The different processes of industrial fermentation
Industrial fermentation can be carried out in various ways and through different processes that allow the control of cultures. Liquid medium fermentation processes are mainly distinguished by their operational method, particularly based on:
– The supply of the bioreactor (the tank where fermentation takes place) with substrate;
– The withdrawal of the bioreactor contents, which is the collection of the product and microorganisms (also called biomass) resulting from the fermentation.
Several fermentation processes exist.
- Batch fermentation
This process involves introducing microorganisms and the substrate into a closed bioreactor. During the fermentation period, no additional substrate or microorganisms are added, nor is there any withdrawal. The volume in the bioreactor remains constant throughout the process. The substrate is consumed by the microorganisms, leading to an increase in biomass concentration. Additionally, the substance of interest, which was absent at the beginning, appears and increases during fermentation.
- Fed-batch fermentation
Similar to the batch process, fed-batch involves continuous feeding, meaning the substrate is continuously added to the bioreactor without any withdrawal of the product. Initially, the substrate volume in the bioreactor is lower. Substrate is gradually added during the exponential growth phase of the microorganisms, causing the tank volume to increase. This extends the growth phase of the microorganisms. Substrate feeding is stopped once the tank is full, and the culture then proceeds similarly to batch fermentation. The product is harvested at the end of the process.
- Continuous fermentation
There are several types of continuous fermentation, the most common being the chemostat process. This method begins with a batch culture phase (without feeding or withdrawal) to promote biomass growth and ensure optimal production of the substance of interest. Then, there is a constant supply of substrate and a continuous withdrawal of the culture (biomass + products) at an equal flow rate. The volume in the bioreactor remains constant throughout the fermentation. The microorganisms are in a perpetual exponential growth phase due to the continuous substrate addition, ensuring maximum and ongoing productivity. Product and biomass accumulation is prevented thanks to the constant withdrawal during the process.
Among the different processes, there are liquid medium fermentation methods:
– Batch: no substrate feeding and no product withdrawal during fermentation;
– Fed-batch: continuous substrate feeding and no product withdrawal during fermentation;
– Continuous: constant substrate feeding and product withdrawal throughout fermentation.
There are also solid medium fermentation processes, where the substrate takes the form of a moist organic support.
Industrial fermentation: using living organisms for production
In addition to the process employed, the choice of microorganisms is essential in industrial fermentation, as each species or even strain has specific characteristics suited to the targeted production in various fields—food, health, flavors, etc.
These microorganisms use the substrate to produce: biomass (large-scale culture of microorganisms), metabolites (such as alcohol, organic acids, gases), or substances of interest (proteins, enzymes, flavors, etc.).
For example, in the food industry, yeast (particularly Saccharomyces cerevisiae) plays a key role in alcoholic fermentation, used in the production of beer, wine, or bioethanol, while lactic acid bacteria (Lactobacillus, Streptococcus) carry out lactic fermentation, essential for making yogurt, cheese, sauerkraut, or kefir.
In the flavors sector, industrial fermentation is notably used in the biosynthesis of natural aromas.
In the nutraceutical field, industrial fermentation enables the production of bioactive compounds, such as vitamins, as well as probiotics, for example, using *Bacillus subtilis*.
Industrial fermentation is also applied in the health sector, particularly for drug production. Recombinant bacteria (like *E. Coli*) are used to produce therapeutic proteins. Certain microorganisms are also used to produce antibiotics.
Natural flavors through fermentation: Ennolys’s expertise
For over 30 years, Ennolys has leveraged its industrial fermentation expertise to produce biomass and molecules of interest, notably in the field of flavors—specifically acetaldehyde and vanillin, with its Ennarom and Ennalin product lines.
By mastering fermentation processes (e.g., batch and fed-batch), Ennolys is able to optimize the production of natural aromatic compounds from selected strains of bacteria, yeast, and molds. This microbial diversity allows for great flexibility in achieving targeted metabolic and aromatic profiles.
Ennolys also places a strong emphasis on rigorous quality management, particularly in controlling cross-contamination, which is essential for ensuring production purity.
Beyond aromatic molecules, Ennolys’s expertise extends to providing clients with a wide range of microorganisms and their metabolites, including probiotics, postbiotics, enzymes, proteins, and peptides.
Industrial fermentation encompasses a set of processes that involve microorganisms to produce, on a large scale, a wide variety of compounds. The choice of process (batch, fed-batch, continuous, solid medium, etc.) depends on production objectives, as does the selection of microorganisms. Thanks to this technology, nature becomes a key player in sustainable production for food, health, energy, and chemistry.
