Fermentation as a strategy to produce high value-added compounds from by-products and waste

One-third of food produced worldwide is lost or wasted every year and this became an economic, ethical, and environmental problem. Waste and by-products are generated along the entire food supply chain and, as a result, have led the United Nations to introduce regulations to reduce losses. In this context, it is introduced the concept of circular economy that means reuse, repair, and recycling the existing materials and products, closing the loop and giving value to waste materials. There are several ways to obtain value-added compounds from by-products and it refers to the bio-refinery techniques which is emerging as a sustainable option in the scientific community. As food waste is rich in nutrients, it can support the growth of a variety of microorganisms, and several studies focused on the microbial fermentation of different by-products to obtain different value-added compounds like organic acids, aroma compounds, and antimicrobials. Among the variety of possible starters to conduct fermentation processes, lactic acid bacteria (LAB), with recognition as Qualified Presumption of Safety (QPS)-status by EFSA, are the most important microorganisms associated with fermentation and thus exploited for industrial bioprocesses. Recently, the exploitation of LAB strains to valorize by-products and waste into high value-added products has been described but their potential on bio-transformations is still an untapped biotechnology resource. Different metabolites of industrial interest, such as bioactive molecules, can be produced by lactic acid fermentation starting from low-cost substrates. Solid-state fermentation offers several advantages such as low cost, simple equipment, and most importantly, it permits the use of agricultural and agro-industrial by-products as substrates. The use of these materials as the culture medium of microorganisms represents a potentially significant reduction in the cost of bioprocesses and the conversion of the waste into products with commercial value-added. In this context, the PhD thesis was divided into two main activities: the first one is the screening of different lactic acid bacterial strains for the modification of aromatic profile, while the second one is the production of antimicrobial compounds during fermentation and the study of optimization models to evaluate their use in food industry.