ABOUT Acetone butanol fermentation

1. Acetone-Butanol Fermentation

2.  Introduction:
 Pasteur first noted this fermentation in 19th
centuy.
 In 1916 Chaim Weizmann develoed this process
using C. acetobutylicum so till today known as
Wezmann process.
 Before first world
warButanolButadieneSynthetic rubber. So
interest was butanol fermentation.
 Later interest was moved to acetone as it was
used to produce explosive TNT during world war.

3.  After world war II fermentation was replaced with
petroleum based process.
 Majority of plants with less than 200m3 capacity were
closed.
 Some plants are still running where economic,
political, geographical and climatic factors are
favourable.
 Major products of fermentations are: Butyric acid,
butanol, isopropanol, ethanol and acetone, produced
from starch, molasses, sucrose, wood molasses etc.

4.  Microbial strains and products:
 Clostridium acetobutylicum: Acetone/Butanol
fermentation
 Clostridium butylicum: Butanol/isopropanol
fermentation
 Clostridium butyricum: Butyric acid/acetic acid
fermentation

5. Biosynthesis:
 Along with n-Butanol H2 and CO2 are also
produced.
 In addition ethanol can be produced
through reduction of acetaldehyde.
 Butanol at a conc. of less than 0.5% has no
influence on the cells, where as at higher
concentration it causes damage to
phospholipids of cell membrane and at
conc. Above 1.3% butanol production
ceases.
 Some strains produce autolysins and die

8. Production process
 Few plants are still working in Souh Africa.
 Stock cultures of Clostridium acetobutylicum are stored as
spores in sand for up to 30 years.
 Although production fermenter is inoculated with low inoculum
ratio, that is 1:3000, but inoculum is prepared over in several
stages because it has following advantages.
1. Greater resistance to contamination
2. Shorter fermentation time
3. Greater yields
4. Greater fermentation sugar conc.
 After sterilisation the fermenter is gassed with CO2, before and
after inoculation fermenter contents are stirred with CO2.
 Fermentation medium mainly consists of molasses and corn
steep liquor.
 Fermentation is commenced at 34˚C at pH 5.8 to 6 for 36
hours.

10.  The 36 hours fermentation
has 3 phases:
1. During first 18 hours, the
pH value decrease to 5.2
due to formation of acetic
acid and butyric acid.
2. During next 18 hours, the
pH value increase due to
conversion of above
acids in to acetone and
butanol.
3. In the last stage growth
and solvent production
stop, pH value remain
constant at pH 5.8. the
products can be
recovered now.

12.  Contamination due to bacterio-phages and Lactobacilli is a
common problems, make absolute sterility mandatory.
 Above table shows yields of 90 m3 fermenter with 5.85
tons of fermentable sugar.
 CO2 produced in fermentation is recovered and converted
to liquid CO2 or dry ice.
 Acetone, butanol and ethanol are recovered through
continuous distillation and fractionation.
 The residue left after the distillation are dried and used as
an animal feed.

13. Uses:
 Butanol is a valuable solvent for the
production of lacquer(used to prepare the
finish of automobiles), latex, enamels….
 Used as biofuel (it has similar physical
properties to gasoline).
 Used as an additive to plastics to keep
them flexible.
 Used as a solvent in the manufacture of
antibiotics , vitamins , and hormones.
 Acetone is important in making cordite.