‎Fermentation Lab Sheets‎ > ‎Production of Yeast ( FE 411 )


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


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 %. ….

Fermentation Lab Sheets‎ > Vinegar ( FE 411 )


To practice slow and fast process of vinegar, to measure some parameters of the vinegar.


Vinegar is a fermented solution that contains acetic acid. Vinegars contain some other acids like citric acid, tartaric acid besides acetic acid. Vinegar products don’t have a time limitation for shelf-life due to it’s stability. Vinegar is basically used as a flavor. Because of it’s acetic acid content (4-6 %), it preserves the foods. Also, it is a color stabilizer and cleaning agent.

Fermentation Lab Sheets‎ > ‎White Cheese ( FE 411 )


To practice making white cheese.


Cheese is a fermented milk product. Milk protein=casein is coagulated by rennet and milk sugar=lactose is fermented by cheese culture. Then whey is seperated and solid part=cheese is obtained. There are many types of cheese according to properties of milk, production technique, ripening technique and variety of starter culture.

Properties of milk are important. Generally in raw milk:

1. Amount of protein (especially amount of casein) should be at a high level.

2. Fat and dry matter ratios should be at normal levels.

3. Total microorganism burden should be lowly.

4. There shouldn’t be any kind of inhibitor material like antibiotic, disinfectant etc.

5. Coagulation test with enzyme should be positive.

Procedure techniques are changable with regard to type of cheese. There are several coagulation; acid coagulation, heat coagulation, enzyme coagulation, crystallization, concentration or combination of two coagulation type.