Microbial fermentation

Question 1

Fermentation is …?

Answer 1

Anaerobic digestion of substrates by bacteria & other microorganisms

Question 2

Fermentative digestion enzymes are ___ in origin

Answer 2

microbial

Question 3

Difference between fermentative & glandular digestion

Answer 3

Fermentative = SLOWER

Question 4

Requirements for proper fermentation?

Answer 4

Temp = 37 degrees
pH buffered
Osmolality optimum
Suitable substrate (CHO)
Indigestible material removed
Rate of removal = regeneration time of favourable microbes
VFAs removed or buffered

Question 5

Major food sources for fermentation for large herbivores?

Answer 5

Forages/foliage of plants

Question 6

Glue cellulose together?

Answer 6

Hemicellulose, lignin, pectin

Question 7

CHO digestion involves which 3 plant CHOs?

Answer 7

Insoluble structural polysaccharides (cellulose, hemicellulose)
Soluble structural polysaccharides (gels - pectins)
Storage mono-, oligo-, polysaccharides (starch)

Question 8

Function of the rumen?

Answer 8

Large, anaerobic fermentation vat
Soluble products mostly absorbed thru wall
Material leaving RR = food residues, bacteria, protozoa, (+soluble fermentation end products)

Question 9

Fermentation microbes are mainly?

Answer 9

Fungi
Bacteria
Methanogens
Mycoplasms
Phages (viruses)
At least 28 important spp

Question 10

A bit about fungi…?

Answer 10

Anaerobes
Survive completely on ingested feed
Able to digest cellulose, starch etc
1st organism to attack & start digesting structural plant components
Not numerous, but take 1st bite

Question 11

A bit on rumen bacteria..?

Answer 11

Most are strict anaerobes
10^10 bacteria/g ingesta
Synthesis microbial protein
Wide range >200 spp. 
Pop. needs time to adapt to change in diet

Question 12

Rate of bacterial population depends on?

Answer 12

Available energy
Bacterial turnover time
Limited by cellulose digestion
Limited by starch storage by protozoa

Question 13

Bacterial growth requires…?

Answer 13

Fermentable CHOs
N for protein synthesis (ie ammonia, AAs, urea or peptides)
Other micronutrients (sulphur)

Question 14

Rumen bacteria & substrates are…? Give egs

Answer 14

Widely adapted (Lactobacilli/butyrivibrio)
Digest cellulose & hemicellulose (Ruminococcus)
Digest starch (streptococcus bovis)

Question 15

Properties of methanogens…?

Answer 15

CH4 (methane) producing archea
Similar to bacteria
Produce methane as end product of feed in rumen

Question 16

Example of methanogens?

Answer 16

Methanobrevibacter

Question 17

Protozoa properties?

Answer 17

Much larger than bacteria
Fewer in number
Increase with [starch]
Feed on bacteria

Question 18

Define defaunation

Answer 18

removal of protozoa -> increase bacteria -> increase bacterial protein-N -> decrease ruminal [NH3]

Question 19

Most important protozoa?

Answer 19

Anaerobic ciliates

Question 20

2 families of protozoa & apperance?

Answer 20

Holotrich - ‘hairy’ covered by cilia

Entodiniomorphid - ‘tufted’ most of body naked except tufts/patches of cilia

Question 21

Holotrichs properties…?

Answer 21

Use starch & sugars
Associated with feed particles
Do not readily pass from rumen
Store sugars

Question 22

Fermentation end products of holotrichs?

Answer 22

Acetic acid
Butyric acid
Lactic acid
H2 gas

Question 23

Entodiniomorphs properties…?

Answer 23

10 genera
Ingest starch, plant material, bacteria
Digest cellulose/hemicellulose
Increase in no. when animal eats grain diet

Question 24

Mycoplasms properties…?

Answer 24

Smallest bacteria
Cell membrane NOT cell wall
~10^6/g ruminal contents (sheep/cattle)
Important in maintaining balanced ecosystem
Provide energy for ruminants

Question 25

Bacteriophages (viruses) properties…?

Answer 25

Can burst open other microbes
Lyse bacterial hosts
Involved in protein recycling
Possibly beneficial