Use of colloid chitin and diatomaceous earth in continuous cake-filtration fermentation to produce creatinase

Abstract

A recombinant Escherichia coli M15(pQE3208) producing creatinase was cultured in a cake-filtration fermentor containing colloid chitin and diatomaceous earth. The filter medium of this cake filtration was a hollow cylinder made of a 20 μm stainless steel sieve located in the centre of the fermentor. During filtration, colloid chitin, diatomaceous earth, and E. coli cells formed a film of filter cake on the 20 μm sieve. The filter cake impeded the outward flow of cells from the fermentor. By controlling the concentration of colloid chitin (3 g/litre), diatomaceous earth (6 g/litre), and the interval of air sparging (0·5 h), continuous cake-filtration fermentation achieved a cell density in the reactor three times higher and specific creatinase activity 35% higher than in ordinary continuous fermentation. An operation mode has been proposed for continuous cake-filtration fermentation to implement the production of intracellular protein which is inversely related to the growth rate of microorganisms.