environmental applications and food

Question 1

why and how are microorganisms used in wastewater management

Answer 1

to remove pathogens, man made made chemicals and compounds with high O2 demands. first done with digestion to produce biogas, then the removal of nitrogen (ammonia)

Question 2

what do anammox bacteria do and why is this method favourable

Answer 2

oxidise ammonia to diatomic N and H2O. this method produces less CO2, uses less O2/C and requires less energy

Question 3

where does catabolism happen in anammox bacteria

Answer 3

in the anammoxosome

Question 4

what is a xenobiotic

Answer 4

a synthetic compound with no obvious counterparts in the environment

Question 5

what is bioremediation

Answer 5

using microorganisms to remediate environmental contamination eg Alkanivorax burkemensis which uses alkanes as a substrate and is used in oil spills

Question 6

how are some microorganisms genetically predisposed for degradation

Answer 6

they have catabolic plasmids with genes for important parts of the degradation pathway

Question 7

how are aromatic hydrocarbons eg benzene degraded

Answer 7

first hydroxylation then dehydrogenation to produce catechol. this is then oxidised

Question 8

how does degradation occur anaerobically

Answer 8

FeIII or N are used as the terminal e- acceptor instead of O

Question 9

how do microorganisms recover metals

Answer 9

either by bioleaching from ores or through absorption/accumulation/precipitation

Question 10

how are microorganisms used in food

Answer 10

they can be eaten directly or used to ferment ingredients for new products

Question 11

how is soy sauce made

Answer 11

fungi A. oryzae added to soy beans to make koji. this is then fermented with salt, yeast and bacteria, the harvested

Question 12

how do oxygen levels change in soy sauce production

Answer 12

they are initially aerobic to favour fungi, then later anaerobic to favour yeast and bacteria

Question 13

how does sake production differ to soy sauce

Answer 13

rice is used instead of soy. also added S. cerevisciae to koji to convert the sugar to alcohol

Question 14

whyare microbes selected (domestication)

Answer 14

to prevent the production of aflatoxins due to a loss of biosynthetic and regulatory genes

Question 15

what is added to enable the production of cheese

Answer 15

lactic acid hydrolyses lactose to lactic acid and chymosin hydrolyses casein

Question 16

what domestication is shown in the selection of LAB cultures in cheese production

Answer 16

they have extra plasmids with lactose utilisation genes and have lost other, redundant genes present in wild strains

Question 17

what problems are there in the production of cheese

Answer 17

unstable plasmids and bacteriophage

Question 18

what steps are taken to reduce bacteriophage in cheese production

Answer 18

phage resistant strains are used and regular cleaning

Question 19

how is chymosin produced and what are the three domains

Answer 19

it is now produced by A. niger and contains the pre (export), pro (folding) and chymosin (catalytic) domains

Question 20

how does blue cheese get the blue veins

Answer 20

the addition of P. roqueforti and O2 access allows veins of growth

Question 21

how do enzymes alter the taste and texture of cheese

Answer 21

lipases produce fatty acids and ketones for flavour. proteases influence flavour and texture

Question 22

how is domestication shown in cheese

Answer 22

the same ‘Wallaby’ gene is present in P. roqueforti and P. camemberti but not in wild P. roqueforti. this suggests lateral gene transfer in the food environment

Question 23

how are mycoproteins used for food

Answer 23

they produce low fat, high fibre complete protein from F. venenatum which is produced by continuous air-lift fermentation

Question 24

what are the issues with mycoprotein and how are they overcome

Answer 24

too high RNA (degraded in 64 degree treatment), mycotoxin production (kept in exponential growth phase to avoid this) and variants arising (400hr limit and regulation of pH)