BIODEGRADATION OF

STARCH

VIPIN MOHAN

2011-09-112

College of Agriculture

Vellayani, TVM

Biodegradation is the chemical

dissolution of organic materials by

biological means (mainly by

microorganisms).It is nature’s way of

recycling waste or breaking down

organic matter into nutrients that can

be utilised by other organisms.

Organic materials can be degraded

Aerobically use oxygen

Produce carbon dioxide & water

Anaerobically Absence of oxygen

Use chemicals as electron acceptor like nitrate

sulphate & iorn

STARCHStarch or amylum is a carbohydrate

consisting of a large number of glucose

units joined by glycosidic bonds.

Carbohydrate reserve in plants.

Starch consists of a mixture of two types of

polymers: amylose and amylopectin.

AMYLOSE

Amylose-linear polysaccharide-linked by α-(14)

glycosidic linkage between glucose residues.

Water soluble

AMYLOPECTIN

Amylopectin is branched linked by α(16) linkage b/w

glucose residues and also by α-(14).

Water insoluble.

CHEMICAL STRUCTURE OF STARCH

TYPES OF STARCH

Potato Starch

Corn Starch

Maize Starch

Rice Starch

Tapioca Starch

Wheat Starch

Soya bean Starch etc…

The classic test for the presence of starch is reaction with iodine.

If starch molecules are present in a substance, the addition of iodine yields a

deep blue color.

AMYLASE

Starch molecules are broken down by enzyme known as

amylase.

Bacteria and fungi secrete amylases for extracellular

digestion. When they have broken down the insoluble

starch, the soluble end products such as (glucose or

maltose) are absorbed into their cells.

Many microorganisms produce this enzyme, the most

commonly used in industrial production are

bacillus subtilis, bacillus licheniformis,

bacillus amyloliquifaciens and aspergillus niger.

BACTERIA FUNGI

Bacillus amyloliquefacicns AspergillusB. caldolyticus CandidaB. coagulans CephalosporiumB. cereus MucorB. lichenformii NeurosporaB. subtilis PenicilliumB. stearothermophilusEscherichia spp.. Lactobacillus spp.. Micrococcus spp. Pseudomonas spp. Proteus spp. Serratia spp.

Bacteria and Fungi producing AMYLASE

Bacillus amyloliquefacicns Bacillus coagulans Aspergillus

Penicillium NeurosporaMucor

BIODEGRADATION BY MICROORGANISMS Microorganisms have high surface area to volume ratio,

this allows extensive interaction with the environment

and their high metabolic rate.

Microbial enzymes are less choosy and generally exibit

broader substrate specificity.

Eventhough individual microbial cell can only metabolise

a limited number of substrates they can be cultured

as a large biomass.

Microorganisms can metabolize all naturally

occuring compounds and many xenobiotic

compounds.

Relative ease of passage genetic material into

microorganism(recombinant microorganisms to increase

efficency) compared to cells of higher organisms.

Allow for quick adaptation through the acquisition

of new metabolic capabilities

Microbial amylases usually contain three type

of amylases. 1.α-AMYLASE (ALPHA-AMYLASE)

Produced by bacteria and fungi, Industrially it is obtained from Bacillus amyloliquefaciens.

Ca-metalloenzyme

By acting at random location along the starch chain ,a-amylase breaks down long chain carbohydrate ultimately yielding maltotriose and maltose or glucose and limit dextrin from amylopectin.

Because it can act anywhere on the substrate a-amylase tends to be faster than β -amylases.

It is called an endoglucanase because it normally attacks internal

α -1,4 bonds.

2.β-AMYLASE

Found primarily in plants, but is infrequently made by bacteria.

Removes maltose molecules from the non reducing ends of starch.

β-amylase catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time.

So it removes molecules from the external end, it is called an exoglucanase.works from the non reducing end.

Fruit ripening starch converted to maltose by β -amylase which gives sweet flavor.

Found mainly in plants but is infrequenly made by bacteria.

3.γ-AMYLASE ( GLUCOAMYLASE OR AMYLOGLUCOSIDASE)

γ-Amylase will cleave α(1-6) glycosidic linkages, as well as

the last α(1-4 )glycosidic linkages at the non reducing end

of amylose and amylopectin, yieldin glucose.

Unlike the other forms of amylase, γ-amylase is most efficient in

acidic environments and has an optimum pH of 3.

Inverting exo acting starch hydrolases releasing β-glucose from non

reducing end of starch.

It is derived by submerged fermentation of specially selected

producer strains of Aspergillusniger.

Selectively attacks the last bond on the reducing terminal.

PULLULANASE OR ISOAMYLASE

A special kind of glucanase, an amylolytic enzyme that degrades

pullulan.

Pullulan is a polysaccharide polymer consisting of maltotriose units.

Three glucose in maltotriose connected by α(1-4) glycosidic bond

whereas consecutive maltotriose units are connected to each other by

α(1-6) glycosidic bonds.

