Developing an ultra-intensified fed-batch cell culture process with greatly improved performance and productivity.

Intensified fed-batch (IFB), a popular cell culture intensification strategy, has been widely used for productivity improvement through high density inoculation followed by fed-batch cultivation. However, such an intensification strategy may counterproductively induce rapidly progressing cell apoptosis and difficult-to-sustain productivity. To improve culture performance, we developed a novel cell culture process intermittent-perfusion fed-batch (IPFB) which incorporates one single or multiple cycles of intermittent perfusion during an IFB process for better sustained cellular and metabolic behaviors and notably improved productivity. Unlike continuous perfusion or other semi-continuous processes such as hybrid perfusion fed-batch with only early-stage perfusion, IPFB applies limited times of intermittent perfusion in the mid-to-late stage of production and still inherits bolus feedings on nonperfusion days as in a fed-batch culture. Compared to IFB, an average titer increase of ~45% was obtained in eight recombinant CHO cell lines studied. Beyond IPFB, ultra-intensified IPFB (UI-IPFB) was designed with a markedly elevated seeding density of 20-80 × 106 cell/mL, achieved through the conventional alternating tangential flow filtration (ATF) perfusion expansion followed with a cell culture concentration step using the same ATF system. With UI-IPFB, up to ~6 folds of traditional fed-batch and ~3 folds of IFB productivity were achieved. Furthermore, the application grounded in these two novel processes showed broad-based feasibility in multiple cell lines and products of interest, and was proven to be effective in cost of goods reduction and readily scalable to a larger scale in existing facilities.

[Variations and influencing factors of nitrate nitrogen concentration in water in a small watershed of Three Gorges area].

In order to study the water quality and response to influencing factors in typical watersheds of Three Gorges area between 2004 and 2005, the variation characteristics of nitrate nitrogen concentration were analyzed under heterogeneous landscape condition through continuous observation with method of dividing into sub-watersheds in Quxi watershed (the first-grade branch, located in Three Gorges). The results suggested that nitrate nitrogen concentration fluctuated between 0.4 and 14.6 mg x L(-1) with the highest in winter,higher in autumn and summer and lower in spring. Discrepancy also exists in different years. In addition, nitrate nitrogen concentration shows increasing trends with the aggravating impacts of agricultural activities on environment. Moreover, nitrate nitrogen concentration had some relationships with different land use types and space layout to some extent, and was also affected by geological and hydrological characters in the sub-watersheds, which indicated that response of nitrate nitrogen concentration in water was evident to influencing factors.