Effects of Altering Carbohydrate and Buffer on the Growth of Tehrahymena pyriformis W and on the Determination of the Relative Nutritive Value of Food Proteins

Abstract

Two experiments were conducted to test the effects of carbohydrate source and buffer concentration in the basal media on the growth of T. pyriformis as it relates to the determination of the relative nutritive value (RNV) of food proteins. For Experiment 1, either 0.5, 1.0, 1.5, 2.0 and 2.5% final media concentrations of glucose or dextrin was provided. At all concentrations tested, growth response was greater with dextrin than with glucose. High levels of either carbohydrate source reduced the growth of T. pyriformis. The calculation of RNV was not affected because shifts in growth responses also occurred for the reference standards.For Experiment 2, phosphate buffer concentrations of 2.0, 10.0, 20.0 and 40.0mmoles/liter of medium were included in media containing either glucose or dextrin. T. pyriformis showed consistently higher growth with dextrin than with glucose at all levels of buffer tested. Growth responses at the higher buffer concentrations were reduced relative to responses obtained at lower concentrations. RNV was not affected by treatment. It was concluded that dextrin should be used to replace glucose in the basal media, and that the currently used buffer concentration of 2.0mmoles/liter should be increased five-fold.