课程文献中心 更多>>

关键词： Dinoflagellate   Symbiodinium   Porous substrate bioreactor   Peridinin   Immobilised cultivation  

摘要： Dinoflagellates are a natural source for unique secondary metabolites and pigments, which have considerable potential for applications in biomedical drug development and cosmetics. However, the technical cultivation of dinoflagellates in commonly used suspension-based closed photobioreactors (PBRs) has been shown to be difficult due to the sensitivity of the cultures to turbulence and shear forces. To overcome these and other constraints of suspension cultivation, immobilised cultivation of the dinoflagellate Symbiodinium voratum has been performed using a twin-layer porous substrate bioreactor (TL-PSBR). By optimising biomass growth using printing paper as substrate, a maximal biomass growth rate of 7.8g dry weight m(-2) growth area day(-1) was measured over a period of 40days at the relatively high-light intensity of 600mol photons m(-2)s(-1) and 2% (v/v) CO2. Linear growth of the S. voratum biofilm was observed over 40days, and a maximal biomass standing crop of 305gm(-2) was gained. Synthesis of the potentially high-value carotenoid pigment peridinin, however, was favoured at low-light conditions (100mol photons m(-2)s(-1)). By combining maximal biomass growth at high-light conditions with maximal peridinin accumulation at low-light conditions in a two-phase approach (14days cultivation at 600mol photons m(-2)s(-1) and 2% CO2 followed by 14days at 100mol photons m(-2)s(-1) and ambient air), a peridinin productivity of 51.4mg peridinin m(-2)day(-1) was measured (about 30% higher than the values determined at either low- or high-light conditions). Using the two-phase approach, peridinin accumulated to a standing crop of similar to 1g peridinin m(-2) after 28days of cultivation in a bench-scale TL-PSBR with a peridinin content in the dry biomass of 1% (w/w). Symbiodinium voratum may thus be a suitable source of peridinin for a diverse range of applications when grown in a twin-layer porous substrate bioreactor.

关键词： Probiotic bacteria   Lactic acid bacteria   Fermentation process   Bacteriocin-like inhibitory substance   Natural antimicrobial  

摘要： Bacteriocins are peptides produced by various species of bacteria, especially lactic acid bacteria (LAB), which have a large spectrum of action against spoilage bacteria and foodborne pathogens. However, when not entirely characterized, they are alternatively called bacteriocin-like inhibitory substances (BLIS). Pediococcus pentosaceus ATCC 43200 grew and produced BLIS optimally when cultivated anaerobically in bioreactor for 24h at 30 degrees C and 200rpm in De Man, Rogosa and Sharp (MRS) medium supplemented with 1.5% peptone. Under such optimal conditions, the cell mass concentration (3.41g/L) was 66% higher, the generation time (1.28h) 38% shorter and the BLIS activity against different indicator strains significantly higher than in MRS medium without any supplement taken as a control, and the exponential phase started 4h before. The agar diffusion method showed BLIS inhibition halos against LAB strains with diameter in the range 11.0-19.5mm and specific areas between 377.1 and 2654.6mm(2)/mL, while BLIS activity against Listeria strains was better quantified by the liquid medium assay that showed, for the fermented broth without any dilution, 100 and 50% inhibition of Listeria innocua and Listeria seeligeri growth, respectively. These results highlight the potential of P. pentosaceus BLIS as a natural antimicrobial for application in the food industry.

关键词： (S)-4-fluorophenylglycine   Immobilized amidase   Kinetic resolution   Continuous production   Packed bed bioreactor  

摘要： To develop a highly efficient method for aprepitant chiral intermediate (S)-4-fluorophenylglycine, a continuous reaction system was established in packed bed bioreactor using amidase covalently immobilized on epoxy resin as biocatalyst. The epoxy resin was firstly modified by metal-chelate method and functional groups (Cu2+-IDA) generated were able to rapidly adsorb amidases, which were further covalently bound onto the modified resin with 90.1% immobilization yield and 80.2% activity recovery. The immobilized amidase exhibited excellent thermal stability with the longest half-life of 1456.8 h at 40 degrees C ever reported. (S)-4-fluorophenylglycine was continuously produced using the reaction system with 49.9% conversion, 99.9% ee, and an outstanding space-time yield of 5.29 kg L-1 d(-1). Moreover, the efficient reaction system exhibited a high operational stability and retained 86.3% catalytic activity after 25-day continuous operation. This efficient continuous bioprocess presents great industrial potential for large-scale production of (S)-4-fluorophenylglycine.

