Sem-2: Water and Food stuffs

Question 1

Vinegar Production

Answer 1

Acetic acid bacteria (acetobacter,gluconobacter)

• very acid tolerant
• aerobic but do not fully oxidise acetic acid to CO2
• process has high O2 demand

Question 2

Vinegar production methods:

Answer 2

• Open-vat (Orleans method)
• trickle method (continuous method)
• bubble method (efficient)

Question 3

Vinegar production methods: Trickle

Answer 3

-Alcohol trickled through wood shavings and aerated from below
-Acetic acid bacteria form biofilm on wood, convert alcohol to acid
-operated continuously
4-5days until desired acid concentration

Question 4

Citric acid production:

Answer 4

Produced by growth of mould Aspergillus niger, in stirred tank fermenter
-low pH,low iron favour citric acid production as a secondary metabolite

Question 5

Citric acid

Answer 5

purified following removal of fungal cells by addition of lime (CaCO)

Question 6

Yeast

Answer 6

• used for baking or nutritional purposes and are grown in aerated fermenters
• cells are recovered from broth by centrifugation

Question 7

Mushrooms -as a food source

Answer 7

• Agaricus bisporus is most common commercially grown species (controlled temp, light, humidity)
• shitake are a commercial mushroom that grow on hardwood logs

Question 8

Vitamins

Answer 8

• production of vitamins second only to antibiotics (sales)
• Vitamin B12 produced by micro-organisms
• deficiency (of B12) results in pernicious anemia
• cobalt is present in b12
• riboflavin can also be produced by microbes

Question 9

Amino acids

Answer 9

• used as feed additives in the food industry
• used as nutritional supplements in nutraceutical industry
• used as starting materials in the chemical industry
• examples include:
• glutamic acid (MSG)
• aspartic acid and phenylalanine (aspartame (nutrasweet))
• lysine (food additives)

Question 10

Drinking water purification

Answer 10

• remove potentially pathogenic micro-organisms
• remove suspended particles, decrease turbidity
• eliminate taste and odour due to organic matter
• reduce nuisance inorganic chemicals (Fe, Mn)

Question 11

Physical methods of water purification

Answer 11

-sedimentation, flocculation/coagulation and filtration

-

Question 12

Chemical methods of water purification

Answer 12

• chlorination
• very effective in removing or killing most pathogens except certain pathogenic protozoa
• cryptosporidium parvum and giardia lamblia fairly resistant to chlorination but should be removed by proper physical methods

Question 13

Testing of water supplies:

Answer 13

• detect indicator organisms

- coliform group are commonly used to indicate presence of faecal pollution

Question 14

Coliforms

Answer 14

• aerobic and facultative aerobic, gram -ve, non-spore forming bacteria that ferment lactose (acid and gas production) within 48h at 35degreesC
• present in intestines

Question 15

Other indicator organisms:

Answer 15

• Faecal streptococci

- Clostridium perfringens

Question 16

Sampling methods

Answer 16

• Multiple tube method

- membrane filtration

Question 17

Water quality as determined by (BOD)mg/L

Answer 17

<2 - unpolluted
3-5 - doubtful
5-10 - poor
>10 - grossly polluted

Question 18

Sewage treatment Standards:

Answer 18

• BOD <25mg/L
• faecal coliforms <5000/100ml
• suspended solids <30mg/L
• involves large-scale use of micro-organisms

Question 19

Sewage disposal

Answer 19

Primary treatment = physical screening and sedimentation

Question 20

Secondary treatment

Answer 20

• aerobic or anaerobic processes
• removes >90% of BOD
• pathogenic bacteria are eliminated
• some viruses may survive

Question 21

Tertiary stage:

Answer 21

chlorination sometimes done

Question 22

Trickling filter system

Answer 22

• sewage sprayed onto bed of crushed rocks about 2cm deep
• bacteria fungi and protozoa form biofilms on the rocks and degrade the organic matter
• these in turn are eaten by predatory protozoa and insect larvae
• complete mineralization of the organic matter to CO2, NH3, NO3, SO4, PO4 takes place

Question 23

Activated sludge system

Answer 23

• sewage is mixed and aerated in large tanks
• slime-forming bacteria e.g. Zoogloea ramigera form flocs, with other bacteria, protozoa, fungi, and oxidize the organic matter
• excess sludge is sent to the anaerobic digestor