Microbiology

“Bioremediation”By

Zoha Arshad

Bioremediation "Remediate" means to solve a problem, and "bio-

remediate" means to use biological organisms to solve an environmental problem such as contaminated soil or groundwater.

The removal of organic wastes by microbes for environmental clean-up is the essence of bioremediation.

Other names used for bioremediation are biotreatment, bioreclamation & biorestoration.

Xenobiotics broadly refer to unnatural, foreign & synthetic chemicals such as pesticide, herbicide & other organic compounds.

Types of Bioremediation

Biostimulation. Bioaugmentation.

Intrinsic bioremediation.

Biostimulation

Biostimulation involves the modification of the environment to stimulate existing bacteria capable of bioremediation. This can be done by addition of various forms of rate limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon (e.g. in the form of molasses).

Bioaugmentation

Bioaugmentation is the practice of adding cultured microorganisms into the subsurface for the purpose of biodegrading specific soil and groundwater contaminants.

Intrinsic Biostimulation

 A type of bioremediation that manages the innate capabilities of naturally occurring microbes to degrade contaminants without taking any engineering steps to enhance the process.

“Bioremediation is a triple corner process”

Redox Clean-up reactions Anaerobic & aerobic metabolism involve

oxidation & reduction reactions for detoxification. Oxygen could be reduced to water & oxidize

organic compounds. Anaerobic reactions can use nitrates.

In return, biomass is gained for bacterial or fungal growth.

In many cases, combined efforts are needed, indigenous microbes found naturally in polluted sites are useful.

Use of Bacteria in Bioremediation

Greatly affected by unstable climatic & environmental factors from moisture to temperature.

E.g. pH in soil is slightly acidic; petroleum hydrocarbon don’t work well <10ºC.

These microbes are usually Thermophilic. Fertilizers are needed. Seeding or bioaugmentation could be useful

too. They contain monooxygenases & dehydrogenases to break down

organic matter including most toxic substances. Oil-eating microbes — with names like Alcanivorax borkumensis —

are some of the smallest living things on earth, but they can have a powerful impact. The bacteria occur naturally in water and, when they come in contact with oil, they eat it, producing the byproducts carbon dioxide and water.

Pseudomonas Genetically engineered bacteria (Pseudomonas) with

plasmid producing enzymes to degrade Octane & many different organic compounds from Crude oil.

List of Genetically engineered Microbes: Pseudomonas putida=Mono & dichloro aromatic

compounds. P.diminuta=Parathion. P.oleovorans=Alkane.

P.cepacia=2,4,5 Trichlorophenol. Acinetobacter Species=4-Chlorobenzene.

Alcaligenes Species=2,4 Dichlorophenoxy acetic acid

Uses of Fungi in Bioremediation

Candida can degrade formaldehyde. Gibeberella can degrade Cyanide. Slurry phase bioremediation is useful too

only for small amounts of contaminated soil.

Composting can be used to degrade household wastes.

White Rot Fungi

It can degrade organic pollutants in soil & effluent & decolorize kraft black liquor e.g. Phanerochaete chrysosporium can produce aromatic mixtures with its lignolytic system.

Pentachlorophenol, Dichlorodiphenyltrichloroethane (e.g. DDT, even TNT (trinitrotoulene) can be degraded by white rot fungi.

Environmental clean up processes

There are two methods of removal & transportation of waste materials;

Insitu Bioremediation. Exsitu Bioremediation.

Insitu Bioremediation

It involves direct approach for the microbial degradation of xenobiotics at the sites of pollution (Soil, ground & water).

It has been successfully applied for clean up Oil spillages, beaches etc.

There are two types of insitu bioremediation. Intrinsic bioremediation.

Engineered bioremediation.

Exsitu Bioremediation

The waste or toxic materials can be collected from the polluted sites & bioremediation with requisite microorganisms can be carried out at Designed places.

Types of Reactions

Aerobic Bioremediation. Anaerobic Bioremediation. Sequential Bioremediation.

Bioremediation of Hydrocarbons Petroleum & its products are Hydrocarbons. Oil constitute a variety

of Hydrocarbons (xylene, Camphor, Octane etc). The pollutants can be degraded by a consortium of microorganisms

e.g. Pseudomonas, Corynebacterium, Mycobacterium, Arthrobacter & Nocardia.

Genetically engineered bacterial strains are used to enhance bioremediation.

In 1979, Anand Mohan Chakarbarty – obtained a strain of Pseudomonas putida that contained XYL & NAH plasmid as well as a hybrid plasmid derived by recombinating parts of CAM & OCT.