关键词： Silk textile wastewater   Electrochemical coagulation   Fe and Al electrodes   Membrane bioreactor   Filterability  

摘要： Raw real silk textile wastewater was treated using batch electrochemical coagulation (ECC) method. Iron and aluminum electrodes in monopolar parallel arrangement were using a specific electrode area to volume of 24 m(2)/m(3) and a cell voltage of 6 V as the optimal operating condition. Chemical oxygen demand removal ranged from 88% to 92% for iron and aluminum electrodes. Settleability and filterability characteristics of ECC-treated wastewater were at ease. UV-visible spectral analysis was carried out to evaluate the efficiency of ECC treatment for color removal from textile wastewater. An electrolysis time of 10-20 min was sufficient to remove maximum apparent color from the solution. The sludge obtained after electrochemical treatment (ECT) was analyzed for its composition by energy-dispersive spectroscopy. The supernatant from ECT after sludge settling was further treated using membrane bioreactor (MBR) for removal of trace pollutants/solids residues. The results proved the suitability of the dual hybrid treatment process for the complete removal of pollutants/contaminants combining ECC and MBR with similar to 75% clear water reclamation.

关键词： PVDF-SCNT   MBRs   High water flux   Anti-fouling   Non-toxic   Gram-negative bacteria  

摘要： The ultrafiltration (UF) membrane in membrane bioreactor (MBR) technology is the most suitable in a wastewater treatment plant (WWTP). In MBR systems, bacteria consume organic waste for energy to survive. Hence, the membranes should be non-toxic to the bacteria but still possess antifouling capability. In this study, carbon nanotube (CNT)- and sulphonated CNT (SCNT)-blended ultrafiltration polyvinylidene fluoride (PVDF) membranes were fabricated with the aim of conserving the bacterial population. The successful sulphonation of CNTs was observed by X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron microscopy. The porosity of PVDF-CNT and-SCNT membranes was 81 and 84%, respectively. The mean pore size was 50 and 60 nm, respectively, and the corresponding water flux experiment was 360.43 and 680 L m(-2) h(-1). The fouling recovery ratio (FRR) of the CNTs and SCNTs were 72.74 and 83.52%, respectively. In addition, the BSA (bovine serum albumin) rejection was 90% in the PVDF-SCNT. The CNTs and SCNTs (150 mu g/m L) had a significant antibacterial effect against Escherichia coli, Pantoea agglomerans, and Pseudomonas graminis isolated from full scale MBR with 60% cell viability. On the other hand, PVDF-CNT and-SCNT membranes were nontoxic (90%, p < 0.0001) to the bacterial population. Therefore, the fabricated UF membranes have sustainable antifouling properties and are non-toxic to bacteria. This study suggests that PVDF-CNT and-SCNT are promising materials for MBR systems in WWTPs. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： 2,3-butanediol   Enterobacter ludwigii   Fermentation optimisation   Volumetric oxygen transfer coefficient (k(L)a)   Techno-economic evaluation  

摘要： This study focuses on the optimisation of 2,3-butanediol (BDO) production in fed-batch cultures carried out with the bacterial strain Enterobacter ludwigii using very high polarity (VHP) sugar from sugarcane mills. Various k(L)a values were evaluated using either complex or synthetic fermentation media demonstrating that the latter enhance BDO production efficiency with low by-product formation. The pH (6.3) and temperature (33.9 degrees C) employed in fed-batch bioreactor cultures has been optimised via experimental design. Fed-batch cultures carried out at the optimum temperature and pH and varying k(L)a values resulted in BDO concentration, yield and productivity of 86.8 g/L, 0.37 g/g and 3.95 g L-1 h(-1). Using this fermentation efficiency, the minimum selling price of BDO for annual production capacities of 10,000 t and 50,000 t was estimated at $3.12/kg and $2.67/kg, respectively, for a VHP cane sugar market price of $0.4/kg.

