Animal cell bioreactors — recent advances and challenges to scale-up

The demand for animal cell derived products has stimulated the development of bioreactors in the last decade. Most of those developments allow a higher cell concentration to be achieved in the bioreactor than in the past, primarily by means of the continuous flow of culture medium and a mechanism of cell retention. The advantages and technological challenges of some of these developments are discussed. Lagging behind the bioreactor developments is the strategy for culture operation and optimization. The need for suitable kinetic models to describe animal cell growth is emphasized.     

Vinyl acetate monomer—a pilot plant study

The kinetics of the reaction of acetic acid and acetylene over zinc acetate-activated carbon catalyst was investigated over a wide range of process variables in a pilot reactor. Although various catalytic reaction mechanisms were postulated, the rate of reaction was most satisfactorily correlated by a mechanism of surface reaction between charged adsorbed acetic acid and acetylene, which assumes that the rate controlling step was the irreversible charged adsorption of acetylene and acetic acid.     

A/O工艺结合高效菌技术处理焦化废水的中试研究

将自行研发的高效菌投加于武钢焦化公司A/O中试装置中,进行生物强化研究。研究结果表明,系统有机物和氨氮去除效果优异,CODcr和氨氮的去除率最高可分别达到95%和97%以上,出水CODcr和氨氮均达到国家一级排放标准。在无需外加碳源的情况下,缺氧池反硝化良好,反硝化率达到50%~73%,缺氧池CODcr脱除率可达到20%~45%。     

Hydrodynamic considerations on optimal design of a three‐phase airlift bioreactor with high solids loading

The hydrodynamic study of a three‐phase airlift (TPAL) bioreactor with an enlarged gas–liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca‐alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal‐loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross‐sectional area ratio (A_D/A_R) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry     

Use of non‐mechanical valves at high temperature—A case study

Non‐mechanical valves are useful devices for controlling the flow of granular solids using only injected. Gas several types of such devices have been described in the literature. In this paper the consequences of using an incorrectly designed L‐valve to move very hot coarse solids from a fluidized bed calciner to a fluidized bed cooler and the steps taken to remedy the situation are described.     

Bioengineered Living Bone Grafts—A Concise Review on Bioreactors and Production Techniques In Vitro

It has been observed that bone fractures carry a risk of high mortality and morbidity. The deployment of a proper bone healing method is essential to achieve the desired success. Over the years, bone tissue engineering (BTE) has appeared to be a very promising approach aimed at restoring bone defects. The main role of the BTE is to apply new, efficient, and functional bone regeneration therapy via a combination of bone scaffolds with cells and/or healing promotive factors (e.g., growth factors and bioactive agents). The modern approach involves also the production of living bone grafts in vitro by long-term culture of cell-seeded biomaterials, often with the use of bioreactors. This review presents the most recent findings concerning biomaterials, cells, and techniques used for the production of living bone grafts under in vitro conditions. Particular attention has been given to features of known bioreactor systems currently used in BTE: perfusion bioreactors, rotating bioreactors, and spinner flask bioreactors. Although bioreactor systems are still characterized by some limitations, they are excellent platforms to form bioengineered living bone grafts in vitro for bone fracture regeneration. Moreover, the review article also describes the types of biomaterials and sources of cells that can be used in BTE as well as the role of three-dimensional bioprinting and pulsed electromagnetic fields in both bone healing and BTE.     

Processing,structure, and mechanical properties of as‐spun polypropylene filaments—A systematic approach using factorial design and statistical analysis

Polypropylene filaments spun under a factorial experimental design were characterized with respect to filament tenacity, elongation, and specific secant modulus. These quantities were assessed quantitatively as responses to seven selected processing parameters using standard statistical methods. It was found that among all the significant factors identified, the draw‐down ratio, which combines metering pump speed (MPS) and filament winding speed (WS), exerts the most significant effects on all the three responses. The grade of polypropylene used, as denoted by its melt flow index (MFI), also significantly influences tenacity and modulus. Spinning temperature, too, influences modulus. In addition, the significant influence of two interaction effects, MPS*WS and MFI*WS, is demonstrated. A further feature of the study is systematic correlation of physical properties with microscopic structure as well as processing conditions. The study has demonstrated that the statistical approach to the development of fiber process technology has the advantages of a one‐step overall design, considerably reduced experimental size, and systematic analysis leading to concise models with known levels of confidence. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 144–154, 2005