The document discusses propionic acid fermentation. Propionic acid is produced through anaerobic fermentation by various bacteria, including Propionibacterium. It has various uses as a preservative in foods and animal therapy. There are challenges to industrial production at scale, including the low growth and productivity of Propionibacterium as well as acid stress. Genetic engineering efforts aim to improve strains' propionate yields, but modification of the high-producing strain P. acidipropionici remains challenging.

1. PROPIONICACIDFERMENTATION
Monday, January 28, 2019 Sir. Stymass Kasty 1

2. INTRODUCTION
Fermentation is the chemical
transformation of organic substances into simpler
compounds by the action of enzymes, complex
organic catalysts, which are produced by
microorganisms such as molds, yeasts, or bacteria.
Fermentation in Food Processing is the
process of converting carbohydrates to alcohol or
Organic acids using Microorganisms such as Yeast
or Bacteria under Anaerobic Conditions.
Necessary Because allows cells to generate ATP without
Oxygen 2

3. INTRODUCTION
3
Propionic acid (CH3-CH3-COOH) is produced by
several anaerobic bacteria among which are the
Coryneform Propionibacterium and Veillonella,
Clostridium and Selenomonas.
 The main Propionic acid fermenters are
Propionibacterium acidipropionici and
Propionibacterium freudenreichii.
Propionibacteria possess cytochromes and catalase
and can tolerate some amount of oxygen.

4. USES OF PROPIONIC ACID
4
IN FOOD INDUSTRY.
Propionic acid and its sodium, calcium
and potassium salts are incorporated to
suppress the growth of mould and rope in
breads and cakes, on the surface of cheese,
malt, fruits, vegetables and tobacco, grain and
silage preservation and to prevent the blowing
of canned frankfurters without affecting their
flavour.
Dipping containers, caps and wrappers in
solutions of these salts is also effective.

5. USES OF PROPIONIC ACID
5
IN FOOD INDUSTRY.
The association of propionic acid with
lactic and acetic acids has been recommended
for the preservative of food.
This recommendation was reinforced by
the works which demonstrated the synergistic
effect of these acids on the inhibition of
Listeria monocytogenes growth in foods.

6. USES OF PROPIONIC ACID
6
IN FOOD INDUSTRY.
The Food and Drug Administration (FDA) lists the
acid, the Na+, Ca++ and K+ salts as preservatives in
their summary of Generally Recognized As Safe
(GRAS) additives and no upper limits are imposed,
except for bread, rolls and cheeses (0.30 to 0.38%).
The strain Propionibacterium subsp.
Chermanii is used in Cheese making to create CO2
bubbles that become “Eyes” (Round holes in the cheese)
Propionate is metabolized like other fatty acids in
the mammalian body

7. USES OF PROPIONIC ACID
7
IN ANIMAL THERAPY
Sodium propionate has been used in:
 Wound infections
 Dermatoses (Antifungal agents)
 Anti-arthritic drugs and
 Conjunctivitis

8. USES OF PROPIONIC ACID
8
OTHER USES
 Production of Cellulose plastics
Used in textile, filters, reverse osmosis
membranes, lacquer formulations and molding plastics.
 Used as Herbicides
 Used in the manufacture of Ester solvents and fruit
flavors. Example, Citronellyl propionate and Geranyl
propionate.
 Perfume bases and Butyl rubber to improve
processability and scorching resistance.

9. MIXED-ACID FERMENTATION
9
 The Biological process by which a six-carbon
sugar like Glucose is converted in to a complex
and variable mixture of acids
 These fermentations generally generate Acids
such as Acetic acid, lactic acid and succinic acid.
 Sometimes also generate neutral products such
as Butanediol
 These are the characteristics of most members of
Enterobacteriaceae

10. PROPIONIC ACID FERMENTATION
10
The first works on propionic acid
fermentation resulted in the formulation of the
Fitz equation:
3 lactic acid ------> 2 propionic acid + 1
acetic acid + 1 CO2 + 1 H20
OR
1.5 glucose ------> 2 propionic acid + 1 acetic
acid + 1 CO2 + 1 H20

11. PROPIONIC ACID FERMENTATION
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Theoretical maximum yields are 54.8% (w/w) as propionic
acid and 77% as total acids.
Formation of propionic acid is accompanied by the formation
of acetate for stoichiometric reasons and to maintain hydrogen and
redox balances.
Propionibacteria have been the primary candidates for the
development of a biological process due to their unique metabolism.
Dairy species such as P. acidipropionici strains, have been
explored as potential propionic acid producers due to their
tendency to produce propionate at a higher titre and yield.
Propionibacterium uses Wood-Werkman cycle to
produce propionate. Wood-Werkman cycle is energetically the most
efficient propionate fermentation route currently known.

