Production of secreted hydrolytic enzymes by continuous high-cell-density cultivation of Colpidium campylum

Abstract

The aim of the present study was to test the suitability of the ciliated protozoon Colpidium campylum for axenic high-cell-density fermentation and for production of acid hydrolases. Subsequent to an initial batch fermentation with generation times of 12.4 h, the culture medium was exchanged continuously by means of a perfusion module made of polypropylene hollow fibres. The same technique was used for harvesting the secreted enzymes. With the cells being retained completely, the stationary phase could be maintained for 33 days, reaching a maximal cell density of 1.15 × 106 cells ml–1 and a dry weight of 8.7 g l–1. Protease, acid phosphatase, β-N-acetylhexosaminidase, α-mannosidase, α- and β-glucosidase were secreted in high amounts into the spent medium, but only low activities of α- and β-galactosidase were detected. The latter observation corresponds with an almost stable concentration of lactose in the culture broth, indicating that this disaccharide is neither broken down nor taken up by C. campylum. In contrast, glucose and nutritional protein were consumed completely during the first phase of fermentation. The data provide evidence that enzyme secretion is more widely distributed among holotrich ciliates than generally assumed and that Colpidium campylum might be considered as a suitable new source for production of enzymes useful in biocatalysis.