On an industrial scale: How the biotechnological production of proteins and vitamins can be profitable

Under the buzzwords ‘power-to-protein’ and ‘power-to-vitamin’, biotechnological processes are being developed in which microbes use energy derived from basic chemical building blocks such as carbon dioxide, water and oxygen to produce proteins and vitamins for human consumption – entirely without livestock farming or agriculture. Environmental biotechnologist Professor Lars Angenent from the Cluster of Excellence ‘Control of Microorganisms for the Fight against Infections’ (CMFI) at the University of Tübingen has already optimised such a process in the laboratory, which produces not only proteins but also vitamin B9 (folic acid).

His team has now investigated whether this process – which is unique in that it is a two-stage process using two different microbes in sequence – can be scaled up to industrial production in a technically and economically viable manner – with positive results: A production plant capable of supplying 5.6 million people with the daily dose of vitamin B9 at market prices, whilst also contributing to protein intake, would pay for itself after just five years of operation. The study was published in the journal PNAS.

The growing world population and global warming are posing major challenges for conventional agriculture. Livestock farming, in particular, requires a great deal of resources and contributes significantly to the release of environmentally harmful substances. According to United Nations estimates, as early as 2023, 733 million people – just over nine per cent of the world’s population – were suffering from malnutrition. “It is to be feared that this figure will rise further. In poorer countries in particular, protein requirements cannot be met,” says Lars Angenent. The human body cannot produce all the essential nutrients itself and is dependent on the intake of certain proteins and vitamins.

Electricity prices have a major impact on overall costs

Energy is required in the power-to-protein and power-to-vitamin plants to operate the bioreactors – liquid tanks in which the microbes convert the supplied raw materials into the desired products under controlled conditions, such as constant temperature and pressure. Furthermore, the production of free hydrogen from water requires energy. In Angenent’s two-stage bioreactor system, the bacterium Thermoanaerobacter kivui reduces carbon dioxide to acetate using hydrogen in the first production step, carried out in the absence of air. The bacterium is undemanding and produces the folic acid required for acetate production itself. Subsequently, baker’s yeast – a fungus called Saccharomyces cerevisiae – converts the acetate into proteins in the presence of air. “The yeast itself, enriched with proteins and folic acid, is directly edible. Taken in small daily quantities as a dietary supplement to meet vitamin B9 requirements, it is a safe foodstuff,” says Angenent. “If the entire protein requirement is to be met using microbially produced proteins, the yeast must be purified to remove, for example, substances that can trigger gout. In that case, the production process is correspondingly more complex.”

The two-stage bioreactor plant, with a volume of 1,750 cubic metres, as outlined in the biotechnology research team’s sample calculation, could produce 12.9 kilotonnes of yeast annually, containing 813 kilograms of folic acid and 5.6 kilotonnes of protein. This quantity is sufficient to provide 5.6 million people with the recommended daily intake of folic acid and five per cent of their protein requirements. At a selling price of 20 US dollars per kilo of the enriched yeast, the production plant would pay for itself within five years. “According to our calculations, the minimum selling price required for economically viable production is determined primarily by the price of electricity and the energy required for electrolysis, through which the hydrogen is produced,” says Angenent. “Under ideal conditions, the price could be reduced to US$4.53 per kilo if, for example, there were no costs involved in producing the carbon dioxide and the yeast production rate could be further increased.” If the two-stage process is used primarily to provide people with a complete protein supply, the yeast must be heat-treated for purification. “This would increase the minimum selling price to US$14.24 per kilo of yeast; at a price of US$20, the plant would pay for itself after seven years.”