Our technology
Our method for producing food-grade mycoproteins exploits the power of fungi fermentation to transform byproducts of the food industry into new nutritious foods. We discovered the best substrate-fungi match for our process based on the innovative submerged fermentation method. But what is submerged fermentation? And how does it differ from conventional fermentation methods?
Let’s find out.
Fermentation processes are crucial in various industries, including food, pharmaceuticals, and biotechnology. Two widely used techniques for producing fermented products are Submerged Fermentation (SMF) and Solid-State Fermentation (SSF). While both involve microbial growth, the key difference lies in the physical environment in which fermentation occurs.
submerged fermentation
Submerged fermentation is a method of cultivating microorganisms in liquid nutrient media. For industrial production, this implies growing the selected microorganism in closed vessels, called bioreactors, which contain nutrient broths (Ouedraogo & Tsang, 2021). This method is commonly used to produce enzymes, organic acids, yeasts, and industrial microbial biomass. One of SMF's advantages is that it is scalable, making it ideal for industrial applications requiring high microbial biomass or metabolite yields.
SMF is particularly efficient for processes where rapid microbial growth is needed, as the liquid medium provides an abundant supply of nutrients and oxygen. This makes it suitable for producing various enzymes and organic acids used in the food and pharmaceutical industries.
In SMF, microorganisms are inoculated into a bioreactor filled with a nutrient-rich liquid medium. Bioreactors allow the supply of oxygen as required for aerobic microorganisms and the ability to monitor and control different parameters such as pH, temperature, viscosity, dissolved oxygen, foam formation, biomass formation, substrate utilization and desired product formation (Xiong et al., 2012). The bioreactor’s size varies depending on the scale of production. One of the advantages of using bioreactors is the ability to sterilize them preventing contamination, allowing only the desired microbes to proliferate.
The process of creating mycoproteins for food production through SMF includes various steps:
1. Preparation of the culture medium:
The process begins with the preparation of a liquid culture medium, which contains sugars, minerals, nitrogen and other nutrients essential for the growth of the fungus. This medium is sterilised to remove any contaminants that could interfere with the growth of the fungus.
2. Inoculation:
Once the soil has been prepared, inoculation is carried out, i.e. the introduction of the selected fungal strain. The microorganism is chosen based on its ability to produce a biomass rich in protein and dietary fibre with a complete amino acid profile.
3. Fermentation:
The fermentation phase is the heart of the process. The culture is maintained under optimal conditions of temperature and pH, with a constant supply of oxygen. During this phase, the fungus grows and multiplies, forming a dense network of mycelia (threadlike structures that form the vegetative part of the fungus). Fermentation can last from a few hours to several days, depending on the specific conditions, the fungal strain and the desired product.
4. Biomass Harvesting and Treatment:
Once the desired density of fungal biomass is reached, the fermentation process is stopped and the biomass is separated from the culture liquid. The biomass is then subjected to various treatments, including washing, filtration, pasteurisation and dehydration, to remove any impurities and reduce the moisture content.
5. Formation of the Final Product:
The resulting biomass, rich in protein and with a fibrous texture similar to meat, can be further processed to form the final product. This can include mixing with other ingredients, texturisation, and forming food products such as burgers, meatballs, or alternatives to minced meat.
Solid-State Fermentation
Solid-state fermentation (SSF) differs from SMF by utilizing solid substrates without free-flowing aqueous phase. SSF is ideal for producing antibiotics, biofuels, and fermented foods, particularly for processes involving fungi and bacteria that thrive in low-moisture environments.
SSF mimics the natural environment of many fungi and some bacteria, allowing them to grow on solid substrates like grains, bran, or even inert materials impregnated with nutrients. This method is particularly beneficial when producing secondary metabolites and enzymes that are more effectively generated under limited moisture conditions.
In SSF, microorganisms are inoculated onto a solid substrate that can either be natural (e.g., wheat bran) or synthetic (e.g., materials impregnated with nutrients). These microbes extract nutrients from the substrate to produce valuable metabolites. Although microbial growth in SSF is slower due to limited water, the method often yields high-quality products, making it ideal for processes where secondary metabolites and complex enzymes are the targets.
SSF employs equipment such as tray fermenters, rotary drum fermenters, and fixed-bed reactors. Aeration is crucial in SSF since the microorganisms rely on oxygen for their metabolic activities. Fermenters are designed to allow air to circulate freely while maintaining stable temperature and humidity. Proper airflow and temperature control are essential to avoid microbial contamination and to promote consistent growth.
Differences Between Submerged and Solid state Fermentation
The primary distinction between SMF and SSF lies in the medium.
SMF uses a liquid medium that allows for faster microbial growth and higher yields of biomass, making it preferable for large-scale production of commodities like yeast and enzymes. On the other hand, SSF uses a solid medium, which encourages the production of secondary metabolites and enzymes at a slower rate, often resulting in higher-quality products.
SMF is best suited for applications that require rapid growth and high yield, such as citric acid production or the cultivation of industrial yeasts.
In contrast, SSF is ideal for food products that require longer fermentation times and controlled microbial activity, such as traditional fermented foods and bioactive compounds.
Submerged Fermentation (SMF) is currently applied for many types of food production including:
Monosodium Glutamate: Monosodium glutamate, a food additive used as a flavour enhancer, is produced by submerged fermentation by bacteria such as Corynebacterium glutamicum.
Citric Acid: Widely used as a flavour enhancer and preservative in food, citric acid is produced by Aspergillus niger using SMF. This method allows for the efficient production of large amounts of citric acid, which is a key additive in the beverage and food industries.
Enzymes for Dairy Products: Enzymes like rennet, used in cheese production, are frequently produced through SMF. These enzymes play a crucial role in coagulating milk, transforming it into curds for cheese-making.
Solid-State Fermentation (SSF) has also been exploited for various productions:
Tempeh: This traditional Indonesian food is made by fermenting soybeans with the Rhizopus fungus. Tempeh production uses SSF, where the solid substrate (soybeans) allows the fungus to develop fully, producing a protein-rich, nutritious food.
Miso: A staple in Japanese cuisine, miso is produced through the SSF process by fermenting soybeans with Aspergillus oryzae. The solid medium in this process provides a favorable environment for the growth of the fungus, resulting in a savory paste rich in umami flavor.
Cacao and Coffee Fermentation: Both cacao beans and coffee undergo SSF to develop their distinct flavors. This fermentation process is essential in determining the quality of chocolate and coffee, as the complex microbial activity enhances the aroma and taste of the final products.