GROWTH-PARAMETERS FOR THE YEAST RHODOTORULA-RUBRA GROWN IN PEAT EXTRACTS

A newly-isolated strain of Rhodotorula rubra, which has been reported to have the ability to synthesize high concentrations of carotenoids, has been adapted and grown in liquid phase using acid extracts of peat as the main substrate source. The growth of the yeast was studied as a function of the medium carbohydrate concentration, pH, time, temperature, and agitation rate. The optimal growth conditions were found to be an initial total carbohydrate concentration of 15 g.l-1, a pH of 5.5, an incubation time of 3.5 d, a temperature of 22-degrees-C, and an agitation rate of 200 rpm. Under those conditions, the growth parameters were: approximately 4.8 g.l-1 dry biomass, 70% yield and 32% efficiency. Also, a total beta-carotene concentration of 1,256 mug.g-1 dry biomass was produced by the yeast.