Lecture 15: biofuels and biochemicals Flashcards
How did industrial fermentation begin
Acetone was in short supply in Britain during WW1 (was previously imported from germany) and was required for cordite production
Chestnuts were discovered for acetone productino
How was acetone produced using Clostridium
Produced in Clostridium acetobutylicum
ferments sugar to acetone, butanol, and ethanol (ABE Process)
Natural anaerobic process
Ethanol, acetone, and butanol secreted from cell (reduces costs)
What arae the main issues with usinig microbes for chemical production?
1 Cost
2 Genetic engineering a strain with stable chemical production
3 Mutation of genetically engineering strains
4 Scaling the process on an industrial scale
What compounds have always used microbes for production?
Organic acids
Amino acids
vitamins
How do we genetically engineer bacteria to improve compound production
Biosynthetic pathway has to be well characterised
What properties are important for producing chemicals?
fast growth
amenability for genetic manipulation
precursor production for desired chemical
ability to export chemicals from the cell
Where was the biosynthetic pathway for alkanes (hydrocarbon) found?
cyanobacteria
How is diesel produced from E. coli
Company: LS9
claimed the hydrocarbons were secreted into media, but they were adding small amount of detergent to lyase the cells.
Wasn’t commercially viable
NEW
Modified enzyme produced smaller FAs (ranging from C8 to C16)
These were able to be secreted
FINAL ENGINEERED STRAIN
Produced up to 580.8 mg/L(-1) of SCAs consisting of nonane, dodecane, tridecane, 2-methyl-dodecane, tetradecane
How was artemisinin in yeast synthesised
Artemisinin: anti-malarial drug derived from the plant Artemisia annua. Using this plant led to price and production variations from year to year
Used synthetic biology to express artemisinic acid pathway in Saccharomyces cerevisiae
PROCESS
1 upregulated production of precursor ‘farnesyl pyrophosphate’
(FPP)
2 Introduced Four novel genes for artemisinic acid production
3 Then gets secreted
Yield: 25g/L
Costs: 350-400$ per KG
How was artemisinin production process adapted for farnesene production
Farnesene - low value hydrocarbon which can be used as biofuel for chemical feedstock
Single enzyme required for production of farnesene from farnesyl pyrophosphate
‘Farnesene synthase’ introduced into yeast for production of farnesene
Low value: $3 per KG
To be commercially viable production has to be large scale and robust
PLANT USING BRAZILIAN SUGAR CANE WASNT COMMERCIALLY SUCCESSFUL AND WAS SOLD TO BE USED FOR HGH VALUE CHEMICAL PRODUCTION
What went wrong to the plant producing farnesene using Brazilian sugar cane?
Two likely possibilities:
1 upscaling
2 Mutation of strains
Upscaling problems include: mixing, aeration, cleaning, contamination, reusing yeast
What is the problem of evolution in genetically engineering bacteria
You are forcing bacteria to use energy and resources towards specific compound production instead of towards growth. Which isn’t to the organisms advantage.
THEREFORE THE STRAIN IS LESS FIT
Any mutant which rediverts energy and resources has a selective advantage.
How was the field of biochemical and fuel production recalibrated?
Focussing on higher value products
a. nutraceuticals (spirulina)
b. pharmaceuticals
c. specialty chemicals (smarties)
Improving production methods
Better strains
Unique products
What is the benefit of producing higher value compounds?
Solves two issues:
1. Upscaling from lab scale bioreactors with 10s to 100s of litres is
not as challenging
2. Genetic mutation is not as great an issue
a. can start with fresh starter cultures
b. cheaper to clean bioreactors
c. shorter culture periods
d. less cells
Success dependent on value of products: artemisinin ($350-400 per KG)
