Russotti G, Osawa A E, Sitrin R D, Buckland B C, Adams W R, Lee S S
Merck and Co., Inc., Merck Research Laboratories, Bioprocess R&D, Rahway, NJ 07065, USA.
J Biotechnol. 1995 Oct 16;42(3):235-46. doi: 10.1016/0168-1656(95)00083-3.
In order to develop a cost-effective recovery process for an intracellular product, crossflow microfiltration was studied for the harvest of a recombinant yeast under severe time constraint. It was required to process yeast broth in a short period of time to minimize the risk for product degradation. Preliminary microfiltration studies employing flat sheet membranes showed high throughout with initial fluxes on the order of water fluxes (> 1000 LMH, regime I, < 2 min), followed by a rapid decay towards a low pseudo-steady state flux (20 LMH, regime II, > 2 min). Exploitation of these high fluxes and control of their eventual decline were crucial in establishing a rapid crossflow filtration process. The effect of several parameters, such as initial cell concentration, shear rate, transmembrane pressure, membrane pore size and medium composition on filtration performance were investigated to better understand the flux decline mechanisms. We found that the major contributor to flux decay was reversible fouling by the cake formation on the membrane surface. Within the operating boundaries of our microfiltration system, large-pore membrane (0.65 micron) was much more desirable for harvesting our yeast (10 microns size) without cell leakage than smaller pore ones (0.22 micron and 0.45 micron). Among adjustable operating parameters, feed flow rate (i.e., shear rate) exerted significant impact on average flux, whereas manipulation of transmembrane pressure afforded little improvement. Although initial cell concentration affected adversely the permeation rates, growth medium components, especially soy-peptone, was deemed pivotal in determining the characteristics of cell cake, thus controlling yeast microfiltration.
为了开发一种具有成本效益的细胞内产物回收工艺，在时间紧迫的情况下，对错流微滤用于收获重组酵母进行了研究。需要在短时间内处理酵母发酵液，以将产物降解风险降至最低。采用平板膜的初步微滤研究表明，通量很高，初始通量与水通量相当（>1000 LMH，阶段I，<2分钟），随后迅速衰减至低伪稳态通量（20 LMH，阶段II，>2分钟）。利用这些高通量并控制其最终下降对于建立快速错流过滤工艺至关重要。研究了几个参数，如初始细胞浓度、剪切速率、跨膜压力、膜孔径和培养基组成对过滤性能的影响，以更好地理解通量下降机制。我们发现通量衰减的主要原因是膜表面形成滤饼导致的可逆污染。在我们的微滤系统操作范围内，大孔膜（0.65微米）比小孔径膜（0.22微米和0.45微米）更适合收获我们的酵母（大小为10微米）而不会发生细胞泄漏。在可调节的操作参数中，进料流速（即剪切速率）对平均通量有显著影响，而调节跨膜压力几乎没有改善。虽然初始细胞浓度对渗透速率有不利影响，但生长培养基成分，尤其是大豆蛋白胨，被认为在决定细胞滤饼特性从而控制酵母微滤方面起着关键作用。
