Environmental Biotechnology Concepts
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Questions and Answers

What are two major activities that cause contamination of soils and groundwater by toxic compounds?

Industrial and agricultural activities

What is the process called that uses living organisms to eliminate organic or mineral pollutants present in natural environments?

Bioremediation

Which of the following is NOT a type of bioremediation technique?

  • Land farming
  • Electrolysis (correct)
  • Biostimulation
  • Composting
  • Bioventing
  • Biosparging

    • What are the two main types of bioremediation techniques?

    <p>In situ and ex situ</p> Signup and view all the answers

    Bioventing employs high air flow rates to speed up the biodegradation process.

    <p>False (B)</p> Signup and view all the answers

    What does biosparging involve?

    <p>Involves the injection of air under pressure below the water table to increase groundwater oxygen concentrations and enhance biodegradation by naturally occurring bacteria.</p> Signup and view all the answers

    What does biostimulation involve?

    <p>Involves supplying oxygen and nutrients by circulating aqueous solutions through contaminated soils to stimulate naturally occurring bacteria to degrade organic contaminants.</p> Signup and view all the answers

    What does bioaugmentation involve?

    <p>Involves the addition of microorganisms indigenous or exogenous to the contaminated sites.</p> Signup and view all the answers

    What does landfarming involve?

    <p>Involves spreading contaminated soil over a prepared bed and periodically tilling it to stimulate indigenous microorganisms and facilitate their aerobic degradation of contaminants.</p> Signup and view all the answers

    Composting is often used for the treatment of heavy metal contamination.

    <p>False (B)</p> Signup and view all the answers

    Describe the difference between landfarming and composting.

    <p>Landfarming involves spreading contaminated soil over a prepared bed and periodically tilling it, while composting involves combining contaminated soil with nonhazardous organic materials.</p> Signup and view all the answers

    What are biopiles?

    <p>Biopiles are a hybrid of landfarming and composting, creating aerated composted piles for treating surface contamination.</p> Signup and view all the answers

    What are bioreactors?

    <p>Bioreactors are vessels or apparatuses designed to create a controlled environment for processing contaminated solid material or water, enhancing bioremediation.</p> Signup and view all the answers

    Slurry reactors involve the use of a mixture of solid particles suspended in a liquid, typically water.

    <p>True (A)</p> Signup and view all the answers

    What is phytoremediation?

    <p>Phytoremediation is the use of plants to decontaminate soil and water by extracting heavy metals or contaminants.</p> Signup and view all the answers

    Which of the following is NOT a type of phytoremediation?

    <p>Phytosorption (E)</p> Signup and view all the answers

    Describe the process of phytoextraction.

    <p>Plants known as hyperaccumulators absorb contaminants through their roots and concentrate them in their stems, leaves, or other tissues.</p> Signup and view all the answers

    What does phytotransformation involve?

    <p>Involves the uptake of organic contaminants from soil, sediments, or water and their subsequent transformation into more stable, less toxic, or less mobile forms.</p> Signup and view all the answers

    What does phytostabilization involve?

    <p>Involves the reduction of the mobility and migration of contaminated soil by plants or roots.</p> Signup and view all the answers

    What does phytodegradation involve?

    <p>Involves the breakdown of contaminants through the activity of proteins and enzymes produced by plants or soil organisms.</p> Signup and view all the answers

    What does rhizofiltration involve?

    <p>Involves the uptake of contaminants by plant roots, often used to reduce contamination in natural wetlands and estuary areas.</p> Signup and view all the answers

    What is biolixiviation?

    <p>The ability of certain bacteria to extract metallic elements from minerals by solubilizing them.</p> Signup and view all the answers

    What does biosorption involve?

    <p>Involves the binding and concentration of metal ions by living, inactive, or dead biomass.</p> Signup and view all the answers

    What is the difference between passive and active biosorption?

    <p>Passive biosorption involves the binding of metal ions at the surface of the cell membrane, while active biosorption depends on cellular metabolism.</p> Signup and view all the answers

    What is precipitation in the context of bioremediation?

    <p>The process of forming insoluble metal compounds, often through the actions of sulfate-reducing bacteria.</p> Signup and view all the answers

    Which of the following factors can influence the rate of biodegradation?

    <p>All of the above (F)</p> Signup and view all the answers

    What is a recalcitrant compound?

    <p>A compound that is very slow or impossible to biodegrade using biological processes.</p> Signup and view all the answers

    Natural compounds can never be recalcitrant.

    <p>False (B)</p> Signup and view all the answers

    The half-life of a pollutant refers to the time it takes for 90% of the pollutant to degrade.

