX) and tetracycline (TC), a total of 4 mg L-1 (1 mg L-1 each) and a total of 20 mg L-1 (5 mg L-1 each), had been fed into the ANX-AMBR operated at HRTs of 12 h and 24 h. A high efficiency of organic matter removal could be achieved > 90% in all conditions. The highest elimination of NOR, 77%;TRM/SMX/TC, 50-57%, was found under a 12 h-HRT with the antibiotic dose of 4 mg L-1. However, high antibiotic doses gave adverse effects on nitrite reduction-oxidation including antibiotic removal efficiency in the ANX-AMBR. Additionally, the extra cellular polymeric substances were produced remarkably in the system after the antibiotic dose of 20 mg L-1. Mass balance analysis suggests that biodegradation was a major role in antibiotics removal in this system. Batch studies showed that the first order kinetics rate constants (k) of antibiotics biodegradation were 0.509-1.573 d(-1) of ANX and 0.128-0.516 d(-1) of AMBR.

关键词： Tissue engineering   Bioreactor   Alginate   Explant   Isolation   Mesenchymal stem cell   Umbilical cord  

摘要： One of most important issue in the field of regenerative medicine is selection of appropriate cells, scaffolds and bioreactors. The present study aimed to investigate the appropriate method for the isolation of human UC-MSCs cells from explant cultured in alginate scaffold within novel perfusion bioreactor. MSCs were isolated with explant method and CD markers such CD73, CD31, CD90 and CD105 as were analyzed by flow cytometry. The culture chamber of the novel perfusion bioreactor was made from Plexiglas and housed the cell/scaffold constructs in the central part and the medium for the whole culture period. The flow behavior within the bioreactor chamber were performed for closed and open bypass systems. The shear stress profiles simulated using CFD modeling. The fluid flow distribution within the bioreactor chamber was performed in PBS solution containing a blue colorant. UC explants were resuspended in sodium alginate and were allowed to polymerize and placed in the perfusion bioreactor and cultured. MSCs were positive for mesenchymal markers such as CD73 and CD31. All 3D Perfusion bioreactor parts, except peristaltic pump was sterilizable by autoclaving. Results of CFD indicated very low wall shear stress on surface of culture chamber at flow rate 2 ml/min. The maximum wall shear stress was 1.10 x 10(-3) m/s = 0.0110 dyne/cm(2) (1 Pa = 10 dyne/cm(2)). The fluid flow distribution within the alginate gel initially exhibited oscillation. In comparison, when encapsulated explants were placed in the perfusion bioreactor, cell proliferation appeared faster (4.6 x 10(11) +/- 9.2 x 10(11)) than explants cultures in 2D conventional culture method (3.2 x 10(11) +/- 1 x 10(11)). Proliferated cell formed several colonies. Migration of chondrocytes to the periphery of the alginate bead was visible after 1 week of culture. Perfusion bioreactor with low shear stress and alginate hydrogel improve cell isolation and expansion and eliminate cell passaging and enhance colony forming

关键词： Airlift bioreactor   ALR   Bodenstein number   Helical flow promoter   Mixing   Mixing time  

摘要： Cultivation of aerobic microorganisms typically requires rapid, but gentle and simultaneously energy efficient mixing in bioreactors to prevent high gradients between local concentrations. The mixing efficiency in a pilot scale airlift bioreactor with helical flow promoters was investigated with varying air inputs. Helical flow promoters were helical tubes attached to riser or downcomer, or both and besides acting as flow promoter they were used as additional gas spargers. Mixing time, circulation time, dimensionless mixing time and Bodenstein number were used as assessment parameters to analyze the mixing efficiency of different airlift setups with helical flow promoters. Introducing air through the helical flow promoter in the downcomer zone prolonged the circulation time, but shortened the mixing time and decreased the Bodenstein number. Low Bodenstein number indicated an improved axial dispersion. Mixing was more related to dispersion in the airlift reactor with helical flow promoter in the downcomer zone whereas in a regular airlift reactor mixing was related to liquid circulation speed.

