By Dorte Larsen, AAU Communication and Public Affairs
Photos: Emil Kragborg Eriksen

At the AAU Department of Chemistry and Bioscience, Christian Enrico Rusbjerg-Weberskov is working on something that might sound like science fiction, but is actually a real solution to one of the biggest challenges of the future: How do we get enough protein for a growing world population without putting additional strain on the planet? Christian is a molecular biologist with a PhD from Aarhus University where he worked on skin diseases and protein chemistry. Today, he has switched tracks and is now investigating the fermentation of residues from the food industry – such as oat husks and spent grains from beer brewing – with the aim of creating new, sustainable foods.

"I got interested early on in how we can meet the need for high-quality protein in a sustainable way. Today, I devote a large part of my research time to fungi and their ability to convert residues into nutrient-rich foods. We have plenty of carbohydrates, but proteins play a central role in our nutrition. Fungi are an important source when we need to provide enough protein for everyone," he explains. 

Fungi as food factories

Christian works with filamentous fungi, edible species like Rhizopus oryzae and Neurospora crassa in particular, that can break down residues and convert them into edible – and tasty – products when fermented. The fungus Rhizopus oryzae is already used today to make the popular plant-based product Tempeh and is thus suitable for food. Tempeh is traditionally made by fermenting soybeans and has a nutty flavor and firm texture, a bit like meat.  In this type of fermentation, the fungus forms a white mycelium that envelops the substrate. Imagine French nougat where the sugar is replaced by the protein-rich tissue of the fungi. 

"The fermented product can be fried, ground into flour and used for baking, or used as an ingredient in things like sausages and biscuits. It contains fibre, carbohydrates, fats – and most importantly: proteins," says Christian.

From biogas to the table

Beer brewing is an example of an industry that produces large amounts of residues. In the production of beer, sugar and starch are extracted from barley kernels. What remains is a moist residue, called spent grains, which is now primarily used for biogas production and animal feed. Christian's research aims to move Danish residues, like spent grains and oat husks, up the value chain – into food for humans.

“If we can eat what we used to discard, we achieve optimal use of our agricultural land. This is one of the big wins. Another major benefit of fermentation is that it provides a tasty, umami-rich product that can be used in our diet as an alternative to meat," he says.

In collaboration with UCPH Food (Department of Food Science, University of Copenhagen) and the Danish Technological Institute, products such as sausages and crispbread with fermented ingredients have already been developed. The taste is characteristic and similar to rye bread, and, according to test subjects, both appetizing and recognizable.

Precision fermentation: The future of protein production

Another way Christian uses fungi is for precision fermentation. A new research project, UPCYFUN, focusing on this production method has just begun. Christian is part of the project and will investigate how fungi can best be adapted to precision fermentation, among other things. Specifically, fungi will be used to produce specific proteins, initially milk protein with sought-after nutritional and functional use. This is achieved by inserting a gene from the cow with molecular precision. 

The possibilities with this technology are many, as there are a number of proteins with their own sought-after properties. Some can foam, others can emulsify and others are 2000 times sweeter than sugar, all properties that are in demand by food manufacturers. With the same precision, fungi can be optimized to make exactly the protein that is in demand.  

"The climate benefits of the new technology are substantial. Specifically, we can make milk protein without cows, and even from a residue product. This is a major benefit, both environmentally and economically," says Christian.

A research field with a future

In his research, Christian investigates both the nutritional value and the functional use of the proteins, such as whether they can be used as foaming or emulsifying ingredients in the food industry. These functionalities are achieved today with animal-based ingredients like eggs and whey. But in the future, sustainably produced ingredients must be an option for the sake of the climate.

In a recently published article where Christian is the principal author, the conclusion is that protein extract from fermented spent grains has the potential to replace animal ingredients. 

"It's about making it concrete and usable, so that one day we can buy tasty, recognizable products in the supermarket that are made from what we previously threw away," he says.