Microbial Metabolism and Production Complete Summary
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Course
Metabolism and Bioengineering (MCB2022S)
Institution
University Of Cape Town (UCT)
Content covered includes:
- Microbial metabolsim including respiration and fermentation as well as metabolic pathways
- glutamic acid production
- lysine production
- citric acid production
• Macroelements = CHNOPS K, Ca, Mg, Fe
• Microelements = Mn, Mo, Zn, Cu, Co, Ni, V, B, Cl, Na, Se, Si, W
• Water!! à can measure required water amt via water activity
o Bacteria have high water activity levels
• Plants vs other orgs
o Photosynthetic production = linked to organic compound
mineralization
o Photosynthesis à use sun energy to liberate e- from H2O to power
oxidation and reduction of glucose
*large amounts of flexibility in use of C sources amongst microorganisms
• Prototrophs = microorganism requiring nutrients as most of the naturally
occurring members of its species
• Auxotroph = mutation in a prototroph that causes it to no longer be able to
synthesize a necessary growth factor (will require it to be supplied as a
nutrient)
• Nutrients in addition to C + energy sources, macroelements, microelements
= growth factors
1. Amino acids
2. Purines and pyrimidines
3. Vitamins (enzyme cofactors)
Nutritional Types
• Microorganisms require:
o Carbon source
§ Autotrophs = microorganisms using CO2 as sole carbon source
§ Heterotrophs = microorganisms that use reduced preformed
organic mols as C source
o Energy source
§ Light (phototrophs)
§ Chemical (chemotrophs)
• Derived from oxidation of organic/inorganic molecules
o Hydrogen ions
o Electrons
§ Organotrophs à obtain e- from oxidation of organic comps
§ Lithotrophs à oxidize inorganic compounds to obtain e-
• Eg. Methanogens (archaea)
*mixotrophs = chemolithotroph autotrophs (use an organic C source and obtain
energy from inorganic molecules
,Major nutritional types Sources of energy, Microorganisms
hydrogen/e-, carbon
Photolithotrophic Light energy Algae
autrotphy Inorganic hydrogen/e- Purple and green sulfur
donor bacteria
CO2 Cyanobacteria
Photoorganotrophic Light energy Purple and green non sulfur
heterotrophy Organic H/e- donor bacteria
Organic carbon source
Chemolithotrophic Chemical energy Sulfur oxidizing bacteria
autotrophy Inorganic H/e- donor Nitrifying bacteria
CO2 Hydrogen bacteria
Iron oxidizing bacteria
Chemoorganotrophic Chemical energy Protozoa
heterotrophy Organic H/e- donor Fungi
Organic carbon source Most nonphotosynthetic
bacteria (pathogens)
Energy
• Spontaneity is determined by whether ∆G<0
o ∆G<0 à free energy decreases, exergonic, energy is released
o ∆G>0 à energy requiring, endergonic
o ∆G=0 is at equilbiirum
• ∆Gº = standard state
o 1M concentration of H but that equates to a very LOW pH
• ∆Gº’ à determined at standard biological conditions so that pH = 7
Oxidation and Reduction (OIL RIG)
= those rxns in which e- are transferred from a donor to an acceptor (reducing agent
to oxidizing agent)
• Oxidation = loss of electrons
• Reduction = gain of electrons
Metabolism
= ordered transformation of molecules in the cell
à total of all chemical reactions occurring in the cell
o Energy conserving reactions (catabolism) and energy expending
reactions (anabolism)
• Nutrients acquired from the environment serve as energy sources for
metabolism
• Nutrients are transformed in a series of successive reactions via specific
metabolic pathways
• Enzyme catalyzed reactions
o Except for proline synthesis
• Function = provide precursors for synthesis of cellular components + provide
energy for biosynthetic and other energy requiring processes
• 3 major phases=
1. Catabolism à oxidative + exergonic
2. Synthesis of building blocks (monomers)
, 3. Synthesis of polymers
2 + 3 = anabolic, reductive + energy requiring (require electrons as a source of
reducing power à anabolism = reductive)
Funneling of nutrients
• Microorganisms can channel a wide variety of molecules into essential
processes
o à require unique uptake methods or:
§ Proteins
§ Polysaccharides
§ Lipids
• Default state of e- carriers = oxidized
o Catabolism = oxidative!
, Laws of thermodynamics
1. Energy cannot be created or destroyed
2. Entropy of the universe (system + surroundings) always increases in a
spontaneous reaction
Coupling of energy production and energy use
• ATP = mediator of anabolism and catabolism
• ATP generated via catabolism as nutrients are broken down
• ATP used in anabolism where precursors are made into products
o ATP has a very large –‘ve energy of hydrolysis to drive anabolic
reactions
o Does NOT mean that there is a significant amount of energy stored in
a bond
o Has high phosphate group transfer potential
Lecture 2
Standard half reaction = 2H+ + 2e- à H2 (Eº = 0)
• Assigned a standard [potential of 0V
For a spontaneous reaction: Eº>0
Eº à Eº’
• Standard reduction potential at pH 7.0 (biological pH)
• Overall reaction in e- transport in aerobic respiration à e- transport =
exergonic (spontaneous)
∆𝐺º! = −𝑛. 𝐹. 𝐸º!
Where n = number of e- transferred and F = 96400 J/V/mol
Unit for Gº’ = kj/mol
• Redox couples with more –‘ve reduction potentials donate e- to couples with
more +’ve potentials (greater affinity for e-)
• -‘ve electrode potential = better e- donor
• -”ve electrode potential = better e- acceptor
Breakdown of Carbohydrates
• Carbohydrates = main products of plant photosynthesis
o General nutrients for microorganisms
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