The focus of our research is on protein production from bacteria for animal and human nutrition. The aim is to discover alternative protein sources and offer them as nutrition. It is important for our research that we use strains that grow with CO₂ as the only carbon source and produce edible proteins in larger quantities. In some cases, we also investigate side streams that serve as a carbon source for bacterial growth.

We are looking for suitable bacterial strains in the environment and have already found and isolated more than ten new strains. One group of microorganisms are so-called oxyhydrogen bacteria, which can produce up to 80 % protein in dry matter and whose amino acid profile is similar to that of animal proteins. But we have also found other strains that are not yet very well researched and are currently in the process of characterising these strains. Many of the strains grow in aerobic conditions, some prefer less oxygen in the gas mixture. The oxyhydrogen bacteria grow best with a lot of hydrogen. The most important criterion is that the strains grow with CO₂.

When it comes to bacterial strains that need to grow with CO₂, we use gas fermentation. We use different gas mixtures for this. These contain carbon dioxide, oxygen and hydrogen. As high concentrations of H₂ are required for this type of fermentation, special devices with explosion protection must be used. We are therefore currently limited in our experiments. When it comes to fermentation with liquid side streams, the fermentation conditions are much simpler.

At the moment, we are working on process optimisation, especially medium optimisation, in order to produce a lot of bacterial biomass with a high - up to 80% - protein content.

For some of our strains, we have tested a few side streams from fruit so far. These are, for example, juices and pomace from berries - ideally from those that contain large amounts of organic acids. We also plan to utilise other side streams in the future.

For the production of suitable proteins for animal and human nutrition, it is important to test the proteins for suitable amino acid profiles. A few criteria must be met here. The proteins should contain many essential amino acids that are crucial for healthy nutrition and our bodies. They should also be non-toxic and non-allergenic. In order to produce such proteins, bacterial strains must first be found that have the corresponding DNA sequence in the genome to do so. It is also possible to control the production of such proteins with targeted media optimisation. Downstream processes also play a major role in the production of edible microbial proteins.

We are not yet at the stage with our research where we can talk about specific applications. But there are companies that already have bacterial proteins for animal and even human food on the market. Bringing such proteins onto the market is not easy. They have to fulfil the requirements of the Novel Food Regulation before they can be marketed. So far, there are no authorised bacterial proteins (so-called single-cell proteins - SCP) for human nutrition on the European market. There is, for example, Quorn, a meat substitute made from special mushrooms, which is on the market in Singapore. 
It is also important to note that there are already bacteria that we eat, especially in fermented foods such as sauerkraut. However, these are processes that we have known about for a very long time and where we know that these bacteria ensure healthy intestinal flora. However, when it comes to completely new products, new strains that have not yet been used for such purposes, they need to be tested very thoroughly and in a variety of ways in order to ensure their safety and benefit for people.

Interview: Beatrix Boldt