Microorganisms

Question 0

Aseptic precautions in fermentation

Answer 0

Filtering the air

Sterilising the fermenter

Question 1

What 2 problems can develop if the inside of the fermenter and the new nutrients are not sterile

Answer 1

1) any bacteria or funghi that managed to get in would compete with the organism in the culture, reducing the yield of product
2) the product would become contaminated with waste products or cells of the ‘foreign’ organism

Question 2

Purpose of water jacket in fermenter

Answer 2

Fermentation produces heat, so prevents contents from overheating and keeps the temperature at the best level for growth (optimum temperature for enzymes)

Question 3

Why do fermenters have to be made of materials which will not corrode

Answer 3

Many microorganisms produce acidic waste products

Question 4

How is the fermenter cleaned

Answer 4

With very hot steam under high pressure

Question 5

Purpose of paddles in fermenter

Answer 5

Mix up contents -> keeps microorganisms in suspension in the liquid, so that they get more exposure to the nutrients, and helps keep the temperature even throughout the vessel

Question 6

Biotechnology

Answer 6

The use of living organisms to make useful chemicals and products or to perform an industrial task

Question 7

Why is it better to sterilise the fermenter with steam rather than disinfectants

Answer 7

Disinfectants are difficult to wash out of the fermenter and might kill the microorganism being grown

Question 8

What process occurs when yeast is added to glucose and oxygen and why is it useful

Answer 8

Aerobic respiration

The carbon dioxide produced is used to make bread rise

Question 9

What process occurs when yeast respites in absence of oxygen

Answer 9

Anaerobic respiration (fermentation)

Question 10

Purpose of malting

Answer 10

Breaking down the starch in barley to sugars so that the yeast cells can ferment it to ethanol

Question 11

Role of amylase in beer production

Answer 11

When barley grains germinate it produces amylase which breaks down the starch into maltose

Question 12

How are barley seeds germinated

Answer 12

By soaking in water and laying them on a flat surface in a malthouse

Question 13

Why is malt ground up and mixed with water in a mash tun

Answer 13

Activates the enzymes to concert starch into maltose

Question 14

Why are hops added to beer

Answer 14

To give it its flavour and stop bacteria growing

Question 15

What happens after the hops and yeast are added

Answer 15

Beer is centrifuged, filtered, and sometimes pasteurised

It is then put into casks or barrels

Question 16

What is yoghurt

Answer 16

Milk that has been fermented by lactic acid bacteria

Question 17

What happens in lactic fermentation

Answer 17

Lactose -> lactic acid

Question 18

Effect of lactic acid on milk

Answer 18

• gives it a low pH which causes milk proteins to denature and curd is formed
• acidic conditions also prevent harmful bacteria from growing

Question 19

Why is milk pasteurised at 85-95*C for 15-30 mins

Answer 19

To kill off any natural bacteria it contains

Question 20

Why is milk homogenised

Answer 20

To disperse the fat molecules

Question 21

Why is milk cooled to 40-45*C before being inoculated with a starter culture of lactic acid bacteria?

Answer 21

It’s the optimum temperature for bacteria

Question 22

What happens when the milk is inoculated with a starter culture of lactic acid bacteria

Answer 22

• bacteria digest milk proteins and ferment lactose to lactic acid
• the pH falls to around 4.4
• the mixture thickens as the drop in pH causes the milk proteins to coagulate

Question 23

Why is the fermenter sterilised

Answer 23

To prevent competition from unwanted organisms and to prevent chemical contamination of product

Question 24

Why is wine no more than 14% alcohol

Answer 24

High concentrations of ethanol kill the yeast cells

Question 25

Why does fermentation eventually stop in yoghurt production

Answer 25

The drop in ph reduces the growth of lactic acid bacteria

Question 26

Making yoghurt is a way of preserving nutrients from milk how?

Answer 26

Low pH prevents growth of ‘spoiling’ microorganisms