Transcript Bioconversion Technologies

ERT 211 BIOCHEMICAL
ENGINEERING
Chapter 6:
Bioconversion
Technologies
Course Outcome

Ability to discuss the technologies
available in bioconversion.
Introduction: BIOCONVERSION
Sugarcane
residue
ABUNDANCE OF BIOMASS
WHOLE OVER THE
WORLD
Impose environmental
problems
What is Biomass
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Living and dead biological material that
can be used for biofuel or industrial
production.
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Focus on biomass produced from
agriculture activities.
How to use the biomass?
1.
2.
Convert to useful products.
Convert to energy.
What method can we use?
 Physically?
 Chemically?
 Biologically?
Energy from biomass
Biofuels
 Bioethanol – made from crops eg sugarcane, corn,
potato, kenaf
 Biodiesel – made from oils/fats using
transesterification process
 Biogas (methane, CO2, N2) – produce by the
biological breakdown of organic matters in the
absence of O2
Products from bioconversion
Industrial chemicals (organic acids, acetic
acids, giberellic acids, biopolymers)
 Food additives (amino acids, nucleosides,
vitamins, fats and oils)
 Health care products (antibiotics, steroid,
vaccines, monoclonal antibodies)
 Industrial enzymes (amylases, proteases,
diastases).
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Physical Method
Mechanical processes; pelletization of
wood waste, paddy straw.
 Extraction process
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Thermo chemical methods
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2.
3.
A process where heat is the dominant
mechanism to convert biomass into another
chemical form
Three different classes of thermo chemical:
Combustion/burning
Gasification – convert carbonaceous materials
into carbon monoxide&hydrogen (syngas)
Liquefaction
Biological methods
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3.
use of the enzymes of bacteria and other
micro-organisms to break down biomass.
micro-organisms are used to perform the
conversion process: anaerobic digestion,
fermentation and composting.
The importance group of bacteria in
bioconversion are:
Lactic acid bacteria
Acetic acid bacteria
Bacteria of alkaline fermentation
What is bioconversion
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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.
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Things to consider:
What to convert
what to use
What to get
1.
2.
3.
What bioconversion can do
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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.
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BIOCONVERSION TECHNOLOGY
FOR
ACETIC ACID PRODUCTION
Acetic acid
CH3COOH, also known as ethanoic acid
 is an organic acid that gives vinegar its sour
taste and pungent smell.
 Acetic acid is one of the simplest carboxylic
acids.
 Usage :
- in vinegar making (4%-18% acetic acid)
- solvent
- cellulose acetate used in photographic film
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Acetic acid production
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Microorganism used : Acetobacter
-
is a genus of acetic acid bacteria
have the ability to convert ethanol to acetic
acid in the presence of oxygen
They are Gram-negative,
aerobic
rod-shaped bacteria.
Type of culture : highly aerated fermentation
 Raw material : diluted purified ethanol from
grape juice, apple juice, barley malt etc.
 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 + O2 → CH3COOH + H2O
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Factors influence acetic acid
production
 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.
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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
Citric acid
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is a weak organic acid C6H8O7
exists in greater than trace amounts in a variety of
fruits and vegetables, most notably citrus fruits
commercial citric acid is produced by fermentation
of carbohydrates or citrus juices
Usage :
- to add an acidic or sour taste to foods and soft
drinks.
- general additive in the confectionery industry.
- pharmaceutical industries
Citric acid production
Microorganism used : Aspergillus niger or
Candida sp. (yeast)
 Culture method : submerged fermentation
system and surface fermentation
 Raw materials : Molasses, sugarcane
syrup, sucrose
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Biochemistry of production (Involves few steps)
a. Breakdown of hexoses (sugar) 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.
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Factor influence citric acid production using
submerged culture method.
 sensitive to iron. Medium used must be irondeficient. Fermentor must be stainless steel to
prevent leaching of iron frm fermentor wall
 Oxygen supply
 pH should maintain below 2.0. At higher values,
A.niger accumulates gluconic acid rather than
citrate.
Ethanol production
Bioconversion technology for
ethanol production
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Ethanol or ethyl alcohol (C2H5OH) is a clear
colourless liquid, it is biodegradable, low in
toxicity and causes little environmental pollution
if spilt.
Ethanol burns to produce carbon dioxide and
water.
Ethanol is widely used in Brazil and in the United
States.
Most cars on the road today in the U.S. can run
on blends of up to 10% ethanol and 90% petrol
Application of ethanol : raw material, solvent,
used in fuel and in chemical, pharmaceutical &
food industries.
Bioethanol, unlike petroleum, is a form of
renewable energy that can be produced
from agricultural feedstocks.
 It can be made from very common crops
such as sugar cane, potato, manioc and
maize.