Pullulan is produced from starch by fungus Auerobasidiumpullulans.

TWO MAIN PROCESS IN DEGRADATION OF STARCH

The initial step in random degradation is the splitting of large chains

into various smaller sized segments.

This drastically reduces the viscosity of gelatinized starch solution,

resulting in Liquefaction - thinning of the solution.

The final stages of degradation are mainly the formation of mono-,

di-, and tri-saccharides – called as Saccharification , due to the

formation of saccharides.

Eg : Bacterial alpha-amylase - randomly attacks only the alpha-1,4

bonds- belongs to the liquefying category.

The fungal alpha-amylase belongs to the saccharifying category.

FACTORS AFFECTNG BIODEGRADATION

Light, Water and O2(if aerobic)

Environmental factor(physical and chemical)

Temperature (Thermophiles, Mesophils)

Nutritional factor

METHODS OF MEASURING BIODEGRADATION

Respiratory test for aerobic microbes

Solid waste sample + microorganism + soil in a container

and aerate the mixture . Over the course of time

Microorganisms digest the sample bit by bit and produce

CO2. Resulting amount of CO2 serves as an indicator of

degradation.

Applications of STARCH

degradation

FOOD INDUSTRY

High fructose corn syrup(HFCS)

Source Corn starch

Enzymes alpha-amylase, glucoamylase, glucose-isomerase

PRODUCTION IN HIGH FRUCTOSE CORN SYRUP

Beer production(BREWING)

Source – cereals (Barley)

Enzymes – Alpha amylase,Beta amylase,Amyloglucosidase.

The lowest temperature

(45 ºC) is the optimal

temperature for cell

wall degrading

enzymes, β-glucanases.

The proteases works

best at 52 ºC, the β-

amylase best at 63 ºC

and the α-amylase at

72°C. The last step in

the mashing is

inactivation of the

enzymes at 78 ºC.

TEXTILE INDUSTRY

DESIZING

Desizing is the process of removing the size material from

the warp yarns in woven fabrics.

Natural desizing agent – Starch and starch derivatives(Used for

giving strength to the yarns during weaving).

Biodesizing-Complete removal of starch-containing cloth

without fiber damage is done by using enzymatic desizing

agents like liquid bacterial amylase.

The enzymatic desizing process can be divided into

three stages.

1. Impregnation

2.Incubation

3.After wash

Impregnation

Enzyme solution is absorbed by the fabric.

During this stage gelatinization of the size

(starch) is to the highest possible extent.

Incubation:

The enzyme breaks down the size. Long

incubation time allows a low enzyme

concentration.

After-wash:

The breakdown products from the size are

removed from the fabric. This is best obtained by

a subsequent detergent wash (with NaOH) at the

highest possible temperature.

FUEL PRODUCTION

Starch-based ethanol

(Bioethanol) Source Corn starch

Enzymes Alpha amylase,glucoamylase

5 steps in bioethanol production

Grinding

Cooking

Fermentation

Distillation

Dehydration

Detergent industry

Acts on stains containing starch by degrading starch to

short-chain sugars. Typical stains are sauces, gravy and

ice-creams.

Also used in automatic dishwashing to degrade the

residues of starchy foods such as potatoes, gravies,

custard, chocolate, etc.

Oxidative stability of amylases is one of the most

important criteria for their use in detergents.

Examples of amylases used in the detergent industry are

derived from Bacillus or Aspergillus .

.

USE OF STARCH IN BIO-DEGRADABLE PLASTICS

Paper industry

Used as a sizing agent

The largest proportion of starch is added to the

surface of paper in coating formulations.

starch products also are based on a renewable

resource.

Paper uses for cups, bags, cartons, and various

printing applications can require that it resist

water absorption and penetration.

Increasing biodegradability, strength, writing

quality, erasability,

MEDICAL AND PHARMACUETICAL INDUSTRY

Used for Serum evaluation.

Used as biosensors with an electrolyte

isolator semiconductor capacitor (EIS-CAP)

transducer for process monitoring.

Alpha-amylase has been used to prepare a

hybrid membrane using chitosan as a

dispersant in the sol-gel process.

Can be also used as an enzyme thermistor

for the biochemical analysis of

cyclodextrins.

Starch conversion Bacillus amyloliquefaciens , Bacillus

stearothermophilus or Bacillus

licheniformis .

Detergent industry Bacillus or Aspergillus.

Fuel alcohol production Saccharomyces fibuligera, Bacillus

subtilis.

Food industry Bacillus stearothermophilus.

Textile industry Bacillus strain.

Paper industry Bacillus strain.

Industrial Purpose Microbes producing

STARCH BASED BIO-PRODUCTS !!!

BENEFITS

Cost effective

Reduce operating expenses

Environmentally safe

No adverse effects

Great public relations aspect(green

solution)