    <p>False (B)</p> Signup and view all the answers

    What are the three main categories of microbial depollution mechanisms?

    <p>Degradation, mineralization, and cometabolism.</p> Signup and view all the answers

    Explain the concept of cometabolism.

    <p>Cometabolism is the unexpected conversion of a compound due to low enzyme specificity, often involving the degradation of a xenobiotic as a side effect of another metabolic pathway.</p> Signup and view all the answers

    Detoxifying transformations always result in the complete breakdown of a pollutant.

    <p>False (B)</p> Signup and view all the answers

    What is the primary function of oxygenases in the biodegradation of aromatic compounds?

    <p>Oxygenases catalyze the incorporation of oxygen atoms into the aromatic ring, leading to the formation of catechol.</p> Signup and view all the answers

    Both ortho and meta cleavage pathways can occur within the same organism.

    <p>True (A)</p> Signup and view all the answers

    What are the main factors affecting the degradation of PAHs?

    <p>The number of rings, the number and position of substituents on the ring, and the degree of saturation of the rings.</p> Signup and view all the answers

    Explain how the addition of substituents affects the biodegradation rate of benzene.

    <p>Adding substituents to benzene can significantly affect its biodegradation rate, with some substituents increasing persistence and others having less of an impact.</p> Signup and view all the answers

    What is the primary mechanism of DDT degradation?

    <p>Reductive dechlorination reaction primarily by bacteria in soil and water.</p> Signup and view all the answers

    Organochlorine insecticides are generally more persistent than organophosphate insecticides.

    <p>True (A)</p> Signup and view all the answers

    What are the main groups of microorganisms capable of degrading hydrocarbons?

    <p>Bacteria, yeasts, and filamentous fungi.</p> Signup and view all the answers

    What are the major factors affecting the degradation of hydrocarbons?

    <p>Temperature, oxygen availability, nutrient availability, pH, and water saturation.</p> Signup and view all the answers

    In aquatic environments, hydrocarbons tend to sink to the bottom due to their density.

    <p>False (B)</p> Signup and view all the answers

    Hydroperoxidation is an anaerobic process.

    <p>False (B)</p> Signup and view all the answers

    Dehydrogenation reactions require molecular oxygen.

    <p>False (B)</p> Signup and view all the answers

    Explain the concept of subterminal oxidation in the context of hydrocarbon degradation.

    <p>Subterminal oxidation involves the breaking of carbon-carbon bonds within a hydrocarbon chain at a subterminal site, leading to the formation of shorter chain hydrocarbons.</p> Signup and view all the answers

    The biodegradation of aromatic compounds usually involves the initial formation of catechol.

    <p>True (A)</p> Signup and view all the answers

    What are the two main types of oxygenases involved in aromatic degradation?

    <p>Monooxygenases and dioxygenases.</p> Signup and view all the answers

    The addition of a single substituent to benzene always increases its biodegradation rate.

    <p>False (B)</p> Signup and view all the answers

    What are the two main pathways for the cleavage of catechol during aromatic degradation?

    <p>Ortho cleavage and meta cleavage.</p> Signup and view all the answers

    Explain the general mechanism of dehalogenation.

    <p>Dehalogenation involves the removal of halogen atoms (such as chlorine or bromine) from a molecule, usually through a substitution or elimination reaction.</p> Signup and view all the answers

    Dehalogenation can occur without breaking the aromatic ring.

    <p>True (A)</p> Signup and view all the answers

    Which of the following is a major source of PAHs in the environment?

