2021 (10) : "Valorization of by-products of the food industry by fermentation process" (thesis by Justine Godard)

her thesis on theses.fr
Thesis Full text on HAL
• Thesis supervisor : Yann DEMARIGNY

• Funding : Terra Isara

• Partners :

 • Doctoral school : EDISS

The food industry, due to the transformation processes implemented, generates large quantities of organic waste annually. These products constitute a double loss for companies in this sector. Rarely valued, it is also necessary to ensure their reprocessing in order to reduce the environmental impact. Current reprocessing systems operate on anaerobic digestion or composting. However, the organic composition of these discharges must make it possible to envisage other recovery possibilities. Indeed, in the case of plant products, the directed use of fermentation processes can constitute a way of the future to be explored.

The general pattern of evolution of plant materials by spontaneous fermentations, in the natural state, goes through the succession of different microflora. Current technologies - wine, bread, sauerkraut, etc. - use part of these flora for food purposes. For example, lactic acid bacteria for sauerkraut or acetic flora for vinegar. However, with a few rare exceptions (cocoa), fermentations are carried out using a single microbial population, selected for productive needs. This leads to the generation, alongside the sought-after products, of new wastes with more or less high organic load.

Within the framework of the Terra Isara project, we propose to draw inspiration from the approach developed by Mickael Braungart ("cradle to cradle") to revalue the by-products of the food industry in cascade. It will no longer be a question of reasoning an organic waste on the basis of a single fermentation; but by integrating a dynamic (commensal) approach of different successive microbial flora, each helping to generate organic compounds of interest (chemical molecules - ethanol, acids, etc. -, enzymes, aromatic compounds, new foods for example). Thus at each stage, new compounds usable in food technology (or not) will be generated to be offered to different customers. But in addition, such a process would gradually reduce the organic load of the new waste generated. There is therefore successive value creation while reducing the environmental impact to obtain a very low amount of non-recoverable waste at the end of the chain. Especially since, we will try to reduce the share of water consumed from stage to stage of fermentation.

The work that we wish to undertake will integrate the search for optimal microbial consortia for each step and by integrating the next step according to the organic materials proposed. In addition, we will try to take into account two important aspects relating to the fermentation process: the recovery of heat resulting from fermentation and the use of an innovative statistical approach to control and predict the behavior of the whole system (approach Bayes).

The Terra Isara project is part of an objective to recycle waste, reduce losses and reflect on an ever closer integration of the food industry into sustainable development, which fully meets the expectations of the last COP21 . This is an extremely innovative project, both for its integrated approach to microbial ecosystems and for the originality of the methods envisaged to achieve it.