抄録
This study was conducted to examine the role of chitin-decomposing bacteria on the digestion of chitin in cultured fishes. Chitin-decomposing bacterial counts in the digestive tract contents of red sea bream and Japanese eel fed 0 and 20% chitin supplemented diet were recorded in both diet groups as 102-105 CFU per g and 104-107 CFU per g, respectively. The values were not elevated when chitin was supplemented to the diet. While the bacterial counts in the digestive tract contents of red sea bream decreased extremely when fed diets had two types of antibiotics added to them, the chitinase activities in the tissues of digestive tracts were not changed. Optimum pH of bacterial chitinases isolated from the stomach and intestinal contents of red sea bream were shown to be 6.9 and 7.1, respectively. These values were different from that of chitinase purified from stomach tissue of red sea bream as defined to be 5.5. These results suggest that there may be two types of chitinases which are of bacterial and non-bacterial origins which are involved with digestion in cultured fishes and that the latter plays a more important part.
