Extrazelluläre Chitindeacetylase mariner und terrestrischer Bakterien

Abstract

The aim of this work was to find a bacterial catabolic enzyme, suitable for the deacetylation of chitin to chitosan. This enzyme, called chitin deacetylase, is known to be present in fungi but not in bacteria. To find such an enzyme we first had to isolate bacteria which are able to grow on chitin.From marine sediments and also from compost, enriched with chitin, several bacteria strains were isolated on chitin plates or on acetate, the second product of a chitin deacetylase besides chitosan.Some of the strains were tested for chitin deacetylase activity with a colorimetric test or with a test for the formation of acetate. Regarding the advantages of an extracellular enzyme for a technical process (the purification of the enzyme is easier), the screening methods were designed to detect extracellular enzymatic activity in the culture media. A few strains had chitin deacetylating activity but the best results were those of strain 99.6. This strain had also a chitinase activity. The cda-encoding gene of this strain was cloned into E.coli at the Fraunhofer Institute in Hannover.First investigations with 99.6 were done to optimize the culture conditions for a technical process. We also tried to reduce chitinase activity by UV-induced mutations. But after this, also the deacetylating activity was much lower. Trying to concentrate the ezyme we recognized that the enzyme is very unstable. Most of its activity was lost during centrifugation or freezing.