    <p>All of the above (D)</p> Signup and view all the answers

    Study Notes

    • Environmental Biotechnology
    • Bioremediation encompasses concepts like in situ and ex situ bioremediation, biodegradation of pollutants, bioleaching, biosorption, and the accumulation of heavy metals.
    • Pollution is the introduction of harmful substances or energy into an environment. Industrial and agricultural activities contribute to this.
    • Bioremediation utilizes microorganisms to eliminate organic or mineral pollutants in natural environments.
    • Terminology
    • Depollution involves the elimination or inactivation of pollutants, via physical, chemical, or biological methods.
    • Biodegradation is the partial or complete breakdown of a substance by biological agents.
    • Biotransformation refers to the alteration of a substance by biological agents, including incomplete metabolism.
    • Biostimulation is the stimulation of indigenous microorganisms by adding nutrients and controlling environmental factors.
    • Bioaugmentation introduces selected microorganisms to help indigenous microbes break down pollutants.
    • Bioreduction is the reduction of oxidized compounds using biological methods.
    • Bioleaching is the extraction of metals from sludge, soil, sediments, or mineral by microbes inducing solubilization.
    • Biofixation/biosorption is the retention of pollutants, mainly metals, onto microorganisms present in a liquid effluent.
    • Xenobiotics are synthetic compounds created by humans, not found in nature.
    • Phytoremediation utilises plants (vascular plants, algae, or fungi) to eliminate or control contaminants or accelerate the degradation of compounds using microbial activity.
    • Phytotransformation involves plants taking up contaminants and transforming them.
    • Phytostabilization uses plants or roots to keep contaminants in place and reduce their mobility.
    • Phytoextraction is the capacity of plants to accumulate contaminants in their parts (leaves, stems, etc.).
    • Bioremediation
    • Bioremediation is a technology that uses living organisms (bacteria or fungi) to clean up pollutants in soil and water. It's usually done in situ.
    • It is potentially more cost-effective than conventional techniques.
    • Thorough understanding of how microorganisms transform compounds, survive in polluted environments, and how to effectively apply it in contaminated sites is necessary for successful bioremediation.
    • Bioremediation requires a thorough understanding of the specific microorganisms involved and the environmental conditions for optimal effectiveness.
    • Needs of bioremediation
    • Microorganisms require specific conditions for effective bioremediation.
    • Source of energy, electron acceptor, moisture, pH, temperature, absence of toxicity, and elimination of metabolites in the correct amounts are essential.
    • Pollutant Types
    • Metals are essential for life at very small amounts (trace elements), like sodium, potassium, manganese, and calcium. They're part of the metabolism.
    • Heavy metals (cadmium, mercury, aluminium, and lead) are usually present in trace amounts in the environment.
    • Organic compounds include: Petroleum hydrocarbons (like diesel, gasoline, kerosene), wastes from oil exploitation, sludge from oil operations, organic residues from chemical industries (alcohols/acids), and halogenated compounds (herbicides, pesticides, fungicides).
    • Bioremediation Techniques
    • In situ bioremediation techniques include bioventing (supplying air and nutrients to contaminated soil), land farming (excavating and spreading contaminated soil), biosparging (injecting air under pressure to groundwater), composting (adding non-hazardous organic materials to contaminated soil), biostimulation (stimulating indigenous microorganisms), biopiles (aerated composted piles), and bioreactors (processing contaminated material).
    • Ex situ bioremediation techniques mostly involve the use of bioreactors.
    • Bioventing
    • Bioventing is a common in situ technique to supply air and nutrients to contaminated soil using wells and low air flow rates for biodegradation.
    • It minimizes contaminant volatilization to the atmosphere. It's used with shallow contamination.
    • Biosparging
    • This in situ technique involves injecting air under pressure to increase groundwater oxygen and enhance rate of biological degradation.
    • Increases mixing, and so contact, between soil and groundwater.
    • Low cost of installing small diameter injection points.
    • Biostimulation
    • This method involves supplying oxygen and nutrients using aqueous solutions through contaminated soil to stimulate naturally occurring bacteria.
    • It's suitable for both soil and groundwater.
    • It typically includes methods such as infiltration of water containing nutrients and oxygen.
    • Bioaugmentation
    • For bioremediation, use of added indigenous or exogenous microorganisms, is beneficial at contaminated sites.
    • Added microbial cultures (non-indigenous) rarely compete effectively with the indigenous population to sustain active levels in some cases.
    • Indigenous microorganisms effectively degrade waste when land treatment units are well managed.
    • Land Farming
    • This simple technique involves excavating and spreading contaminated soil to stimulate indigenous microbes for aerobic biodegradation over a surface area.
    • The excavated soil is tilled periodically till pollutants are degraded. It's mainly used for shallow contaminants.
