Optimisation of Tetrahymena rostrata growth using food by-products as nitrogen source

The composition of media based on yeast extract and nitrogen sources for the growth of Tetrahymena rostrata was optimised by a central composite design. Dairy products promoted better growth than fish powder and starch products and improved generation time of 25% compared to previous reports. The best optimised combination was 5.7 g yeast extract/l + 6.6 g skimmed milk/l which gave the fastest generation time of 122 min and a maximal population of 8.4 X 10(5) cells/ml. In the case of buttermilk, two optimised combinations promoted growth : to induce fast growing (130 min) 2.5 g yeast extract/l + 4.4 g buttermilk/l must be chosen although to improve maximal population (9 X 10(5) cells/ml) 6 g yeast extract/l + 10 g buttermilk/l was more advisable.