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What is bioconversion
•
Bioconversion is the conversion of organic
materials, such as plant or animal waste, into
usable products or energy sources by
biological processes or agents, such as certain
microorganisms or enzymes.(wikipedia
dictionary).
• Things to consider:
1. What to convert.
2. what to use
3. What to get
What bioconversion can do
• Bioconversion can be carried out physically,
thermochemically and biologically.
• This process has been applied in the production
of foodstuffs, organic chemicals and energy.
• Biological methods for bioconversion has given
priority with the use of microorganisms as less
expensive yet effective agents.
• This process is also known as fermentation.
Importance group of bacteria in
bioconversion
1. Lactic acid bacteria
2. Acetic acid bacteria
3. Bacteria of alkaline fermentation
http://bioconversion.blogspot.com/
Conversions by Acetic Acid bacteria
• A second group of bacteria of importance in food fermentations are
the acetic acid producers from the Acetobacter species. Acetobacter
are important in the production of vinegar (acetic acid) from fruit
juices and alcohols. The same reaction also occurs in wines, oxygen
permitting, where the acetobacter can cause undesirable changes –
the oxidation of alcohol to acetic acid.
• The vinegar process is essentially a two stage process, where
yeasts convert sugars into alcohol, followed by acetobacter, which
oxidise alcohol to acetic acid.
• Acetic acid fermentation
• Acetobacter convert alcohol to acetic acid in the presence of excess
oxygen.
• The oxidation of one mole of ethanol yields one mole each of acetic
acid and water;
• C2H5OH
CH3CHO +H2O  CH2CH(OH)2 CH3COOH + H2O
ethanol
acetaldehyde
hydrated acetaldehyde acetic acid
1.Usage - Acetic acid is a chemical reagent for the
production of chemical compounds. The largest
single use of acetic acid is in the production of
vinyl acetate monomer, closely followed by
acetic anhydride and ester production. The
volume of acetic acid used in vinegar is
comparatively small.
2. Type of culture – highly aerated submerged
processes.
2. Raw material-diluted purified ethanol from grape
juice, apple juice, barley malt etc.
3. Factors influence-Oxygen supply and the
concentration gradients of ethanol and acetate.
1. Lack of oxygen
• lack of O2 will killed the bacteria because they are
extremely sensitive.
• to overcome this problem, has to use efficient aeration
• efficient aeration can be achieved with the used of
compressed air and proper mechanical device.
• for efficient aeration also have to consider shear stress
imparted by the fluid and the microorganisms itself.
• the efficiency depends on the ratio between the energy
input necessary per unit weight of O2 transferred to the
culture.
2. Over-oxidation
• when there is over-oxidation, acetic acid will convert to
CO2 and H2O.
• will decrease acetic acid production.
• have to maintain acetic acid concentrations above 6% of
the total culture.
• and avoid the total depletion of ethanol.
Citric Acid Production
1. Usage- has long been used in soft drinks manufacture
as an acidulant, as an aid to jam setting and as a
general additive in the confectionery industry.
2. Bacteria used – Aspergillus niger or Candida yeast
3. Culture method – Surface culture method was used
using A. niger and submerged method using Candida
yeast.
4. Raw material; Molasses
5. Factor influence using surface culture method.
•
sensitive to Mn2+ concentration. Production reduced
at Mn2+ low as 3 mg/L
•
Oxygen supply
•
pH should maintain below 2.0. At higher values,
A.niger accumulates gluconic acid rather than citrate.
5. Biochemistry of production
- Involves few steps
a. Breakdown of hexoses to pyruvate and
acetyl CoA.
b. The anaplerotic formation of
oxaloacetate from pyruvate and CO2
c. The accumulation of citrate within the
tricarboxylic acid cycle
- The key enzyme is pyruvate carboxylase,
constitutively produced in Aspergillus
species.
Advantages of bioconversion
• While focusing much of their attention on
building advanced E-Flex technology to
reduce the need for liquid fuels, GM
certainly recognizes that ethanol is going
to be a major form of renewable fuel
globally during most of the coming century.
Convert solar energy into liquid fuels
Reduce Greenhouse Gases
Please read article entitle “Carbon’s New Math” to get full picture on this
Advantages.
Remediate ecological disaster
1. forest density that is 4 to 10 times historic norms
– creates conditions that exacerbate droughts
leading to forest fires and bug infestations
2. municipal solid wastes – is getting out of
control necessitating bigger landfills that are
further away from our urban centers. This
excess waste contributes to land, water, and air
pollution
3. Rural agricultural residues and damaged
crops could have a higher value as soil
amendments and biomass feedstock
Bioconversion technology for
biofuel production
• Two methods are available;
1. The fermentation of biomass for biogas
2. The fermentation of biomass for ethanol
The production of biogas (methane)
- Can be achieved in three steps:
i. Acid production (hydrolysis)
ii. Acid reduction
iii. Methane production
Bioconversion technology for
ethanol production
• It is similar to the technology of manufacturing
drinkable alcohol.
• In many countries, alcohol has been used in
engine in a mixture of petrol and alcohol (1020%).
• The largest program PROALCOL in Brazil, the
ethanol was mixed with petrol in the ratio 80:20.
• Cannot use pure ethanol since has low calorific
value, 40% lower than petrol.
Basic biology and technological method
- biologically, alcohol was formed when there is an action
of microorganisms
in the form of yeast anearobs on sugar containing solution.
sugar + yeast
C6H12O6
ethanol
+
yeast
+
carbon dioxide
2C2H5OH + 2CO2
- For commercialization of ethanol production, two different
types of substrates
are available for fermentation.
- Both substrates need different type of pre-treatment.
1. Sugar containing biomass
2. Starch containing biomass
- Starch (C6H10O5), is first of all converted into glucose.
• Starch (C6H10O5), is first of all converted
into glucose.
+ H2O
- Example of sugar containing raw products
are sugarcane, sugarbeet, sugar millet and
fodder beet.
- Example of sugar containing starch are
maize, grain, cassava and potato.
- Technologically, there are differences in
fermentation process of sugar or starch
containing raw materials.
- For sugar containing plants, the juice of sugar is
extracted and processed into sugar.
- For starch containing plants, the starch is first
extracted and mixed with warm water.
- This resulting in the formation of paste like
substances.
- The paste is then converted into glucose in
dexternisation saccharination process.
- The glucose then will be disintegrate in the
disintegration process.
- Glucose from both process then fermented in
the fermenter and ethanol finally obtained
through the process of distillation.