    • Composting
    • Combines contaminated soil with non-hazardous organic materials like manure to promote microbial growth and elevated temperatures. This supports microbial populations for degradation
    • The presence of these materials improves the microbial community.
    • Biopiles
    • Hybrid of landfarming and composting, with engineered cells that are aerated composted piles.
    • Typically used to treat surface contamination from petroleum hydrocarbons. It controls contaminants by minimising leaching and volatilization.
    • Creates an environment for indigenous aerobic and anaerobic microorganisms.
    • Bioreactors
    • Bioremediation in reactors involves the processing of contaminated materials within controlled systems (soil, sediment, and sludge).
    • Slurry reactors create a three-phase mixing system that increases bioremediation and is designed to process soil-bound and water-soluble contaminants. This involves mixing microorganisms within water slurries of contaminated soil.
    • Phytoremediation
    • Plants are beneficial in bioremediation, and this method is called Phytoremediation.
    • Use of plants to eliminate or control contaminants in soil or water by extraction of heavy metals or pollutants.
    • Plants grown in polluted soil are specialized for this.
    • Plants extract contaminants via root uptake or breaking down in the soil, then storing the contaminants in their plant structures and biomass.
    • Harvested and removed from the site.
    • Cost effective, and usually environmentally friendly.
    • Phytoextraction
    • Certain plants (hyperaccumulators) take up contaminants through roots, concentrating them in stems, leaves, or tissues.
    • Harvested plants and pollutants are removed along with plant biomass.
    • Effective for metals like lead, cadmium, zinc, or arsenic.
    • Phytotransformation
    • The uptake of organic contaminants from soil, sediment, or water is followed by their transformation into more stable and less toxic/mobile forms in plants.
    • This process can reduce the mobility of the contaminant and reduce its toxicity, which can affect the environment significantly
    • Chromium reduction for example.
    • Phytostabilization
    • Plants reduce the contaminants mobility and migration, by adsorbing and binding leachable constituents into the plant structures.
    • Contaminants are contained in a stable plant mass, so they don't re-enter the environment.
    • Phytodegradation
    • This is the breakdown of pollutants in the soil/rhizosphere through enzymes in plants or soil organisms.
    • Rhizodegradation is a symbiosis between plants and microbes, where plants provide nutrients, and microbes improve soil environment.
    • Rhizofiltration
    • This is a water remediation technique where plants' roots absorb pollutants.
    • Useful in natural wetlands and estuary areas for reduced contamination.
    • Limitations of Bioremediation
    • Contaminant type and concentration.
    • Environment type and proximity to groundwater.
    • Soil conditions and nature of organisms involved.
    • Cost-benefit ratio/environmental impact.
    • Applicability to all types of surface contamination.
    • Duration of the bioremediation process.
    • Advantages of Bioremediation
    • Minimal exposure of workers to contaminants.
    • Long-term protection of public health.
    • Cost-effectiveness (cheap).
    • On-site treatment, using minimal space and equipment.
    • Eliminates the need to transport hazardous material.
    • Uses natural processes, transforming pollutants instead of simply moving them.
    • Degradation processes are performed within an acceptable time frame.
    • Disadvantages of Bioremediation
    • Overrun costs.
    • Failure to meet targets.
    • Poor management
    • Climate Issues
    • Potential for release of contaminants into the environment.
    • Difficulty in estimating the treatment time needed.
    • Metal Recovery
    • This process includes techniques like bioleaching and biosorption.
    • Biolixiviation
    • Bacteria extract metallic elements from minerals by solubilizing them.
    • Used for low-grade minerals with metal content less than 40%.
    • Utilizes primarily autotrophic (using CO2) and heterotrophic microorganisms (using organic carbon).
    • Implemented on small and large scales.
    • Biosorption
    • A general term for metal recovery in the presence of biomass.
    • Utilizes biomass from raw products.
    • Sorption process efficiency relates to biomass type and chemistry of the solution.
    • The biosorbent can be modified to enhance sorption capacity.
    • Active Biosorption: (i) Precipitation, (ii) Intracellular accumulation (iii) Oxidation/reduction (iv) Methylation/demethylation.
    • Passive Biosorption (i) complexation (ii) sorption.
    • Main Biosorbents
    • Algae, bacteria, fungi, yeasts, and plants are used for extraction of heavy metals.
    • Biomass can be living, inactive or dead.
    • Methods of extraction include passive (biosorption) and active (bioaccumulation) processes which often occur simultaneously.
    • Mechanisms of Biosorption
    • Biosorption is a complex process where metallic species are deposited on biomass via sorption mechanisms, such as ion exchange, complexation, chelation, and precipitation.
    • Ions attach through physicochemical mechanisms influenced by biomass and environmental conditions.