关键词： Sludge retention time   Sludge property   SMP   Membrane fouling  

摘要： Long-term sludge filterability and membrane fouling were investigated in a membrane bioreactor (MBR) with different sludge retention times (SRTs). The effect of SRT was evaluated systematically in terms of biomass evolution and sludge filterability such as modified fouling index (MFI) and specific cake resistance (a). The membrane fouling rate induced by the activated sludge mixed liquor in each MBR was also analyzed based on transmembrane pressure profiles and resistance-in-series model. Food to microorganism ratio gradually decreased close to 0.30 kg COD/(kg VSS d) with increasing SRT. There were no significant differences of the sludge growth rate, organic degradation rate, and the sludge yield for the MBRs. Sludge filterability significantly improved, described by the decreased MFI and a of the mixed liquor in the MBR at longer SRTs (above 20 d). The reduction of the soluble microbial products (SMP) content was relatively small as compared with a decrease in a. Lower filtration resistances were measured at SRT of 40 d coincided with lower polysaccharides and protein concentration in SMP and higher ratio of protein/polysaccharides. MBR at appropriate SRT (40 d) with a stable and high-quality permeate as well as membrane fouling mitigation could be adopted in the full-scale application.

摘要： Background. Mitral valve (MV) regurgitation constitutes an increasing burden of adult and pediatric cardiac disease tending to worsen over time. Whether altered mechanical forces on leaflets cause valve disease is unknown. Here we show that MV leaflet coaptive strain disruption alters expression of genes critical to leaflet homeostasis. Methods. We used a flow-culture bioreactor of rat MVs with flow-induced cyclic coaptation (cycling valve group;n = 4) or in a sustained open state (open valve group;n = 4). After 3 days of culture, leaflet RNA expression was profiled. Results. More than 48 genes exhibited markedly changed expression when coaptive leaflet strain was disrupted for 3 days (change >fourfold;p < 0.05;cycling vs open valves). Genes exhibiting highly altered expression included Angpt2, Vegf, Cd74, RT1-Da (HLA-DRA), and Igfbp3. Pathway analysis indicated the most significant signaling pathways regulating the expression changes were Hif1 alpha and Tnf alpha when MV closure was disrupted. Conclusions. Disruption of normal MV coaptive strain markedly alters the expression of leaflet genes, demonstrating that cyclic strain is critically important to leaflet homeostasis. We demonstrate a pattern of MV gene expression changes in which hypoxia signaling is prominently increased in response to disrupted strain cycles. Coaptive strain regulation of MV leaflet homeostasis implicates altered strain as a mechanism potentially initiating valve disease. Early repair may prevent progression of disease driven by altered coaptation. (C) 2019 by The Society of Thoracic Surgeons

关键词： global warming   greenhouse gas   membrane bioreactors   Wastewater   wastewater treatment  

摘要： Wastewater treatment plants (WWTPs) using membrane bioreactor (MBR) technology have been considered a significant source of greenhouse gas (GHG) emissions. This study chose a small-scale wastewater treatment plant using MBR technology to estimate its potential for GHG emissions. The total GHG emissions from this wastewater treatment plant ranged from 2,802 to 11,946 kg CO2-eq/month within the 4-year study period, and they were mainly attributable to electricity consumption (79.94%) followed by chemical usages (17.13%) and on-site GHG emissions (2.93%). The on-site GHG emissions varied monthly, but most of them ranged from 80 to 160 kg CO2-eq/month. The aeration tank was an important operating unit for GHG emissions. Off-site GHG emissions mainly came from carbon dioxide (CO2) emissions resulting from electricity consumption. The results of this study provide useful information about the potential of GHG emissions from WWTPs using MBR technology and indicate that WWTPs can be sustainably managed. (C) 2018 Water Environment Federation

关键词： ATF   hollow fibers   perfusion cell cultures   product retention   TFF  

摘要： Tangential flow filtration (TFF) and alternating tangential flow (ATF) filtration technologies using hollow fiber membranes are commonly utilized in perfusion cell culture for the production of monoclonal antibodies;however, product retention remains a known and common problem with these systems. To address this issue, commercially available hollow fibers ranging from several hundred kilo-Daltons (kDa) to 0.65 mu m in nominal pore size are tested and are all demonstrated to undergo moderate to severe product retention. Further investigation revealed accumulation of particles in the same size range (approximate to 20-200 nm) as the pores. Based on the assumption that these particles contribute to product retention and membrane plugging, a hollow fiber with an unconventionally larger pore size is subsequently identified and demonstrated to drastically reduce product retention with no impact to cell clarification. Furthermore, these hollow fibers demonstrate surprisingly high membrane capacities, making them an attractive solution to the problem of product retention in perfusion reactors.