CHEM 153L Lecture 14: Biofuels

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Biofuels
Fossil Fuels: a fuel formed in earth from dead plants/animal remains
Burning fossil fuels pollutes environment, so alternative energy sources necessary, like renewable
energy sources (solar, wind, water, geothermal, biomass)
Ex. coal, oil, natural gas
Biofuels: a fuel (as wood or ethanol) composed of or produced from biological raw materials
Various raw plant materials (either high in carbs or high in lipids) fed to microorganisms containing
enzymes for biofuel production:
o Rapeseed oil palmtransesterificationbiodiesel
o Sugar cane/sugar beetfermentationethanol
o Waste plant materialanaerobic digestionbiogas or fermentationtransest. alkanes,
alcohols, hydrogen, fatty acid alkyl ester
o Algaecultivation (directly produce fuel since perform photosynthesis)alkanes, alcohols,
hydrogen, fatty acid alkyl ester
Energy for biofuels comes from sunlight that plants convert to carbs via photosynthesis
Production of advanced biofuels: in industrial plants, microorganisms are cultivated in bioreactors and
fed with feedstock to convert to fuel molecules that can be harvested again
o Algae can be grown in illuminated bioreactors and no feedstock needs to be provided
Sources for energy during biofuel production:
o Disaccharide sucrose (glucose + fructose hexose) from sugar cane/sugar beet
How does it get digested to enter glycolysis?
Sucrose D-fructose and D-glucose via enzyme sucrose
Phosphorylation of D-glucose glucose-6-phosphate via enzyme hexokinase
Phosphorylation of D-fructose fructose-6-phosphate via enzyme hexokinase or
phosphorylation of D-fructose fructose-1-phosphate via enzyme fructokinase
Cleavage of fructose-1-phosphate glyceraldehyde and dihydroxyacetone
phosphate via enzyme fructose-1-phosphate aldolase
Dihydroxyacetone phosphate glyceraldehyde-3-phosphate via enzyme triose
phosphate isomerase
Phosphorylation of glyceraldehyde glyceraldehyde-3-phosphate via enzyme
triose phosphate isomerase to continue in glycolysis
o Polymer starch (glucose units linked via alpha 1,4 glucosidic bonds to amylose chains cross-linked
through alpha 1,6 branchpoints in amylopectin) from corn or potatoes
How does it get digested to enter glycolysis?
Cleavage of starch alpha 1,4 glucosidic bonds D-glucose via enzyme alpha
amylase
Cleavage of starch glucose-1-P units from non-reducing end glucose-1-
phosphate via enzyme phosphorylase
Switching of phosphate group from 1st to 6th position, going from glucose-1-
phosphate glucose-6-phosphate via enzyme phosphoglucomutase
Glucose-6-phosphate then continues through glycolysis
We can force microorganisms to produce ethanol by fermentation by growing them in absence of
oxygen (anaerobically)
o Without oxygen, cells cannot run citric acid cycle/oxidative phosphorylation but can undergo
glycolysis to produce 2 ATP and 2 NADH per glucose. NADH will build up and needs to be
oxidized to keep glycolysis running
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