In 1990, the USA Govt. allowed him to use this superbug for cleaning up of an oil spill in water of state of Texas.

It was produced on a large scale in laboratory, mixed with straw & dried.

Marine Pollution

Sewage from cities. Industrial effluents. Oil Slick. Pollution from warship. Military activities.

Oil Spill 11 million gallon oil spill from the super

tanker Exxon Valdez Alaska in March 1989.

Straw was spread over oil slicks, the straw soaked up the oil & bacteria broke up the oil into non-polluting & harmless products

Super Bug

Methicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans.

Creation of Super Bug

Phytoremediation It is the use of Plants for accumulation, removal or

conversion of Pollutants. Effective & low cost, environmental friendly. Soil clean-up of heavy metals & organic compounds. Pollutants are absorbed in roots, thus plants removed

could be disposed or burned. Sunflower plants are used to remove Cesium &

strontium from ponds at Chernobyl nuclear power plant. Transgenic plants with exogenous metallothionein (a

metal binding protein) used to remove metals. Approximately 400 plant species have been classified as

Hyperaccumulators of heavy metals such as Grasses, hemp, sunflower, corn, flex, alfalfa, tobacco, willow, Indian mustard, poplar, water hyacinth etc.

Phytoremediation

Phytostabilization Phytovolatilization

Phytostimulation Phytotransformation

Phytoextraction

Bioremediation of Metal contaminated environment

Sources of Heavy Metals

Industries

Agro-Chemicals

WasteDisposal

AtmosphericDeposition

MiningActivities

SourcesOf

HeavyMetals

Biosurfactants These are chemical compounds characterized by

Hydrophobic & Hydrophilic regions in one molecule. Biosurfactants from Bacteria, Cyanobacteria, fungi, yeast

are classified into; Glycolipids.

Lipopeptides. Phospholipids. Glycoproteins.

Polymeric biosurfactants.

Biosurfactant producing GEM

A genetically engineered Pseudomonas aeruginosa.

This new strain can produce a glycolipid emulsifier.

It can reduce the surface tension of oil water interface. The reduced interfacial tension promotes biodegradation of oils.

Bioremediation of industrial waste

A variety of pollutants are discharged in the environment from large no of industries & milks.

Bioremediation of Dyes. Bioremediation of paper or pulp industry.

Prevention & Control of Pollution These activities are supported by a set of legislative and regulatory

promotional measures such as policy statement on abatement of pollution,1992; and the National Environment Policy,2006.

The major action on Abatement on Pollution & Environmental cleanup are as follows: Clean Technology (CT), Control of Pollution (CP), Environment Education (EE), Environmental Impact Assessment (IP), Environmental Information (EI), Environmental Information System (ENVIS), Environment Research (ER), Forest Protection (FPR), Hazardous Substances Management (HSM), Climate Change (CC), Clean Development Mechanism (CDM).

There is an immediate necessity for initiating an ‘All India Coordinated project on bioremediation of the contaminated sites involving perimeter institutions in this field for conducting large scale demonstration projects.

Further departmental agencies & related ministries in India may joint action plan to launch bioremediation from Lab-Pilot-Field scale projects at specific sites.

EnvironmentalCleanup

Joint action of Govt.(various ministries & their department)

Novel Lab level Research

Pilot scale Experiment

Advantages of Bioremediation It is a natural process & therefore perceived by the

public. It is useful for complete destruction of a wide variety of

contaminants. Instead of transferring contaminants from one

environmental medium to another for example, from land to water or air, the complete destruction of target pollutants is possible.

Bioremediation can often be carried out on site, often without causing a major disruption of normal activities.

It can prove less expensive than other technologies that used for cleanup of hazardous wastes.

Disadvantages of Bioremediation

It is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid & complete degradation.

There are some concerns that the products of biodegradation may be more persistent or more toxic than the parent compound.

Biological processes are often highly specific, microbial population, suitable environmental growth conditions, & appropriate levels of nutrients & contaminats.

It is difficult to extrapolate (deduce) from bench & pilot-scale studies to fullscale field operations.

It often takes longer than other treatment options.

Reference

Bioremediation, its application to contaminated sites in India, Ministry of Environment & Forest.

Textbook of Biotechnology-U.sathyanaryana. A textbook of Biotechnology-R.C.Dubey PPT-

Bioremediation methods & its application, MISR university.

http://www.nal.usda.gov/bic/biorem/biorem.htm. http://www.lbl.gov/NABIR/index.html.