12. PROPIONIBACTERIUM
 Gram-positive
 Facultative Anaerobic
 Non-sporulating
 Rod shaped
 Facultative parasites and
Commensals of human and
other animals
 Living in and around the
Sweat glands, Sebaceous
glands and other areas of
the skin.
 They may cause Acne (p. acnes)
 Selective media for their
Growth is Sodium Lactate
 Members of the Genus
Propionibacerium
are widely used in:
i. Production of
Vitamin B12
ii. Tetrapyrrole
compounds
iii. Probiotic and Cheese
industries
iv. PROPIONIC ACID
PRODUCTION
12

13. PROPIONIC ACID
FERMENTATION
PATHWAY
o Pyruvate reacts
with methyl
malonyl coA to
form Propionyl coA
and Oxaloacetate.
o Oxaloacetate
give rise to malate,
fumarate and
succinate by
reverse TCA cycle.
o Propionyl coA
transfer its coA to
succinate to form
succinylcoA and
propionate.
13

14. THE PROPIONIC ACID FERMENTATION OF
PROPIONIBACTERIUM
14

15. 15

16. PROPIONIC ACID FERMENTATION ROUTES
16
B. DEGRADATION OF AMINO ACIDS TO PRODUCE
PROPIONATE.
This involves the degradation of Valine,
Threonine, Isoleucine and Methionine.
These can lead to the production of Propionate and ATP
via Propionyl-CoA.
Escherichia coli has been engineered to produce
high yield of Propionyl-CoA.
The combination of the Valine or Isoleucine and
Threonine Pathways are synergistic given the redox
and energy balances and can, together improve the
propionate yield

17. 17

18. 18

19. SCHEMATIC FLOW SHEET DIAGRAM OF
THE PROCESS
cells are
from the
and recycled
The
separated
medium
back to the bioreactor
using an ultrafiltration
unit (UF Unit)
It relies on the
Continuous production
of Propionic acid by
increasing the Viable
Cells to the bioreactor
rather than Batch
Fermentation 24

20. INDUSTRIAL PROPIONIC ACID
PRODUCTION
20

21. CHALLENGES FOR INDUSTRIAL
PROPIONIC ACID PRODUCTION
21
Culturing Propionibacterium is
limited to:
 Low growth rates
 Low productivities
 Acid stress and
 The co-generation of by-products which
increase downstream processing costs and
limit the economic feasibility of the
fermentation process.

22. CHALLENGES FOR INDUSTRIAL
PROPIONIC ACID PRODUCTION
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Targeted genetic engineering of
propionibacteria to increase the production of
propionate remain challenging because of different
reasons.
I. Propionibacteria have high GC content, which
complicates genetic manipulation and
contributes to poor gene annotations.
II. There are few closed genomes and a small
number of cloning vectors are available.

23. CHALLENGES FOR INDUSTRIAL
PROPIONIC ACID PRODUCTION
23
III.The ability of strains to readily develop spontaneous
antibiotic resistance.
IV.Presence of strong restriction modification systems
which contribute to the low transformation efficiency of
propionibacteria
But,
A number of recent studies have reported the
modification of P. freudenreichii subsp. shermanii (P.
shermanii) and P. jensenii while only a couple of
contentious studies have reported modification of the
high-producing, genetic modification resistant strain, P.
acidipropionici

24. CHALLENGES FOR INDUSTRIAL
PROPIONIC ACID PRODUCTION
According to R.A.G.Garcia et al (2017), “The
expression of methylation components of restriction
modification systems in host organisms has resulted in large
improvements in the transformation efficiencies of non-model
organisms and may be a critical step to improving the
transformation efficiency in propionibacteria, particularly
P. acidipropionici. Despite promising progress in the rational
design of P. shermanii and P. jensenii, these modified
strains still fall short of the natively high-producing
P. acidipropionici.
Therefore, a second line of research has focussed on
random-mutagenesis strategies to enhance propionic acid
production in P. acidipropionici.”
Monday, January 28, 2019 Sir. Stymass Kasty 29

25. CONCLUSION
25
Propionic acids and their salts have
many uses in different fields of
Biotechnology apart from Food Industries,
therefore there is a need of increasing the
production of Propionate by taking the
advantage of all non-pathogenic Bacteria
which are capable of ferment different
substances such as Sugar, Amino acid and
others to produce large amount of
Propionate.