Water extracts of cabbage, watermelon, a mixture of residual biomass of green salads and tropical fruits were used for yeast cultivation. These extracts contained from 1420 to 8900 mg/l of dissolved organic matter. and from 600 to 1800 mg/l of nitrogen. pH of the extracts was in the range from 4.1 to 6.4. Biomass concentration of yeast. Saccharomyces cerevisiae. CEE 12 grown at 30 degreesC for 96 h in the sterilized extracts without any nutrient supplements was from 6.4 to 8.2 g/l; content of protein was from 40% to 45% of dry biomass. The yield was comparable with the yield of yeast biomass grown in potato dextrose broth. The biomass can be. considered as the protein source. Its feed value was enhanced by incorporation of selenium in biomass to the level of 150 mug/g of dry biomass. Therefore it was. recommended to transform the extracts from vegetable and fruit processing wastes into the yeast biomass enriched with selenium. (C) 2004 Elsevier Ltd. All rights reserved.