PURPOSE

To produce yeast in a stirred batch fermentor, obtain wet and dry yeast.

THEORY

Producing microorganisms in fermentor is a biotechnological practice. Microorganisms or their products can be obtained to use in field of medical, food etc. Adjusting working conditions like temperature, air volume (O2), pH, stirring speed of the fermentor, a desirable growth of microorganism and production of a metabolite in any scale can be obtained. Yield of fermentor, microorganism and metabolite can be calculated due to stoichiometric equations can be calculated.

Saccaharomyces cerevisiae is an important microorganism in bakery, brewing etc. Its wet and dry forms can be used in different areas. So, there is a developed industry of yeast production.

After production of S. cerevisiae in a medium that is suitable for growth of microorganism in fermentor, biomass should be separated from the medium. Separation can be done different ways like filtration, centrifugation. After separation, to get the biomass as pure, the biomass is washed with distilled water at least 2 times. So ‘cream yeast’ form has been obtained. It is pressed and extruded to increase ratio of dry matter to 30 %. This form of biomass is called ‘wet yeast’. ‘Dry yeast’ form can be obtained by drying up of wet yeast. Its dry matter ratio is 92-94 %. ….