The large quantities of serine are made from the bacterium Escherichia coli. The chemicals are created through a special culture technique which is based on cell line technology and which requires attending robots.
Serine is a ɑ-amino acid that is used in the biosynthesis of proteins. Its name is derived from the Latin for silk, sericum, which reflects the fact that serine was first obtained from silk protein back in 1865. The amino acid is important on several levels, not least for maintaining normal body function. Serine is important in metabolism as it participates in the biosynthesis of purines and pyrimidines, as well as other metabolites. The amino acid is one of twenty necessary for the development of bone in the human body.
In chemistry, serine plays a role in the catalytic function of many enzymes and it is used in some insecticides. In the pharmaceutical and cosmetics industries serine is used as a moisturizer; it also has cleaning properties. There is also a medical role, with a variant called D-Serine being studied in rodents as a potential treatment for schizophrenia.
Due to the industrial importance of the amino acid, scientists from The Novo Nordisk Foundation Center for Biosustainability have been attempting to prodcue the chemical on a large scale and in a sustainable way. The environmental importance is that serine has the potential to replace many chemicals extracted from the oil industry.
The new process to produce serine relies on bacteria. For this the research group who developed the process produced E. coli cells capable of surviving high concentrations of serine. They achieved this through a technique called ‘Adaptive Laboratory Evolution’ (or ALE). Adaptive laboratory evolution is a method used in biological studies to gain insights into the basic mechanisms of molecular evolution and adaptive changes, especially those that accumulate in microbial populations over the long term under specified growth conditions.
With the specific method, bacterial cells were exposed to a small amount of serine. Once the bacteria had become accustomed to these conditions, the organisms were transferred to a slightly higher concentration. This iterative process was repeated several times until optimal tolerance was achieved. This process used highly specialized robots to monitor and transfer the bacterial cells.
The tolerant bacteria were then genetically optimized to produce serine. In trials, 250 to 300 grams of serine can be produced for each kilo of glucose added to the bacterial culture. This is considered, in biotechnological terms, as a considerable yield. By using a relatively inexpensive sugar (glucose) the production costs are low.
In a research note, the lead scientist Professor Alex Toftgaard said: “This discovery is quite unique and proves that we can actually adapt cells to tolerate large amounts of serine — something many people thought wasn’t possible.”
The next step is to attempt to commercialize the process and to upscale production. The process is intended to challenge other, more costly, microbial based methods to produce serine, such as the process of converting glycine and methanol. Glycine is relatively expensive compared with glucose.
The findings have been published in the journal Metabolic Engineering, with the research paper titled “Increased production of L-serine in Escherichia coli through Adaptive Laboratory Evolution.”
Essential Science
This article is part of Digital Journal’s regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week looked at how some heartburn medications have a connection with stroke risk. Here the article looked at the biomedical factors. The week before we considered the farming of algae, as a potential super-food, was being developed through the use of sophisticated bio-reactors.
