The present invention relates to a method of and a fermenter for submerged growing of tissue cells on microcarriers.
Growing of tissue cells on carriers, so-called microcarrier-cultures, is known. The carrier on which the tissue cells are grown is composed of very small particles which are maintained in the culture medium in suspension by gentle stirring. The cells grow on the outer surface of this microcarrier in a one-cell layer or monolayer. In accordance with known methods, the microcarrier is sterilized separately in an autoclave or a specially provided carrier, and after this transferred into the fermenter. The aeration during the cultivation is performed as a rule by an aeration ring. The subsequent trypsinization of the culture is carried out in a separate container.
A. L. van Wezel et al., Proc. Biochem. March 1978, starting from page 6, discloses a microcarrier system in which the exchange of the culture medium is performed with the aid of a small sieve filter of high-grade steel with a mesh width of 60.mu., which is mounted in the interior of the fermenter. The culture medium is partially drawn and in this fashion is renewed and recirculated. However, the incorporation of this sieve filter into the fermenter hinders the microcarrier during its discharge from the fermenter. In the event of producing human vaccines, the entire culture medium must be withdrawn, and the cells must be purified serum-free.
A so-called perfusion method is also known in which the medium is continuously exchanged by continuously withdrawing a part of the culture medium via a sieve filter and replacing it with new medium. Such a known sieve filter system operates satisfactorily in the case of small quantities and containers. However it possesses the disadvantage that, in the event it is used for treating greater quantities in which the filter surface is incomparably small relative to the liquid to be separated. As a result of this, the fine-mesh fabric clogs very fast, and a purification and subsequent start can be performed as a rule only after its disassembling. The suspension and mounting of the filter is also very difficult, and an additional opening must be provided in the culture container. Big filter must have a wide mounting location in order to not come into contact with the mixer. Any further inserts offer increased requirements to the sterilization because of dead corners which take place in this case. The known methods also do not permit a residual volume separation.