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.     

Scale-up of liquid-liquid dispersions in stirred tanks

A study of local drop size, drop size distribution and holdup fraction was conducted for liquid-liquid dispersions in three geometrically similar stirred tanks of standard configuration over a range of stirrer speeds and dispersed phase volume fractions. The tanks had diameter ratios 1:2:4, the smallest diameter being 11 cm. Two liquid-liquid systems were used: n-heptane-water and n-heptane containing different concentrations of di-(2-ethylhexyl) phosphoric acid dispersed in an aqueous sulphate solution. No significant local variations of the three parameters investigated were observed at constant stirrer speed and constant dispersed phase volume fraction. Measurements in the three tanks indicated that the rule of equal impeller tip speed provides the best scale-up criterion for equal interfacial areas per unit volume of dispersion. A correlation was also proposed for the Sauter mean diameter.     

Scale-up of a cyclone bioreactor

The operation of a cyclone bioreactor differs from conventional stirred tanks since the agitation is accomplished by means of a pumped reciculation loop. Oxygen transfer can occur across the swirling gas—liquid interface in the cyclone or from bubbles entrained in the recirculation loop. A cyclone bioreactor was scaled-up from a 1 dm³ bench top unit to a 75 dm³ Process Development Unit (PDU). A reduction in the aspect ratio was compensated for by extending the length of the recirculation loop and providing additional aeration. Performance of the two reactors for the production of microbial poly-β-hydroxybutyrate (PHB) was compared under various operation conditions. The culture used for PHB production was Alcaligenes eutrophus DSM 545, grown on a mineral salts medium limited by the supply of nitrogen. The levels of dissolved oxygen obtained in the PDU were strongly dependent on the location at which the air was introduced into the reactor. However, with aeration balanced between two injection points and a similar level of power input, 17 J s^?1 dm^?3, the PDU was able to provide at least as much oxygen transfer capability as the laboratory-scale reactor. Under all conditions tested, the PHB accumulation by A. eutrophus was in excess of 80% of the biomass dry weight, although the yield on glucose was lower in the PDU than in the laboratory-scale reactor.     

Some aspects of electrochemical engineering

After a short discussion of the concept of electrochemical engineering, the immediate history of electrochemical process engineering (EPE) is briefly mentioned. Topics then considered are electrolytic reactor design, process modelling and optimisation, and the development and scale-up of electroorganic processes. The article concludes with an assessment of the present state of EPE.     

船闸新型浮式系船柱的设计与应用

针对国内船闸浮式系船柱普遍存在系缆高度偏低、导轮支架易变形等问题,以湘江长沙综合枢纽船闸中的浮式系船柱为研究对象,介绍了一种船闸新型浮式系船柱的设计与应用。在不改变浮式系船柱门槽尺寸的情况下,改变新型浮式系船柱的浮筒材料,将系船架结构调整为系缆小车结构,调整导轮支架,解决了原浮式系船柱系缆高度偏低、结构自重大、小车架导轮支架强度偏小等问题。经改造后,新型浮式系船柱应用效果良好,可为类似船闸浮式系船柱的改造和应用提供参考和借鉴。     

液体搅拌的放大

介绍了几种常用的液体搅拌放大的判据,并对流量型搅拌、气液分散、液液分散、固液悬浮以及结晶过程的搅拌,分别提出了适用的放大判据。对于几何学条件,有的可以是几何相似的,有的则不能采用几何相似。还讨论了以单位容积功率作为放大判据时,可能出现的问题和改进措施。     

气-液-固滴流床反应器放大中的重要参数及其数学模型

介绍了在滴流床反应器放大过程中所涉及到的物理化学参数和数学模型建立的方法，并对这些参数计算的经验公式进行了综述，为滴流床反应器的模拟、放大提供了理论依据。     

某含钴氧化铜矿选矿试验研究

某含钴氧化型铜矿含铜3.22%、含钴0.045%, 采用先浮硫化矿后浮氧化矿原则流程, 进行了实验室验证试验及扩大连选试验研究。实验室验证试验获得了铜品位51.52%、钴品位0.138%的硫化铜精矿和铜品位19.53%、钴品位0.437%的氧化铜精矿; 扩大连选试验获得了铜品位45.11%、钴品位0.154%的硫化铜精矿和铜品位12.31%、钴品位0.261%的氧化铜精矿; 铜总回收率大于80%, 钴总回收率大于55%。研究成果可为该矿石工业应用工程设计提供依据。