Unlocking the potential of food industry by-products: Sustainable volatile fatty acids production via mixed culture acidogenic fermentation of reground pasta

The agroindustry generates substantial by-products each year, creating disposal challenges. In this view, this study focused on the valorisation of reground pasta (RP), a farinaceous by-product, towards the production of volatile fatty acids (VFAs), direct precursors to produce higher commercial value compounds (polymers, bioenergy or food conservatives), through mixed microbial culture (MMCs) fermentation. The RP solution contains high organic carbon (99 % volatile solids), which indicates strong potential for acidogenic conversion into fermented products. First, by using pre-treatments (water stirring, pH change, sonication and boiling) in batch mode, its hydrolysis degree was evaluated. After water stirring was chosen as pre-treatment, the RP solution thus obtained was fed to a lab-scale sequencing batch reactor (SBR). A conversion yield into fermentation products (FP) of 54 ± 2 % in terms of Chemical Oxygen Demand (CODFP/totCODin) was obtained with a concentration of 18.1 ± 1.0 g CODVFAs/L composed by 69 % odd (6.5; 3.8; 2.7 gCOD/L of acetic, iso-butyric and butyric acids, respectively) and 26 % even (4.0 and 1.0 gCOD/L of propionic and valeric acids, respectively) numbered C-atoms VFAs. Microbial community analysis revealed the dominance of Prevotella and Clostridium genera, which contributed to the production of propionic and acetic-butyric acids, respectively. These results, combined with the novelty of a pasta by-product valorisation through MMCs fermentation, unlock new pathways for sustainable waste valorisation and the production of high-value bioproducts.