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MICR 221 - Microbial Biotechnology.docx

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Department
Microbiology and Immunology
Course
MICR 221
Professor
Eric B Carstens
Semester
Winter

Description
Microbial Biotechnology  Microorganisms as agents of change (for the better) o Production of biofuels o Chemical intermediates Biofuels  Fuel ethanol o Transportation fuel made from renewable feedstocks o Oxygenate to improve combustion and reduce emissions  Contains more oxygen so burns cleaner, also at a lower temp. Reduces carbon monoxide and greenhouse gas emission. o Gasoline extender (energy independence, no longer need oil, etc.) o Used in 5-10% blends, as a flex fuel (E85)  85% ethanol, 15% gasoline o World ethanol production has been increasing rapidly since the 1970’s, especially to be used as fuel (as beverage has remained about the same, slight increase in industrial)  Largest increase in the United States (want fuel independence) o Sugarn can has the best energy balance, wheat and corn the worst.  Amount of energy input into the process compared to the energy released by burning the resulting product.  CO c2cle o Ethanol is a clean burning fuel (leaves little contamination) Fermentation Conditions  Saccharomyces cerevisae  Temperature below 34 centigrade  pH 4-6  Micro-aerobic conditions (concentration oxygen less than air)  Minimal additional nutrients required  Extensive heat evolution  Antibiotics (?)  Ethanol yield approx. 0.5kg EtOH/kg fermentable sugars Features of Ethanol Fermentation  End product inhibition (EPI): kinetic (doesn’t reach thermodynamic eqm) and process limitation  Fermentation vs. Recovery trade-off: recovery wins  Low productivity (efficiency)  A lot of water Solutions  Microbiology – Engineer a better organism via genetic/metabolic engineering o Ethanol tolerant yeast o High temperature yeast o C5 sugar fermenters o Fermenting organisms that produce hydrolytic enzymes, etc.  Biochemical engineering – design a better process Ethanol as a Microbial Biotechnology Process  Long standing, well-established process with societal and industrial acceptance  Provides public acceptance of other biofuels in future (e.g. biodiesel)  Multiple renewable biomass feedstocks  Still questions regarding food/fuel and energy balance  Cellulosic ethanol in near future (biofuel from wood, grasses, inedible plant parts)  Typical example of end product inhibition bioprocess Biobutanol and Aceton-Butanol-Ethanol (ABE) Fermentation  Butanol can be blended with traditional unleaded gasoline just like ethanol, but at larger concentrations than ethanol-gasoline blends.  Energy content of butanol is higher than ethanol and about the same as gasoline – will yield fuel consumption close to that of gasoline.  Evaporates more slowly than ethanol and vapours do not case smog.  Can be transported through existing pipelines for distribution since it’s less hygroscopic (absorbs water) than ethanol and is less susceptible to separation in presence of water.  When petrochemical production of solvents became easier and cheaper in the 1960s, fermentation processes began to experience a decline. Process features:  Anaerobic, usually use Clostridium acetobutylicum  Acid production (acidogenic) followed by solvent production (solventogenic)  A:B:E = 3:6:1  Slow (2 – 6 days)  The final total concentration of ABE solvents produced ranges from 12 – 20 g/L  End product inhibition! ABE Fermentation: Current trends Challenge Solution High feedstock cost significantly increase operating Transition towards cheaper (and more sustainable) costs feedstocks e.g. wastes and agricultural residues. Low butanol titres increase recovery costs, reduce Develop improved microbes with improved sugar loadings and increase water usage. solvent titres or develop methods for in situ product removal to alleviate end product tolerance. Low butanol yield increases feedstock costs. Develop improved microbes with higher butanol yields or higher butanol:solvent ratios. Low volumetric solvent productivities increase Develop continuous fermentation processes that capital and operating costs. reduce time and increase volumetric productivity Solvent recovery using conventional distillation is Develop low energy methods for solvent recovery energy intensive and relatively expensive. and purification. Recovery also improved by improving solvent titre. High water usage is not sustainable and increases Recycle process water back through the the cost of effluent treatment. fermentation. The Development of Antibiotics: A Paradigm fo
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