ANBI 470.3 Lecture Notes - Lecture 4: Escherichia Coli, Gram-Negative Bacteria, Methionine
20 Jun 2018
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Biotechnology for improvement of feeds: Feed Additives
Organic acids
- wide range from plants and microbial origin
oplant origin: malic, fumaric, sorbic, citric, formic
omicrobial origin: lactic, butyric, propionic, acetic
- many also available as salts
oremove acidic nature of it
- variable anti-microbial against Gram negative bacteria activity
ooften used in combination
Mechanism of action
- site of action in mono gastric animals is the upper level of the GI tract
- organic acids are weak acids so at normal stomach pH most of the acid will be in non-
dissociated
o at low pH most of the organic acids are not charged and so they are able to
freely move across the cell wall of the bacteria
ocharged ones are less capable to move across the membrane
o once inside the bacteria it is a higher pH so they dissociate
o so now the bacteria have to spend more energy pumping out the H+ or the
bacteria will die
oso in low pH they are in non-dissociated form to be able to fuse across the cell
wall of negative gram bacteria then are exposed to pH of 7 and dissociate and
the bug might die or spend more energy pumping out the H+
- how much buffering capacity does a diet have because if lots then the pH goes up and
not so many organic acids go in
- also retention time
- PKa of organic acids is between 3 an 5
- Undissociated form reach bacterial cytosol
- Microbial origin organic acids in ileum and hindgut
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Document Summary
Wide range from plants and microbial origin: plant origin: malic, fumaric, sorbic, citric, formic, microbial origin: lactic, butyric, propionic, acetic. Many also available as salts: remove acidic nature of it variable anti-microbial against gram negative bacteria activity, often used in combination. Pka of organic acids is between 3 an 5. Microbial origin organic acids in ileum and hindgut: propionate and butyrate. Provide fibers that are more readily fermentable can turn down the pathogen gene. Dow regulate spi-1 virulence genes in salmonella: butyrate. Diets that produce lots of this are slowly fermentable diets. Adding organic acids to diets can be expensive and can cause corrosion of metals. Feed inclusion reduces population of e. coli and salmonella in pigs, cattle and poultry. Enterobacteriaceae family can respire anaerobically using nitrate: dissimilatory nitrate reductase. Chlorite accumulates in cell and is toxic. Pre-harvest food safety: diet/water inclusion 24-48 hours prior to slaughter. Fermentation on corn starch, sugar beet molasses etc: l-lysine.