    • Redox reactions; negatively charged groups (carboxyl, hydroxyl, and phosphate) on biomass absorb metallic cations, via van der Waals and covalent bonds.
    • Electrostatic interactions.
    • Biosorption by Algae
    • Algae have high metal adsorption capacity due to their biopolymers.
    • Diverse types of algae (red, brown, green).
    • Biopolymers include polysaccharides (cellulose, xylan), uronic acids (alginate), and sulfated polysaccharides (agarose, pectin, carrageenan).
    • Some have carboxyl, sulfonic, and hydroxyl groups linked to metal affinity.
    • Biosorption by Fungi and Yeasts
    • Fungi/Yeasts contain chitin (essential component for the cell wall).
    • Some yeasts have high chitin synthase activity.
    • Biosorption with Bacteria
    • Bacteria have reactive surfaces with sorption sites, often with a negative surface charge at neutral pH.
    • Cell wall components include (i) Gram (+): peptidoglycans (ii) Gram (-): outer membranes (hydroxyls, carboxyls, phosphates, amines).
    • Factors influencing Biosorption
    • Physicochemical properties of the medium (pH, temperature, ionic strength, dissolved oxygen concentration, and other ligands).
    • At higher pH, metal hydroxide formation occurs with varying cation reactivity.
    • At lower pH, interaction between metals and organic molecules is favoured.
    • Increased ionic strength reduces the adsorption capacity of bacteria regardless of metal or pH.
    • Metal characteristics (size-charge ratio, ionic radius, valence, speciation, concentration, solubility) influence adsorption.
    • Bio-sorbent characteristics (composition, concentration) influence adsorption.
    • Precipitation
    • Metals can be precipitated as solids: oxides under oxic or sulfides under anoxic conditions.
    • Microbial Sulfate Reduction:
    • A crucial process under anaerobic conditions. Organisms such as Desulfotomaculum and Desulfovibrio are important in this process.
    • Key characteristics include strict anaerobiosis, neutrophilia (optimal pH around 7), and a need for electron donors (like lactate).
    • Hydrogen sulfide production, which reacts with metals, forms insoluble solids, favouring precipitation.
    • Metal precipitation as sulfides depends on the solid's stability, with FeS being more stable than MnS.
    • Applications include groundwater treatment and mine water bioreactor treatment.
    • Intracellular accumulation of metals is followed by transport within the cell.
    • Iron oxidation-reduction reactions convert soluble Fe(II) into less soluble Fe(III), which precipitates as iron oxides. Microbes contribute to Fe(II) phosphate formation.
    • Microbial Sulfate Reduction
    • Precipitation of metals as sulfides is affected by solid stability. FeS is more stable than MnS.
    • Applications include groundwater and mine water treatment.
    • Bioremediation of Gold
    • Gold (Au+) immobilization can be utilized in conjunction with microbial oxidation.
    • Aromatic Hydrocarbon Degradation
    • Benzene, toluene, ethylbenzene and xylenes (BTEX) are examples of aromatic hydrocarbons.
    • Degradation involves two main steps: (1) Hydroxylation and (2) Cleavage of the aromatic ring.
    • Hydroxylation is the addition of a hydroxyl ion (OH) to the aromatic ring, facilitated by monooxygenases or dioxygenases, resulting in catechol formation.
    • Ring cleavage of catechol by specific enzymes leads to complete degradation.
    • Aerobic Degradation of BTEX
    • Hydroxylation of aromatic ring with molecular oxygen and mediated by oxygenases leading to catechol formation.
    • Catechol cleavage progressing to complete degradation.
    • Benzene Degradation
    • Addition of substituents influences biodegradation order.
    • Meta-positioned halogens on phenol show high persistence.
    • Increasing chlorine or bromine increases persistence.
    • Polyaromatic Hydrocarbon (PAH)
    • Multiple associated rings.
    • Resistance to biodegradation.
    • Toxic and carcinogenic.
    • Many compounds (over 70).
    • Found in soils, sediments, and industrial/domestic wastewater.
    • Formed through combustion of fossil fuels, naturally occurring from coal and biological decomposition.
    • Factors Affecting PAH Degradation
    • Number of rings ( >3 is not good), position of substituents on the ring, and degree of ring saturation (unsaturated rings are easier to degrade).
    • Insecticides (DDT Analogues):
    • DDT analogues are products of DDT degradation.
    • Reductive dechlorination during degradation by bacteria in soil and water is crucial.
    • Organophosphates
    • These insecticides are less persistent than organochlorine compounds.
    • Metabolisms by bacteria and fungi (Pseudomonas, Arthrobacter, Streptomyces, and Thiobacillus; Trichoderma).
    • Multiple attack sites and enzymes (phosphatase, mixed-function oxidase, phosphotase, and carboxyl esterase) are required for degradation.
    • Biodegradation Rate of Hydrocarbons
    • Degradation rate varies based on hydrocarbon type, with differences in microbial activity spectra.
    • Specific organisms degrade specific hydrocarbons.

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    This quiz covers key concepts in environmental biotechnology, focusing on bioremediation techniques such as biodegradation and bioaugmentation. It also explores terminology related to pollution and the biological processes used to combat it. Test your knowledge on how microorganisms can help eliminate pollutants and restore environments.

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