Hint No. 3

About sampling




When using shaken bioreactors sampling obviously involves pausing the shaker. Usually the samples are taken to a clean bench and afterwards the relevant flasks are placed back on the shaker tray.

 

What influence can this sampling procedure have on cultivation conditions?

First, interrupting the shaking causes a rapid drop in the oxygen supply to the culture and this effect increases when transportation and sampling of the flasks takes several minutes. Even if the period of unsaturated oxygen supply is restricted, the metabolism of the cells may switch to “anaerobic conditions” leading to the formation of unwanted by-products and making it difficult to conduct meaningful experiments.

Second, sampling reduces the filling volume. This enhances the oxygen transfer rate in the corresponding flask and means culture conditions in sampled and non-sampled flasks are only comparable to a limited extent.

To avoid these problems it is best to schedule enough flasks so an entire flask can be harvested for each sampling. Also samples should be cooled down immediately after recovery to reduce the metabolic activity of the cells.

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