Ten randomized samples of materials were collected from two places (Damascus, Homs)in Syria for isolation and identification yeasts. These yeasts were classified morphologically according to Barnett's and physiologically by API technique .Results showed that 6 isolated yeasts were Saccharomyces cerevisiae . These isolated yeasts were screened to investigate production of biomass. The results showed that there were differences in the ability of isolated yeasts to produce biomass. Saccharomyces cerevisiae isolated from date fruit was best yeast for biomass production.