B) Microorganisms

5.5 Yeast in the production of beer 

• Anaerobic respiration of yeast produces ethanol <-- the basis to alcoholic drinks 
• Glicose ----> alcohol + CO2 + H2O
• Starch breaks down the sugars 
• Beer is largely ethanol, an alcohol molecule 
• Produced from glucose 
• Microorganism that does this is Yeast, it is able to supple the enzymes to bring about the conversion  and that is where the ethanol (alcohol) in beer comes from 
• Ethanol is then flavored by plants to change the flavor 
• The glucose comes from the starch ---------converted-------> maltose ------converted---> glucose 
• Starch broken down by amylase and the maltase broken by  maltose  
• This applies to barley seeds, wheat and rice 
• Starch is broken down into amylase through the germination, process called MALTING, providing us with the sugar needed (glucose) 

5.6 Experiment to investigate CO2 production by yeast in different conditions 

1. Mix 10ml of yeast with 15ml of sucrose 
2. add 5ml of the solution to 5 test tubes (ready to capture gas) 
3. add different amounts of ethanol to each tube 
4. put olive oil on top of the water (to ensure anaerobic conditions) 
5. Heat to 35 degrees in a water bath for 30 mins 
6. Measure the height of the small test tube showing above the solution 

5.7 The production of yoghurt (Lactobacillus) 

• After the milk is pasteurized, the lactobacillus is added 
• The bacteria feeds on the milk releasing lactic acid 
• The acid acts as a preservative 
• The increased pH causes the protein in the milk to come together

5.8 Industrial Fermenter

• Reaction vessel in which fermentation occurs 
• Made out of steel or copper 
• Has an extra steel jacket around it that acts as a cooling jacket 
• Fermentation produces heat so the enzymes must be keeps at a certain temperature to increase the rate of reaction and prevent denaturing 
• There is also a heating plate that can increase the temperature at any time. With the cooling jacket, the temperature can be altered easily to reach its optimum 
• Sterile air (containing oxygen) needs to be pumped in so aerobic respiration can occur, the mixer is there to make sure that the O2 is distributed throughout the chamber 
• Before the reaction, it needs to be sterile, so super heated steam is put into it to kill all bacteria 
• So that fermentation can occur, nutrients have to be added to the tank and will act as food for the microorganism 
• pH probes are also inserted so optimum pH can be controlled to increase the rate of reaction 
• The mixer stirs the reaction to make sure that there are no clumps of substances left and that the microorganism is distributed 

Extra notes 

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