L3: Microbial Fermentation Flashcards
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
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)
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
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.
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
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
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
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
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
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
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
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
List the substrates of fermentative digestion
Examples:
Name the bacteria that have a wide range of substrates
- Butyrivibrio spp
- Selenomas spp
- Lactobacilli spp
List the substrates of fermentative digestion
Examples:
Name the bacteria that digest cellulose & hemicellulose
- Bacteriodes succinogens
- Ruminococcus spp
List the substrates of fermentative digestion
Examples:
Name the bacteria that digest starch
- Bacteriodes amylophilus
- Streptococcus bovis
