Bio(degradation/remediation/catalysis) Flashcards
Biodegredation
organisms do during metabolism, reduction of complex chemicals, can be complete or partial
Bioremediation
exploit biodegradation for clean-up purposes, remove unwanted chemicals or detoxify
Biocatalysis
exploit microbes for industrial use
Spill cleanup
hydrocarbon degrading microbes clean up sites- bioremediation
Complete Biodegradation
Mineralization- conversion of C,N,P,S and other elelments to inorganic products eg.CO2,NH4)
Partial Biodegradation
Biotransformation- transform compound to a more stable/less toxic/more useful compound
Principle of Microbial infallibility
no natural organic compound is totally resistant to biodegration in fav conditions
Xenobiotic
chemical that isnt normally found in a living organism or expected to be produced by it
factors influencing biodegradability/rate of biodegradation
pH, temp, organic matter content, availability of target compounds, only dissolved hydrocarbon units are available to degraders
Compound degradability depends on
element composition, structure: branching, repeating units, linkage, arrangement of substituents (more Cl- increases persistence)
Hydrocarbon biodegradation
degraders are found everywhere, most are aerobic using oxygenases
Methane and Hydrocarbon biodegradation
degraded my specialized C1 microorganisms (methanotrophs)
Aliphatics and degradation
- up to C9 can be toxic, biodegradable, volatile
- C10-C24 or branching decrease biodegradability
- unsaturated are more rapidly degraded than saturated
- (most to least degraded ) alkanes, aromatics, alicyclics
Beta - Oxidation of fatty acids
2C units (acetyl CoA) feeds into central metabolism (TCA Cycle) and reducing power (FADH, NADH), used to generate ATP or directly in biosynthesis
oxidation of aromatic hydrocarbons
-oxygenases (di- or mono-)
-initial steps lead to catechols, protocatechuate (aromatic rings with adjacent –OHs)
-subsequent ring cleavage between hydroxyl groups (ortho fission), beside the hydroxyl groups (meta fission)
eventual formation of compounds that enter central metabolic pathways (TCA cycle)
“funnelling” of many different aromatic compounds (including substituted aromatics) through a few key intermediates (e.g., catechols) to common pathways
anaerobic biodegradation of aromatic compounds
ring reduction followed by ring cleavage to form fatty acid
β-oxidation to acetyl-CoA & propionyl-CoA units
added oxygen is from H2O not O2
BTEX compounds may be slowly biodegraded by similar pathway in absence of oxygen
cometabolism
transformation of a substanve while a second serves as a primary growth substrate
Biocatalysis example
naphthalene dioxygenase catalyzes first step of aerobic naphthalene degradation
- has a broad substrate range, can be used for lots of catalysis
Biodegradation of xenobiotics
loss can be from biotic and abiotic reasons: volatile rxns, leaching, spontaneous decomposition, biological reactions
Reductive dechlorination
PCE or TCE, requires electrons + H+; Cl- is released
- cis-DCE is usual DCE intermediate in biological reduction
- this pathway occurs in anoxic, low redox environments
- microorganisms most efficient at this conduct dehalorespiration (chloroalkene = terminal electron acceptor in anaerobic respiration)
Biodegradation of 2,4,5-T by Burkholderia cepacia
- O2 required (i.e., oxic environments)
- note –Cl replacement by -OH
- note substituted catechol formation; subsequent ring fission
- note 2,4,5-T is used as a growth substrate; succinate, acetate feed into central metabolic pathways
Plastics
- polymers of polyethylene, polypropylene, PVC
- recalcitrant xenobiotic compounds
Biodegradable plastics
starch linked polymers, plastics based on microbial storage polymers
