L5- Bioremediation Flashcards
What are the organic and inorganic compounds that humans release into the environment?
Environmental contaminants:
POLLUTANTS:
- Naturally occurring compounds in the environment that are present in unnaturally high concentrations
eg. crude oil, refined oil, phosphates, heavy metals
XENOBIOTICS
- Chemically synthesised compounds that have never occurred in nature
eg. pesticides, herbicides and plastics, drugs
What is bioremediation?
BIODEGRADATION
- the use of living organisms such as bacteria, fungi and plants to degrade chemical compounds
BIOREMEDIATION
- a waste management technique that involves the use of organisms to remove or neutralise pollutants from contaminated site
- Isolate microbes that can degrade or eat a particular contaminant
- Requires the control and manipulation of microbial processes in surface reactors or in the subsurface
Types of bioremediation: organisms involved?
BACTERIA BIOREMEDIATION
- Aerobic bacteria- degrade pesticides and hydrocarbons: alkenes and polyaromatics
- Anaerobic bacteria- (not as common) applied to bioremediation of polychlorinateed biphenyls (PCBs) in river sediments and chloroform
- Methanotrophs (methanophiles)- microorganisms that consume methane as their sole source of carbon and energy
MYCOBIOREMEDIATION
- Fungi are able to break down toxins in soils, water and toxic waste. Many species are able to concentrate different metals
PHYTOREMEDIATION
- Treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the contaminant material and dispose of it elsewhere
- Plants remove contaminants by accumulating, degrading or rendering harmless environmental pollutants
Types of bioremediation: where?
IN SITU: “on site”
- most commonly used type of bioremediation because it is the cheapest and most efficient
- Limitation: cannot deal effectively with metal contaminants mixed with organic compound
EX SITU: “off site”
- soil excavation
- relocate in a remote site the polluted materials (energy and fuel oil consumption)
- contaminated land is taken out of the area to be cleaned up by organisms
- usually only used when the site is threatened for some reason eg. oil spill
- Limitation: expensive and damaging to the area since the contaminated land is physically removed
Basic requirements for bioremediation
- Microorganisms
- Energy source
- Electron acceptor
- pH
- Moisture
- Nutrients
- Temperature
- Absence of toxicity
- Removal of metabolites
- Absence of competitive organisms
Mechanism of bioremediation
- Microorganisms destroy organic contaminants in the course of using the chemicals for their own growth and reproduction
- Organic chemicals provide carbon, source of cell building material electrons, source of energy
- Cells catalyse oxidation of organic chemicals (electron donors), causing transfer of electrons from organic chemicals to some electron acceptor
- Electron acceptors:
> In aerobic oxidation, acceptor is oxygen
> In anaerobic, acceptor is (with decreasing efficiency): nitrate, manganese, iron, sulfate
Examples of bioremediation
- Eutrophication
- Soil bioremediation (composting, biopile, bioventing)
- Bacteria used to clean oil spills
Bacteria used to clean up oil spills
- Marine bacteria can assist in cleaning up after oil spills
- Different oils have different properties so an “oil library” can help with selection of the right organisms to clean the spill
- Marine-dwelling bacteria and fungi use hydrocarbons as fuel and emit carbon dioxide as a result
- Break down the ring structure of the hydrocarbons using enzymes and oxygen in the seawater
Limitations:
- Microbes are the only process to break down the oil deeper in the water, far away from physical processes on the surface such as evaporation or waves
- Colder deeper waters inhibit microbial growth
Managing Eutrophication in our rivers and lakes
EUTROPHICATION
Nutrient run off into rivers: Nitrogen and Phosphorus
- Cyanobacterial blooms consistently produce complex toxins in inland waters
- Nitrogen removal from treated sewage using bacteria that deal with nitrogen
Phosphorus Eutrophication management
Phosphate is another potential pollutant that can be released from intensive farming
- In many grain and oilseed animal feeds, phosphate is a component of the plant organic phosphate phytic acid
- phosphate is added to diets to promote better growth
Solution: phytase (microbial digestion enzyme):
- add to animal feeds
e. g. transgenic Enviropig - transgenic plant that produce their own phytase
- genetically engineered heat stable microbial phytase
