Xenobiotics ppt

About Bio degradation of Xenobiotics.

1. BIODEGRADATION OF XENOBIOTICS HYDROCARBONS, PLASTICs & PESTICIDES

2. XENOBIOTICS It is derived from a greek word “ XENOS ”. Xenobiotics are man-made chemicals. They are usually synthesized for industrial or agricultural purposes e.g. pesticides, hydrocarbons, plastics etc. They are also called RECALCITRANTS.

3. biodegradation According to the definition by the International Union of Pure and Applied Chemistry , the term biodegradation is “Breakdown of a substance catalyzed by enzymes. In other words, it is defined as the conversion of toxic chemicals to non-toxic compounds. Biodegradation of xenobiotics can be affected by substrate , nutrition source, temperature, pH etc.

4. Sources of xenobiotics Petrochemical industry : - oil/gas industry, refineries . 2. P lastic industry : - closely related to the petrochemical industry - uses a number of complex organic c om p oun d s - such as anti-oxidants, plasticizers, cross-linking agents

5. 3 . Pesticide industry : - most commo n ly foun d. - structures are benzene and benzene derivatives, 4. Paint industry : - major ingredient are solvents, - xylene, toluene, methyl ethyl ketone, methyl 5. Others : - Electronic industry, Textile industry, Pulp and Paper industry, Cosmetics and Pharmaceutical industry, Wood preservation

6. BIODEGRADATION OF PESTICIDES Pesticides  are substances meant for destroying any pest. They are a class of  biocide . The most common use of pesticides is as plant protection products (also known as crop protection products ). It includes: herbicide, insecticide, nematicide, termiticide,molluscicide , piscicide , avicide, rodenticide, insect repellent, animal repellent, antimicrobial, fungicide, disinfectant, and sanitizer.

7. DIFFERENT METHODS a) Detoxification :   Conversion of the pesticide molecule to a non-toxic compound. A single moiety in the side chain of a complex molecule is disturbed(removed), rendering the chemical non-toxic.  b) Degradation :   Breakdown or transformation of a complex substrate into simpler products leading to mineralization. E.g. Thirum is degraded by a strain of Pseudomonas  and the degradation products are dimethylamine, proteins, sulpholipids.

8. c ) Conjugation (complex formation or addition reaction) :   An organism makes the substrate more complex or combines the pesticide with cell metabolites. Conjugation or the formation of addition product is accomplished by those organisms catalyzing the reaction of addition of an amino acid, organic acid or methyl crown to the substrate thereby inactivating the pestcides. d) Changing the spectrum of toxicity :   Some pesticides are designed to control one particular group of pests, but are metabolized to yield products inhibitory to entirely dissimilar groups of organisms, for e.g. the fungicide PCNB is converted in soil to chlorinated benzoic acids that kill plants.

9. BIODEGRADTION OF PLASTICS Plastic refers to different polymers with high molecular weight. The biodegradation of plastics is done by microorganisms and enzymes. It consist of two steps- fragmentation and mineralization. The decomposition of major condensation polymers (e.g. polyesters and polyamides) takes place through hydrolysis. The decomposition of polymers in which the main chain contains only carbon atoms (e.g. polyvinyl alcohol, lignin) includes oxidation which can be followed by hydrolysis of the products of oxidation.

10. Different METHOD HYDROLYSIS - The process of breaking these chains and dissolving the polymers into smaller fragments is called hydrolysis. E.g. Pseudomonas. Polymeric Chains is broken down into constituent parts for the energy potential by microorganisms. Monomers are readily available to other bacteria and is used. ACIDOGENESIS - This results in further breakdown of the remaining components by acidogenic (fermentative) bacteria into ammonia, ethanol, carbon dioxide, and hydrogen sulfide. E.g Streptococcus acidophilus .

11. ACETOGENESIS - Simple molecules created through the acidogenesis phase are further digested by Acetogens to produce largely acetic acid, as well as carbon dioxide and hydrogen. METHANOGENESIS- Here, methanogens use the intermediate products of the preceding stages and convert them into methane, carbon dioxide, and water.

12. Some of the microorganism that can degrade plastics are:- Aliphatic Polyesters PolyEthylene Adipate (PEA ) - lipases from  R. arrizus , R. delemar , Achromobacter  sp. and  Candida cylindracea Poly ( β- Propiolactone ) PPL - estereases from  Acidovorax   sp.,  Variovorax paradoxus ,  Sphingomonas paucimobilis . Aromatic Polyesters Poly-3-Hydroxybutyrate (PHB ) – estereases from Pseudomonas lemoigne ,  Comamonas  sp.  Acidovorax faecalis , Aspergillus fumigatus Poly Lactic Acid (PLA ) - proteinase K from  Tritirachium album, Amycolatopsi s sp Strains of Actinimycetes has been reported to degrade polyamide (nylon), polystyrene, polyethylene.

13. BIODEGRADATION OF HYDROCARBONS A  hydrocarbon  is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are major constituents of crude oil and petroleum. It can be biodegraded by naturally occuring microorganisms in fresh water and marine environments under a variety of aerobic and anaerobic conditions.

14. POLYCYCLIC AROMATIC HYDROCARBONS (PAH ) Bacteria, fungi, yeasts, and algae have the ability to metabolize both lower and higher molecular weight PAHs found in the natural environment. Most bacteria have been found to oxygenate the PAH initially to form dihydrodiol with a cis -configuration, which can be further oxidized to catechols . Most fungi oxidize PAHs via a cytochrome catalyzed mono - oxygenase reaction to form reactive arene oxides that can isomerize to phenols. White-rot fungi oxidize PAHs via ligninases (lignin peroxidases and laccase) to form highly reactive quinones .

15. AEROBIC DEGRADATION Hydrocarbons easily degraded under aerobic condition. Alkenes and short-chain alkanes are the most easily degraded followed by branched alkanes and then aromatics.

16. ANAEROBIC DEGRADATION Often slower compared to aerobic. Process takes place in the absence of oxygen. Degradation process takes from days to months.

17. POLYCHLORINATED BIPHENYLS (PCB s ) Synthesized chemicals from petro-chemical industry used as lubricants and insulators in heavy industry. First manufactured in 1929 by Monsanto . Manufacture and unauthorized use banned in 1978 by USEPA Used because- Low reactivity Non-flammable High electrical resistance Stable when exposed to heat and pressure Used as Hydraulic fluid, Casting wax, Carbonless carbon paper, Compressors, Heat transfer systems, Plasticizers, Pigments, Adhesives, Liquid cooled electric motors, Fluorescent light.

18. RISKS - Causes reproductive disabilities in animals, human, birds. Carcinogenic Bioaccumulation Soluble in almost all the solvents, fats, oils Nervous system damage Endocrine gland malfunction

19. Methods for PCB removal Natural Attenuation : Microbes already in the soil are allowed to degrade as they can naturally and the site is closely monitored. Biostimulation : Microbes present in the soil are stimulated with nutrients such as oxygen, carbon sources like fertilizer to increase degradation. Bioaugmentation : Microbes that can naturally degrade PCB’s are transplanted to the site and fed nutrients if necessary .

20. reference www.slideshare.net www.biotecharticles.com www.environmentalrestoration.wiki www.wikipedia.org