关键词： Peristaltic roller pump   Pulse damper   Dampener   Pulsatile flow   Endothelial cells   Bioreactor   Shear stress   MAP kinase   Cinema PIV  

摘要： PurposePeristaltic pumps (PP) are favored in flow bioreactors for their non-contact sterile design. But they produce pulsatile flow, which is consequential for the cultured cells. A novel pulse damper (PD) is reported for pulsatility *** designwas implemented to target static pressure pulsatility and flow rate (velocity) pulsatility from a PP. Damping effectiveness was tested in a macro-scale, closed-loop recirculating bioreactor mimicking the aortic arch at flow rates up to (4L/min). Time-resolved particle image velocimetry was used to characterize the velocity field. Endothelial cells (EC) were grown in the bioreactor, and subjected to continuous flow for 15min with or without *** PD was found to be nearly 90% effective at reducing pulsatility. The EC exposed to low PP flow without PD exhibited distress signaling in the form of increased ERK1/2 phosphorylation (2.5 folds) when compared to those exposed to the same flow with PD. At high pump flow without PD, the cells detached and did not survive, while they were perfectly healthy with *** pulsatility from PP causes EC distress at low flow and cell detachment at high flow. Elevated temporal shear stress gradient combined with elevated shear stress magnitude at high flow are believed to be the cause of cell detachment and death. The proposed PD design was effective at minimizing the hemodynamic stressors in the pump's output, demonstrably reducing cell distress. Adoption of the proposed PD design in flow bioreactors should improve experimental protocols.

关键词： Biofilm reactor   Biomineralization   Community diversity   Denitrification   Pseudomonas sp.  

摘要： The effects of combined different strains on a simultaneous denitrification and biomineralization process were examined. The influence of sodium succinate concentration, pH, and hydraulic retention time on nitrate and hardness removal was evaluated in bioreactors. Experimental results indicated that high nitrate and hardness removal efficiencies were obtained under optimum conditions. The community diversity was markedly influenced by the concentration of sodium succinate. The findings proved that Pseudomonas sp. H117 and Pseudomonas sp. H2 played a key role in the process of nitrate and hardness removal. The main component of sedimentation generated from the bioreactor was detected as calcium ion precipitation by scanning electron microscopy and X-ray diffraction.

关键词： Membrane fouling   Membrane bioreactor   Gel layer   Hydrogen bonding   Filtration resistance  

摘要： Gel layer formation in some cases directly determines membrane fouling extent in membrane bioreactors (MBRs). While hydrogen bonding interactions extensively exist in gelling foulants and sludge suspension, their exact roles in fouling remain unveiled. Filtration results in this study showed that, specific filtration resistance (SFR) of a gel layer formed in the MBR was as high as 2.06x10(19)m(-1).kg(-1) at 20 degrees C, and moreover, SFR of both the real gel and model gel (Poly(N-isopropylacrylamide) (PNIPAM)) decreased with temperature. Fouriertransform infrared spectroscopy (FTIR) analysis indicated that gel samples were abundant of good hydrogen bonding donors/acceptors to form hydrogen bonding, and hydrogen bonding strength decreased with temperature. From viewpoint of free energy, mathematical models depicting roles of hydrogen bonding were proposed. For the first time, contribution level of hydrogen bonding effects to total gel SFR was quantified to be around 20%. These results offered in-depth insights into membrane fouling in MBRs.

关键词： Continuous formaldehyde biodegradation   Substrate inhibition kinetics   Polyurethane support   CFD simulation   Eulerian computations  

摘要： This study focuses on continuous formaldehyde (FA) biodegradation by Ralstonia eutropha immobilized on polyurethane foam in a semi-pilot-scale plug flow packed-bed bioreactor. The stepwise increasing of the influent FA concentration from 43.9 to 1325.1mgL(-1) was studied in the bioreactor during 70days of operation. A complete removal of FA was achieved for inlet concentration up to 425.5mgL(-1) and the initial specific biodegradation rate reached to its maximum value about 44.3mgg(cell)(-1)h(-1) at 425.5mgL(-1). However, further increase of inlet concentration resulted in decrease of the biodegradation performance of the immobilized cells due to the inhibitory effect of FA on the enzymatic system involved in the biodegradation process. Based on kinetic modeling results, the Luong equation with the following constants could best describe the behavior of the bio-system: maximum specific FA biodegradation rate (q(max)) of 124mgg(cell)(-1)h(-1), half-saturation constant (K-S) of 337.2mgL(-1), maximum degradable FA concentration (S-max) of 1582mgL(-1), and shape factor (n) of 1.49. Also, three-dimensional simulation of the bioreactor was performed using an integrated computational fluid dynamics (CFD) approach that takes into account both the biokinetic constants of the immobilized system as well as the fluid properties under steady-state condition. Eulerian computations successfully anticipated the concentration gradients through the reactor for different inlet FA concentrations, and uniform vertical velocity pathlines and non-dispersed plug flow inside the reactor were verified by the presented velocity distribution and flow streamlines.