L3: Microbial Fermentation Flashcards Preview

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Flashcards in L3: Microbial Fermentation Deck (17)
1

Describe the differences b/w non-fermentative & fermentative digestion

Enzymatic hydrolysis of lrg molecules is essential for both fermentative & glandular digestion BUT fermentative enzymes are MICROBIAL in origin -fermentative rate of rxns slower -extent of alteration to lrg molecules greater

2

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

List the requiremenrs for proper fermentation

  • Anaerobic conditions
  • Temp 39˚C
  • pH 6.0 - 6.7 (neutral)
  • Ionic strength in optimum range (~300mOsm)
  • Suitable substrate (CHD)
  • Regular turnover of digesta in/out, mean retention time (MRT)
  • Rate of microbe removal = rate of microbe regeneration
  • VFA produced removed (toxic)
  • Contents well & continuously mixed (contractions)

3

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

Describe rumen fungi & bacteria

  • FUNGI
    -obligate anaerobes 
    -survive totally on ingested feed
    -digest structural plant polysaccherides (cellulose, starch, hemicelluloses)
  • BACTERIA
    -strict anaerobes (die in presence of O2)
    -synthesise microbial (bacterial) protein
    -Spp. present & relative numbers in rumen change greatly w/ feed composition & dietary changes

4

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

Describe methanogens

  • CH4 producing archaea
  • Produce CH4 as an end product of microbial digestion of feed in rumen
  • Larger and more diverse range found in forage-fed than grain-fed
  • methanobacterium ruminantium
  • methanobrevibacter sp.

5

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

Describe rumen protozoa

  • < number than bacteria but = biomass
  • > numbers w/ > starch [ ] 
  • < methane production
  • Removal if called defaunation = > bacteria, so > flow of bacterial protein-N from rumen
  • Two families:
    -Holotrich (hairy) => use starch & soluble sugars, store sugars, fermentation end products are: acetic, butyric, lactic acids
    -Entodiniomorphid (tufted) => ingest starch, plant material, bacteria

6

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

Describe mycoplasmas

  • Little known importance
  • associated w/ respiratory, urinary & gastro disease
  • lysis of bacterial & fungal cell walls

7

Describe the different groups of rumen microbes & how the rumen provides an ideal enviro for fermentative digestion

Describe bacteriophages (viruses)

  • Destroy other microbes
  • involved in protein recycling

8

Summarise the process of microbial fermentation & growth

What does rate of growth of bacterial popn depend on?

  • Amount of e available (substrate)
  • Bacterial turn over time 
  • Number of initial cellulose fermenters
  • Individual bacteria spp.
  • type & amount of inoculant

9

Summarise the process of microbial fermentation & growth

What does bacterial growth require a constant supply of? Draw diagram representing process of fermentation & growth

  • Requires constant supply of fermentable CHD for energy (substrates), some form of N for protein synthesis

 

10

List the substrates of fermentative digestion

Plant cell walls are complex CHD molecules.

More cell wall =?

  • < digestibility
  • > fermentation
  • loss of energy
  • < microbial production
  • < VFA production
  • < protein

11

List the substrates of fermentative digestion

CHD digestion involves 3 groups of plants CHD's. Describe.

  • Storage mono-, oligo- & polysaccherides
    -starch, fructans, water-soluble CHD
    -Easily digested
  • Soluble structural polysaccherides
    -gels
    -pectins, B-glucans
  • Insoluble structural polysaccherides
    -cellulose, hemicellulose
    -Fermentation

12

List the substrates of fermentative digestion

What is the limiting factor of digestion of plant CHD?

  • LIGNIN 
    -part of cell wall but not a CHD
    -Indigestible

13

List the substrates of fermentative digestion

Examples:

Name the bacteria that have a wide range of substrates

  • Butyrivibrio spp
  • Selenomas spp
  • Lactobacilli spp

14

List the substrates of fermentative digestion

Examples:

Name the bacteria that digest cellulose & hemicellulose

  • Bacteriodes succinogens
  • Ruminococcus spp

15

List the substrates of fermentative digestion

Examples:

Name the bacteria that digest starch

  • Bacteriodes amylophilus
  • Streptococcus bovis

16

List the substrates of fermentative digestion

Examples:

Name the bacteria that digest mono & di saccherides

  • Succinovibrio dextrinosolvens
  • Eubacterium
  • Lactobacilli

17

List the substrates of fermentative digestion

Examples:

Name the bacteria that digest lactate & simple sugars

  • Peptostreptococcus elsdenii
  • Selenomonas lactylitica