**2.1 Microorganism and cultivation**

*Saccharomyces cerevisiae* PTCC 5269 was supplied by Iranian Research Organization for Science and Technology (Tehran, Iran). The microorganisms were grown at anaerobic condition in an anaerobic jar vessel. The prepared medium for seed culture consisted of glucose, yeast extract, NH4Cl, NaH2PO4, MgSO4 and MnSO4: 10, 3, 0.2, 0.6, 0.2 and 0.05 g.l-1, respectively.

The medium pH was initially adjusted to 6.5 and the inoculums were introduced into the media at ambient temperature. The inoculated cultures were incubated at 30°C. The bacteria were fully grown in a 100ml flask without any agitation for the duration of 24 hours. Substrate consumption was calculated based on determination of the remaining sugars in the culture. Growth was monitored by measuring the optical density (OD at 620nm). Substrate consumption was calculated based on determination of the remained sugars in the culture according to Sadasivam and Manickam(Sadasivam and Manickam, 2005).
