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摘要： 266

关键词： computational fluid dynamics   stirred-tank bioreactor   mass transfer coefficient   mixing   population balance model  

摘要： Optimization of a bioreactor design can be an especially challenging process. For instance, testing different bioreactor vessel geometries and different impeller and sparger types, locations, and dimensions can lead to an exceedingly large number of configurations and necessary experiments. Computational fluid dynamics (CFD), therefore, has been widely used to model multiphase flow in stirred-tank bioreactors to minimize the number of optimization experiments. In this study, a multiphase CFD model with population balance equations are used to model gas-liquid mixing, as well as gas bubble distribution, in a 50 L single-use bioreactor vessel. The vessel is the larger chamber in an early prototype of a multichamber bioreactor for mammalian cell culture. The model results are validated with oxygen mass transfer coefficient (k(L)a) measurements within the prototype. The validated model is projected to predict the effect of using ring or pipe spargers of different sizes and the effect of varying the impeller diameter on k(L)a. The simulations show that ring spargers result in a superior k(L)a compared to pipe spargers, with an optimum sparger-to-impeller diameter ratio of 0.8. In addition, larger impellers are shown to improve k(L)a. A correlation of k(L)a is presented as a function of both the reactor geometry (i.e., sparger-to-impeller diameter ratio and impeller-to-vessel diameter ratio) and operating conditions (i.e., Reynolds number and gas flow rate). The resulting correlation can be used to predict k(L)a in a bioreactor and to optimize its design, geometry, and operating conditions.

摘要： 241

摘要： Background: Cell-seeded biomaterial scaffolds have been proposed as a future option for reconstruction of bone tissue. The ability to generate larger, functional volumes of bone has been a challenge that may be addressed through the use of perfusion bioreactors. In this study, the authors investigated use of a tubular perfusion bioreactor system for the growth and differentiation of bone marrow stromal (mesenchymal stem) cells seeded onto fibrin, a highly angiogenic biomaterial. Methods: Cells were encapsulated within fibrin beads and cultured either within a tubular perfusion bioreactor system or statically for up to 14 days. Scaffolds were analyzed for osteogenic differentiation. A rodent cranial defect model (8-mm diameter) was used to assess the bone regeneration of scaffolds cultured in the bioreactor, statically, or used immediately after formation. Immunohistochemistry was used to visualize CD31+ vessel density. Micro-computed tomographic imaging was used to visualize mineral formation within the defect volume. Results: Tubular perfusion bioreactor system-cultured samples showed significantly greater osteodifferentiation, indicated by an increase in VEGF expression and mineral deposition, compared with statically cultured samples. Increased expression of OPN, RUNX2, VEGF, and CD90 was seen over time in both culture methods. After implantation, bioreactor samples exhibited greater bone formation and vessel density compared with all other groups. Analysis of micro-computed tomographic images showed full union formation through the greatest diameter of the defect in all bioreactor samples and the highest levels of mineralized volume after 8 weeks. Conclusion: Mesenchymal stem cells encapsulated in fibrin beads and cultured in the tubular perfusion bioreactor system resulted in increased vascularization and mineralized tissue formation in vivo relative to static culture.

关键词： anaerobic membrane bioreactor   controlled ecological life support system   membrane bioreactor   nitrogen   wastewater treatment  

摘要： A novel wastewater treatment and reuse system (WTRS) combining an anaerobic membrane bioreactor (AnMBR) and an aerobic membrane bioreactor (MBR) with the design capacity of 115 L/d was developed for a terrestrial-based controlled ecological life support system (CELSS). Results clearly showed that the WTRS realized mineralization of organic compounds and reservation of nitrogenous nutrient, therefore converting the effluent into replenishment for the hydroponic system. Trace gas emission from the WTRS could meet requirements for the whole CELSS. Compared with physico-chemical processes, the specific consumables consumption of the WTRS was advantageous but its specific energy consumption is still in need of improvement. Results of microbial community analysis were consistent with the running state of the AnMBR and the MBR.

摘要： 96

关键词： Food waste   Anaerobic   Dynamic membrane   Propionate  

摘要： The applicability of a dynamic membrane (DM) was examined in the anaerobic treatment of high-strength food waste. A DM was established on woven polyester with a pore size of 50 mu m, which achieved a solids retention time to hydraulic retention time ratio of 2.1:12.1. The highest average rate of methane production (1.1 L CH4/L/d) was achieved with an organic loading rate (OLR) of 5.0 g chemical oxygen demand (COD)/L/d. Propionate was the most abundant volatile fatty acid (VFA) for OLRs above 3.1 g/L/d, but concentrations were maintained below 0.9 g/L. Up to 82% of the VFAs in the mixed liquor was reduced in the effluent, implying high metha-nogenic activity of the DM. Microbial assays confirmed a higher archaeal and bacterial content in the DM than in the mixed liquor at shear velocities above 1.0 cm/s. Methanolinea tarda, which is known to be propionate tolerant, was the predominant archaea in the DM.

关键词： cell culture   perfusion   scale-down   screening   semi-continuous  

摘要： Perfusion cell culture, confined traditionally to the production of fragile molecules, is currently gaining broader attention in the biomanufacturing of therapeutic proteins. The development of these processes is made difficult by the limited availability of appropriate scale-down models. This is due to the continuous operation that requires complex control and cell retention capacity. For example, the determination of an optimal perfusion and bleed rate for continuous cell culture is often performed in scale-down bioreactors and requires a substantial amount of time and effort. To increase the experimental throughput and decrease the required workload, a semi-continuous procedure, referred to as the VCDmax (viable cell density) approach, has been developed on the basis of shake tubes (ST) and deepwell plates (96-DWP). Its effectiveness has been demonstrated for 12 different CHO-K1-SV cell lines expressing an IgG1. Further, its reliability has been investigated through proper comparisons with perfusion runs in lab-scale bioreactors. It was found that the volumetric productivity and the CSPRmin (cell specific perfusion rate) determined using the ST and 96-DWP models were successfully (mostly within the experimental error) confirmed in lab-scale bioreactors, which then covered a significant scale-up from the half milliliter to the liter scale. These scale-down models are very useful to design and scale-up optimal bioreactor operating conditions as well as screening for different media and cell lines.

关键词： AnMBR   ZnO-NPs   COD removal   Supernatant characteristics   Microbial community  

摘要： Two laboratory-scale anaerobic membrane bioreactor (AnMBRs) were built to investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on their performance, and the recovery phase was also examined. Results showed that the addition of ZnO-NPs with 0.4 mg/L caused significant deteriorations of AnMBR performance, including decrements of chemical oxygen demand (COD) removal efficiency from 96.4% to 81.5% and biogas production from 0.36 to 0 L/g COD removal within 40 days. A significant increment from 13.2 to 52.1 mg/L in soluble microbial products (SMP) was obtained, while no obvious effect on colloids was observed except an increased fluctuation of colloid concentration. Additionally, gas chromatography-mass spectrometry (GC-MS) analysis revealed remarkable changes of compounds in effluent with exposure to ZnO-NPs, and some new alkanes and esters were produced, such as Cyclobutane, 1,2-diethyl-, trans-, Tetradecane, Cyclopropane, octyl-, and Butanoic acid, methyl ester. The microbial community was compared using high-throughput sequencing, clearly showing the changes in both bacteria and archaea communities. Furthermore, results for recovery phase indicated that the AnMBR performance can be recovered within around 60 days after stopping ZnO-NPs addition, accompanied by the decrement of zinc concentration mainly adsorbed by sludge. (C) 2019 Elsevier Ltd. All rights reserved.

摘要： 262