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Basic biology and technological method
- biologically, alcohol was formed when there is an action of
microorganisms in the form of yeast anaerobs on sugar or
carbon containing solution.
sugar + yeast
C6H12O6 + yeast
ethanol + 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
Bioethanol production
Substrate : Sugar containing
biomass
Sugar containing biomass : sugar cane,
molasses, sugar beet
 Production steps :
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1. milling/grinding (extract juices)
2. fermentation of juices (sugar)
with yeast
sugar + yeast
C6H12O6 + yeast
3. Distillation
4. Dehydration
ethanol + carbon dioxide
2C2H5OH + 2CO2
Bioethanol production
Substrate : Starch containing
biomass
Starch containing biomass : maize, cassava,
grain, potato
 Production steps :
1.Slurry preparation
 The starch-containing substrate
(Cassava powder) is mixed with water
to form slurry.
2.Gelatinization
 The slurry is then gelatinized with
steam (68-74°C). Gelatinization is the formation
of starch paste.
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3.Dextrinization
 Dextrinization is the breakdown of gelatinized starch into
smaller fragments or dextrins by means of α- or Β-amylase.
The action of α-amylase on gelatinized starch results in
dramatic reduction of viscosity.
4.Saccharification
 Saccharification is the complete conversion of dextrins into
glucose (sugar) through the action of glucoamylase.
5.Fermentation
 The resulting sugar is cooled and transferred to a fermentor
where yeast is added. It is catalyzed by the action of
enzymes present in microorganisms like yeasts with ethyl
alcohol as the end product.
sugar + yeast
C6H12O6 + yeast
ethanol + carbon dioxide
2C2H5OH + 2CO2
6.Distillation
 After fermentation, the fermented liquor is transferred to a
distillation process where the ethanol is separated from
the remaining stillage (residue non-fermentable solids and
water). Distillation is the process in which a liquid or vapor
mixture of two or more substances is separated into its
component fractions of desired purity by the application or
removal of heat. This process can usually produce a
95.6% by volume ethanol product.
7.Dehydration
 Ethanol from distillation process is sent to the molecular
sieves column for further dehydration to produce 99.7%
v/v ethanol.
Bioethanol production
Substrate : cellulose
containing biomass
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cellulose containing biomass : paddy straw, wood,
coconut husk, paper waste
Production steps :
1. biomass harvested
2. biomass pretreatment with heat or chemicals (NaOH,
HCL) - Cellulose is a polymer of glucose. Hemicellulose is a copolymer of
different C5 and C6 sugars including e.g. xylose, mannose and glucose, depending
on the type of biomass. Lignin is a branched polymer of aromatic compounds.
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3. Hydrolysis of cellulose with enzyme nto
produce sugar
4. Fermentation of sugar with yeast
sugar + yeast
C6H12O6 + yeast
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ethanol + carbon dioxide
2C2H5OH + 2CO2
5. Distillation
After fermentation, the fermented liquor is
transferred to a distillation process where the
ethanol is separated from the remaining stillage
(residue non-fermentable solids and water).
Biodiesel production
Biodiesel
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Biodiesel refers to a vegetable oil- or animal fatbased diesel fuel consisting of long-chain alkyl
(methyl, propyl or ethyl) esters.
Biodiesel is typically made by chemically reacting
lipids (e.g., vegetable oil, animal fat, soybean,
palm oil, jathropa, sunflower oil, canola) with an
alcohol.
Biodiesel can be used in pure form or may be
blended with petroleum diesel at any
concentration in most injection pump diesel
engines.
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Biodiesel is a light to dark yellow liquid.
It is practically immiscible with water, has a high boiling
point and low vapor pressure.
Biodiesel is a renewable fuel that can be manufactured
from algae, vegetable oils, animal fats or recycled
restaurant greases; it can be produced locally in most
countries.
It is safe, biodegradable and reduces air pollutants, such
as particulates, carbon monoxide and hydrocarbons.
Blends of 20 percent biodiesel with 80 percent petroleum
diesel (B20) can generally be used in unmodified diesel
engines.
Biodiesel can also be used in its pure form (B100), but
may require certain engine modifications to avoid
maintenance and performance problems.
Biodiesel production
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Biodiesel production is the act of
producing the biodiesel, through either
transesterification or alcoholysis. The
process involves reacting vegetable oils or
animal fats catalytically with a short-chain
aliphatic alcohols (typically methanol or
ethanol).
Production steps : biodiesel from soybean seeds
1. Raw materials screening
Remove impurities/dirts from raw materials
2. Oil extraction
Extract oil by pressing or using solvent extraction
3. Purification
Remove impurities from the oil (centrifuge)
4. transesterification
Reaction of oil with methanol+catalyst (NaOH, HCl,
lipase)+heat. Will produce methyl ester and Glycerol
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Transesterification
5. Purification
a) Separation of methyl ester with glycerine.
Glycerine more dense than methyl ester. So
glycerine will settle at the bottom.
b)Wash biodiesel with water to remove contaminants.
Water is heavier than biodiesel and absorb excess
methanol+NaOH
Advantages of bioconversion
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Increase recycling
-generate money from waste
Generation of renewable energy
-bioethanol..biodiesel..biogas
-not too dependent on fossil fuel
Reduce landfill effect
- It saves space in landfills.
Offset to fossil fuel usage
-expand energy freedom of choice.
Reduce carbon emission
-reduce greenhouse gasses by using bioenergy
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Remediate ecological disaster
-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
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.
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
Rural agricultural residues and damaged crops
could have a higher value as soil amendments
and biomass feedstock