For thousands of years, people across the globe have been engaging in the age-old practice of fermenting local plant and animal raw materials. Initially, the primary purpose of fermentation was to ensure the preservation of these materials, a crucial factor for the survival of nomadic communities. However, in modern times, the focus has shifted towards the desirable textural qualities, health benefits, and taste enhancements associated with fermentation. From supermarket shelves conquered by kimchi, kombucha and co, to star chefs experimenting with the tongue-twisting delights of fermentation that give their best dishes a sour, umami-like taste - fermentation is undoubtedly in vogue. This trend comes in handy as fermented foods hold an untapped potential for innovation.
Scientists are not only conducting experiments on fermentation technologies to secure vital food supply during the early stages of Mars colonization (1), but also on Earth, the increased adoption of these technologies could serve as an elegant solution to address significant challenges concerning public health and the sustainability of contemporary diets and food systems.

Sustainability is one of the key aspects why scientists and manufacturers have become increasingly interested in fermented foods. According to the EAT Lancet Commission, one of the key factors for more sustainable and healthy diets in western countries is to consume a largely plant-based diet and to decrease the intake of animal source foods (2). Currently, traditional animal-based proteins are the major protein source, although their production has been characterized to be mostly unsustainable, and their consumption is often associated with health issues (3). At present, 40% of European consumers try to reduce their meat consumption and to replace them by plant-based foods (4). A crucial barrier to even wider adoption of proteins sourced from plants seems to be the negative perception of the taste and hedonic experience of plant-based foods, which are perceived as less satisfying compared to animal-based foods (4). Yet fermentation could come to the rescue, as it can add new flavours and textures to foods such as legumes, cereals, vegetables and fruits, and create exciting, novel and yet natural foods, thus increasing the appeal of these plant-based foods categories to consumers. In addition, fermentation is a process that requires little equipment, keeps waste in check and eliminates the need for additives to preserve food. Moreover, it can contribute to the idea of a circular, artisanal economy by producing nutritious, value-added foods from agricultural waste such fruit pomace, surplus, and imperfect produce and utilizing local and seasonal produce, thus enabling the preservation of abundant harvests, reducing reliance on long-distance transportation, and sustaining livelihoods in rural communities.

Health is another factor of paramount importance in the realm of the food transition. Our current food systems largely fall short in providing support for health-promoting diets. This can be witnessed merely by looking at the alarming increase in lifestyle-related diseases in Western societies, such as obesity, Type 2 diabetes, heart disease, and some types of cancer (5). Due to the presence of functional microorganisms, fermented foods possess unique characteristics that can impart health benefits to consumers. Human nutrition studies on the relationship between fermented food consumption and health were able to show, for example, that…

• …the risk for cardiovascular disease is inversely associated with the consumption of fermented dairy products (6)
• …the consumption of Kimchi counteracts the development of type 2 diabetes and obesity (7)
• …fermented dairy consumption improves relational memory (the ability to remember associations between objects, people or events) (8)
• …a fermented-food diet increases the diversity of gut microbes and decreases molecular signs of inflammation (9)

Certainly, fermented foods exhibit distinct qualities when compared to their original counterparts. This phenomenon becomes apparent when examining fermented foods derived from legumes and cereals, which hold significant importance in global diets and food security. Extensive research has revealed that these fermented foods exhibit elevated levels of essential nutrient (such as protein, amino acids, vitamins, fatty acids, etc.), decreased antinutritional compounds, and improved nutrient bioavailability (10) in comparison to their original food matrix. Lastly, incorporating fermented foods into dietary habits presents a powerful avenue for positively shaping the gut microbiome through two distinct mechanisms. Firstly, fermented foods provide a source of nutrients that can selectively promote or inhibit specific members of the gut microbiome. Secondly, these foods introduce microorganisms from the fermentation process that interact and engage with the resident gut microbiome. This dual effect holds immense potential to beneficially influence the composition and functionality of the gut microbiome (11).

Understanding the challenges and opportunities in fermented food research and engaging all food system actors in the process (from farmers to small and big food processors, food distributers and retailers, food waste processors and consumers) could facilitate the increased inclusion of fermented foods into current diets.

Existing challenges include:

• Limited scientific evidence of the positive impact of fermented foods on the human gut microbiome and health, which restricts relevant dietary recommendations (12)
• A lack of a comprehensive understanding of how microorganisms interact with the food during the fermentation process, which is needed to enhance functional and preservation properties (13).
• Exploring the immense natural biodiversity of microorganisms and identifying whether some of them might have interests that are still unknown today (14).
• A disconnection and lack of collaboration between stakeholders and key actors, impairing short-term innovation potential and long-term food sovereignty (15).
• Consumers’ lack of trust in food processing technologies and new food microbial solutions (16)

Yet the rise of plant-based fermented foods is now more realistic than ever, thanks to recent advancement in analytical techniques, such as high-throughput DNA sequencing technologies, that allow for the acquisition of genomic, metagenomic, transcriptomic, and metataxonomic data pertaining to the microorganisms associated with fermented foods. This wealth of information enables the assessment of individual strains and their potential as starter cultures within the fermented food industry (11).

To take advantage of these and other opportunities and meet the challenges of innovation in the field of plant-based fermented foods, a transdisciplinary team involving researchers, industrial players, and even citizens are getting into gear through the EU-funded project DOMINO. In short, the project aims to:

• Identify health biomarkers related to the consumption of fermented foods in a healthy population and in people with metabolic syndrome
• Integrate existing and novel knowledge with computational tools to predict key microbial activities during food fermentation. This will allow to design microbial consortia for the development of functional, healthy fermented foods with targeted properties
• Create plant-based fermented food prototypes with nutritional and sustainable added value and engage relevant actors (policymakers to farmers, and consumers) in the co-design of these novel foods

The DOMINO project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement No 101060218 (17).