Hawkes J J, Limaye M S, Coakley W T
School of Pure and Applied Biology, University of Wales Cardiff, UK.
J Appl Microbiol. 1997 Jan;82(1):39-47. doi: 10.1111/j.1365-2672.1997.tb03295.x.
Continuous flow filtration of suspensions of eukaryotic cells by ultrasonic standing wave enhanced sedimentation has recently been reported. The filtration efficiency for Escherichia coli in such a filter has been characterized at frequencies of 1 and 3 MHz in the present work and compared with results for Saccharomyces cerevisiae. The yeast can be filtered at greater than 99% efficiency at a flow rate of 5 ml min-1 at either frequency. The filtration efficiency of the smaller E. coli at 3 MHz is in excess of 80% at concentrations in the region of 10(10) ml-1 but decreased at lower concentrations. However, E. coli in a mixed suspension with yeast were, because of inter-particle interactions, removed with the filtrate at an efficiency ranging from 80 to 50% over the eight orders of bacterial concentrations tested (down to 10(3) ml-1) at 3 MHz. Quantitative considerations show that poor filtration of pure suspensions of the smaller cells at the lower frequency arises because, at reasonable flow rates, the residence time is not sufficient for the cells to reach the pressure nodal cell concentration regions. The filtration efficiencies of both cell types are comparable at 3 MHz. It is suggested that the more comparable efficiencies arise because concentration regions are narrower at the high frequency and Stokes drag by the filter bulk flow inhibits sedimentation of the concentrated cells.
最近有报道称，通过超声驻波增强沉降对真核细胞悬浮液进行连续流过滤。在本研究中，已对这种过滤器中大肠杆菌在1兆赫和3兆赫频率下的过滤效率进行了表征，并与酿酒酵母的结果进行了比较。在任一频率下，当流速为5毫升/分钟时，酵母的过滤效率可超过99%。在浓度约为10¹⁰个/毫升的区域，较小的大肠杆菌在3兆赫时的过滤效率超过80%，但在较低浓度下会降低。然而，在与酵母的混合悬浮液中，由于颗粒间相互作用，在3兆赫下测试的八个细菌浓度量级（低至10³个/毫升）范围内，大肠杆菌随滤液被去除的效率在80%至50%之间。定量分析表明，在较低频率下较小细胞纯悬浮液的过滤效果不佳是因为，在合理流速下，停留时间不足以使细胞到达压力节点细胞浓缩区域。两种细胞类型在3兆赫时的过滤效率相当。有人认为，效率更具可比性是因为在高频下浓缩区域更窄，并且过滤器整体流动产生的斯托克斯阻力抑制了浓缩细胞的沉降。
