Biofuels Flashcards
What are biofuels
Renewable liquid or gaseous fuels made by and/ or from living organisms or the waste they produce
what are 2 main types of biofuels commercially produced
- Bioethanol
- Biodiesel
How is bioethanol produced
From sugar beet, sugar cane & corn by fermentation of soluble sugars (largely sucrose & glucose derived from starch) by the yeast Saccharomyces cerevisiae
How is biodiesal produced
By extraction of oil from soybean, rapeseed and palm crops followed by chemical esterification
What does the yeast enzyme invertase do in bioethanol production
Invertase converts sucrose to glucose & fructose
Glucose & fructose can both enter glycolysis
Sucrose can be added directly to fermentation vessel
In bioethanol production what is yeast degraded by and to produce what
- Degraded by amylases
- To produce glucose and other simple sugars
- Hydrolysis products are added to the fermentation vessel
What 2 microbes are used in bioethanol production
- Zymomonas mobilis
- Saccharomyces cerevisiae
Bioethanol production in terms of Saccharomyces cerevisiae
Saccharomyces cerevisae can convert glucose to ethanol via glycolysis
In bioethanol production what does glycolysis in yeast produce and where is the waste in this
- Produces 2 ATP for each glucose molecule & an increase in biomass
- An increase in biomass is wasted Carbon & energy which could have gone into ethanol production
How is waste in bioethanol production decr
Bioengineering of yeast allowd reduction of ATP yield (ATP = wasted carbon)
What bacteria reduces ATP yield & is used in bioethanol production
Zymmomonas mobilis
Biothenol production
In what way does Zymmomonas mobilis (anaerobic gram neg) break down glucose
Breaks down glucose via Entner-Duodoroff pathway
Bioethanol prod
What does Zymmomonas mobilis produce per glucose molecule
- 2 pyruvates
- only 1 ATP - less wasted carbon & energy
Bioethanol prod
What limits Zymmomonas mobilis broader usefulness
It can only use a few simple sugars - glucose, fructose & sucrose - for ethanol production
Bioethanol prod
Advantage of Zymmomonas mobilis over Sacchromyces cerevisae
Zymmomonas mobilis can withstand higher ethanol levels
Biodiesel prod
What is biodiesel comprised of
Fatty acid methyl and ethyl esters
Biodiesel prod
Does E. coli naturally produce triglycerides
No
Biodiesel prod
What can accumulate fatty acids as triglycerides? Can these be used directly as fuels
- Yeasts such as Saccharomyces cerevisae & some algae can accumulate fatty acids as triglycerides
- But these cant be directly used as fuels
Biodiesel prod
What has e. coli been genetically engineered to produce for biodiesel production
To produce fatty acid ethyl esters
Biodiesel prod
What has saccharomyces cerevisae been engineered to produce
To divert lipid synthesis away from triglycerides & into fatty acis ethyl esters
How do algae produce biofuels
Use energy from sunlight and CO2 to produce biomass including oil which can be converted into biodiesel
What are traditional/first generation crops made from
Edible crops
What are second or third generation biofuels made of
Non food crops or plant waste
what is much of the plant biomass from second/third gen biofuels made of
Mix of cellulose, hemicellulose and lignin known as lignocellulose
Advantages of second/third biofuels
Sources dont compete with crops grown for food
Production of 2nd and 3rd gen biofuels steps
- Solar energy collected by plants via photosynthesis and stored as lignocellulose
- Physical pre treatment (chemicals & enzymes) - decomposition of the cellulosic material into simple 5 and 6 carbon sugars by physical & chemical pretreatment
- Exposure to enzymes from biomass degrading organisms (fuel producing microorganisms)
- Simple sugars converted into fuels by microorganisms
Where are microbes that naturally produce cellulases found
In diverse environments - volcanic soil, termite guts and the stomach of cows
what can genetic engineering be used to expand the capabilities of in terms of microbes
Genetic engineering can be used to expand the capabilities of microbes to utilise sugars other than glucose and sucrose for ethanol production
What can biofuel compunds be used as
Automotive gasoline
Diesel
Jet fuels
