CO₂ as Biological Feedstock Flashcards
Photosynthesis accounts for how many gigatonnes of carbon being sequestered from the atmopshere every year?
120 gigatonnes
ATP is formed in the light dependent part of photosynthesis
It is then used to do what?
ATP is used to drive the calvincycle in the light independent reaction which allows the sequestration of CO₂, to form sugars and structural materials (as well as forming O₂ as a byproduct)
Photosynthetic organisms (plants, algae, cyanobacteria) convert around 120 petagrams of carbon into biomass a year
Why is this impressive biological process?
CO₂ is considered to be a thermodynamic sink
Hence the biology is quite impressive because it is using CO₂ to form sugars and whole range of other molecules
What can be some industrial applications of yeast?
Yeast can be engineered to be used in the preperation of a variety of products including (EtOH) beer and wine, small molecules and biofuels (BuOH and GVL)
As well as large scale use in food, brewing industry
(engineered yeast are key to sustainable use of biomass)
Explain biocatalysis in terms of the critic acid cycle?
- A whole cell biocatalysis brings together many different processes and reactions
- Engineering allows control of different pathways to produce certain molecules
- The citric acid cycle takes the products of photosynthesis and channels them into different hydrocarbon which the plant will use
- Many of the compounds found later on in the cycle can be used as chemical precursors for industrial chemicals
- Industrial biotechnology using appropriate understanding + editing can be used to created specific molecule of intrest
Many of the biological cycles (like Krebs cycle e.g.) are strictly controled by enzyme and equilibrium based reactions which promote/suppress certain reactions
How can scientists hence affect how much of a biological molecule is being made in one of these cycles for example?
By variation of the genetic code within an organism, we can promote or suppress a particular chemical pathways
We can design microorganisms to deliver a function
How do the classical fermentation industrial processes occur?
- It is a biological method of making molecules through fermentation
- Would usually take feedstock (hexose) with minerals and co-factors and introduce them to the yeast.
- Then let them grow in the fermentation broth
- The organisms will grow and produce molecule up to a certain point (beyond this it is toxic), the isolate the product
What is the big issue with the classical fermentation process?
- Not so great for continous chemcial processes
This is due to only being able to make small concentrations (5-8% in solution) and you can’t intensify that material to make many thousands of tonnes - The supply of carbon atoms will come from things like sugar (shouldn’t divert materials which we grow as food into chemicals)
- it would need to a continous process to gain the right scale
What is the benefit of using gas fermentation instead?
- it is a great way to move away from the food vs chemicals to use a completely different source of carbon
- This can be done by using industrial waste gases that come from otherwise existing processes (CO₂, CO, CH₄, H₂) and would usually be flared
- Go on to form products like ethanol and reduce life cycle emissions (which can be used in fuels etc)
What is the benefit of putting ethanol into fuels?
Ethanol can be incorporated into petrol/gasoline which would upgrate it through isomerisation/polymerisation to make higher calorific value molecules
The ethanol is coming from preexisting carbon sources rather than newly refined peterochemicals
Give an example of how gas fermentation could be applied to a pre-existing industrial process
You can produce ethanol from steel mill off-gas (already produces 150 million tonnes of CO₂)
Source of carbon is very abundant and help close the loop on carbon
87% reduction in life cycle emissions
How have the company LanzaTech utilised gas fermentation
- LanzaTech has created a series of processes which uses the off-gases in the feedstock and fermentation
- The fermentation themselves run at very high efficiency and lead to generation of really high amount of ethanol
- Ethanol can then be recovered from the aqueous fermentation broth, separated from the biomass culture, distilled, and sold off as a primary chemical/additive to petrol
Clostridium is a genus of an organism which was originally isolated from rabbits
How was it been engineered to reduce dependancy on petrochemical processes
- This organism feeds on a mixture of 1C gases (CO₂, CO, CH₄) which can be used as a feedstock for the generation of a whole series of different molecules
- we can edit the processes within the cell to channel carbon towards a particular product
- But through engineering within the organism, you can form much more elaborate structures which have higher value within the chemical feedstock chain
Name some examples of bulk and commodity chemicals which can be produced through gas ferementation using Clostridium and other similar organisms like cyanobacteria and algae
Aromatics, isobutylene, 1,3-butadiene, propylene, ethylene
(and others)
In a previous example, LanzaTech used simple gases from Steel Mills which are then converted into ethanol
What further chemistry can occur after this?
- Downstream chemistry can dimerise and dehydrate ethanol into butadiene which can be distilled and sold
- Butadiene can be used as a precursor for the polymer used in tired, nylon and in pharmaceuticles
