CHAPTER 6:

BIOCONVERSION

TECHNOLOGIES

Course Outcome

Ability to discuss the technologies available in

bioconversion.

Introduction: BIOCONVERSION

ABUNDANCE OF BIOMASS

WHOLE OVER THE

WORLD

Sugarcane

residue

Impose environmental

problems

What is Biomass

Living and dead biological material that can be

used for biofuel or industrial production.

Focus on biomass produced from agriculture

activities.

How to use the biomass?

1. Convert to useful products.

2. 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).

Physical Method

Mechanical processes; pelletization of wood waste,

paddy straw.

Extraction process

Thermo chemical methods

A process where heat is the dominant mechanism to

convert biomass into another chemical form

Three different classes of thermo chemical:

1. Combustion/burning

2. Gasification – convert carbonaceous materials into

carbon monoxide&hydrogen (syngas)

3. Liquefaction

Biological methods 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:

1. Lactic acid bacteria

2. Acetic acid bacteria

3. Bacteria of alkaline fermentation

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.

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.

\

Types of Bioconversion

Solid state fermentation process can be

defined as the growth of microorganisms

especially fungus on insoluble substrate

with sufficient moisture but not free water.

On the contrary, in liquid state

fermentation, microorganisms are grown in

liquid media with existence of water.

Types, Advantages & Disadvantages

of Bioconversion

Factor Solid-state fermentation Liquid state fermentation

Substrates Polymer insoluble substrates: starch, cellulose, pectin,

lignin. Substrate requires pretreatment (size reduction

by grinding, chopping, homogenization etc)

Soluble substrates do not require pretreatment.

Aseptic conditions Vapor treatment, non-sterile conditions Heat sterilization and aseptic control

Water Limited consumption of water, no effluent High volumes of water consumed and effluent

discarded

Metabolic heating Low heat transfer capacity Easy control of temperature

Aeration Easy aeration and high surface exchange air or

substrate

Limitation of soluble oxygen, high level of air

required

pH control Buffered solid substrates Easy pH control

Mechanical agitation Agitation is difficult, therefore static conditions

preferred

Good homogenization

Scale up Need for engineering and new design equipment Industrial equipments available

Inoculation Spore inoculation, batch, high inoculum volume

needed, spore have longer lag time due to the need

for germination

Easy inoculation, continuous process

Contamination Risk of contamination for low rate growth fungi Risks of contamination for single strain bacteria

Energetic consideration Low energy consuming High energy consuming

Volume of equipment Low volumes and low cost of equipments High volumes and high cost technology

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

Acetic acid production

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

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.

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

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

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.

Factor influence citric acid production using submerged culture method.

sensitive to iron. Medium used must be iron-deficient. 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 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.

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 ethanol + carbon dioxide

C6H12O6 + yeast 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

27/11/2012

Sugar containing biomass : sugar cane, molasses, sugar beet

Production steps :

1. milling/grinding (extract juices)

2. fermentation of juices (sugar)

with yeast sugar + yeast ethanol + carbon dioxide

C6H12O6 + yeast 2C2H5OH + 2CO2

3. Distillation

4. Dehydration

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.

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 ethanol + carbon dioxide

C6H12O6 + yeast 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

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.

3. Hydrolysis of cellulose with enzyme nto produce sugar

4. Fermentation of sugar with yeast

sugar + yeast ethanol + carbon dioxide

C6H12O6 + yeast 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

Biodiesel refers to a vegetable oil- or animal fat-based 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.

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

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

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

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

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. 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

2. Rural agricultural residues and damaged crops could have a higher value as soil amendments and biomass feedstock