As early as from the very first meeting on, we expressed the urge to improve the environment and reform an every-day product we all use, but may be not aware of its environmental impact.
Therefore we all took 2 weeks of intense foundational research of every-day products we use, the amount of usage and their impact.
Quickly we had the insight that there is one nutritious, beloved, white, cold drink that is established in every social stratum all over the globe.
It‘s Milk! When we drink a cold, fresh glass of milk, nobody thinks about all the harm the production of this liquid causes.
More and more people become aware of the greenhouse gas (GHG) emissions livestock holding causes, but the vast majority does not know dairy cows make up the majority of it.
Yet we don’t want to miss out on a glass of nutritious milk or other dairy products.
So there was a need to find a solution that does not only improve the emission aspect, but also product-safety, optimizes nutrition, usability and is cruelty-free!
All the proteins and other nutrition sources contained in traditional milk, are of course inside our SynMylk in their purest forms.
Why? Because, unlike plant-alternatives, it’s identical to milk.
And you will never find any traces of antibiotics or other contaminants inside our SynMylk, which can also be lactose-free by default.
Description
Carbon efficient synthetic cow milk - SynMylk
As part of the international Genetically Engineered Machine (iGEM) competition, the team of the Heinrich-Heine University in Düsseldorf has put themselves to the task of creating cow’s milk without using any animal products. Dairy farming has a big impact on the environment due to the methane released by cows during their digestion. We seek to replace their milk with a product that is the same in taste, consistency and overall nutritiousness. Plant-based milk alternatives do not achieve the goal of replacing cow’s milk because they are too different in taste.
Our goal will be achieved using heterologous expression of proteins, enzymes, metabolic engineering, mathematical modelling and many other methods of synthetic biology. In all of these fields, we are supported with expertise by institutes in Düsseldorf and Jülich to make our project as successful as possible.
Cow’s milk is made up of lactose, lipids, proteins and nutrients, all of which are emulsified in water. Nutrients can be bought as pure chemical syntheses, but the proteins and lipids from milk are not commercially available without resorting to milk isolates. These two components are our focus.
Milk proteins are divided into two fractions of proteins, caseins and whey-proteins. Caseins are made up of four casein proteins (ɑ-s1-,ɑ-s2-, β- and κ-casein). Whey proteins contain hundreds of different proteins, so we will focus on the two most abundant ones (ɑ-lactalbumin and β-lactoglobulin). After a proof-of-concept production in E. coli we will use B. subtilis as our main production organism to secrete the proteins into its culture medium. Additionally, we will explore the cyanobacterium Synechocystis sp. PCC6803 as a host for protein production in a photosynthetic organism, yielding a net-reduction of CO2.
To produce the full range of lipids in milk, we further divided the production of lipids into long-chain (C14-C20) and short-chain (C4-C12) lipids, as long-chain lipids are produced naturally by most microorganisms, but short-chain lipids are not. Fatty acids, which make up lipids are synthesized in the cell in a circular process, extending a carbohydrate chain by two carbon atoms each time. A thioesterase enzyme terminates this process at a specific length, yielding a free fatty acid to be used in a triglyceride lipid.
Long-chain fatty acids are produced naturally by most microorganisms for their cell membranes. We will improve this natural process by overexpressing an enzyme for a rate-limiting step of fatty acid synthesis, the ACCase complex. This will be done in E. coli at first and later transferred into Synechocystis, which will produce the required lengths of fatty acids at no carbon cost.
Short-chain fatty acids are only produced by very few microorganisms containing thioesterases that terminate fatty acid synthesis at a short length. Four thioesterases from several organisms, including microalgae, plants and bacteria, will be heterologously expressed in Synechocystis. Since this bacterium also produces long-chain fatty acids, the endogenous thioesterase as well as other enzymes leading away from short-chain fatty acid synthesis will be down-regulated using a CRISPR knock-down.
