The production of carotenoids by the strain of Rhodotorula glutinis, a red soil yeast isolated from IPRAS refinery wastewater, was investigated in a batch system as a function of initial pH, temperature, aeration rate, initial sugar (glucose, molasses sucrose and whey lactose) and ammonium sulphate concentrations and activator (cotton seed oil and Tween 80) addition. Optimum pH and temperature for total carotenoids production were determined as 6 and 30 degrees C, respectively. Total carotenoids concentration and carotenoids production yield significantly enhanced with increasing aeration rate up to 2.4 vvm. An initial ammonium sulphate concentration of 2 g l(-1) gave the maximum carotenoids production. Only the cotton seed oil improved the carotenoids productivity of the yeast considerably at 5 g l(-1) initial glucose concentration. In general, the increase in initial glucose and molasses sucrose concentrations extended the growth of yeast and total carotenoids production while increase in whey lactose concentration did not show the same effect. The highest carotenoid concentration (125.0 mg total carotenoids per liter of fermentation broth) was obtained when 20 g l(-1) molasses sucrose was used as the carbon source while the highest product yield based on the maximum cell concentration (35.5 mg total carotenoids per gram of dry cells) was achieved when 13.2 g l(-1) whey lactose was the carbon source in the broth. (C) 2007 Elsevier B.V. All rights reserved.