Biotechnological Potential of an Autochthonous Microbial Consortium from Expired Dairy Products for Lactic Acid and Co-product Generation

Expired dairy products (EDP) can serve as a source of fermentative microorganisms for bioproduct generation. In this study, an autochthonous mixed microbial culture was successfully obtained from EDP using anaerobic batch reactors (100 mL) filled with 50 mL of All Purpose Tween (APT) medium and purged with nitrogen (99.99%), incubated at 37 °C for 48 h. The culture removed 93% of the glucose, producing 8.3 g L⁻¹ of lactic acid (LA) as the main metabolite, with a yield of 0.92 g g⁻¹. Microbiological and molecular analysis identified Lactobacillus as the dominant genus (78.4%). The culture also grew efficiently on various monosaccharides, disaccharides, and agro-industrial residues, including EDP and banana processing wastewater (BPW). LA was the predominant metabolite for all substrates tested, with maximum concentration from glucose (7.85 g L⁻¹) and the highest yield from BPW (0.98 g g⁻¹). Minor metabolites such as acetic acid, ethanol, isovaleric acid, isobutyric acid, and gases (CO₂, H₂) were also detected. These findings demonstrate the biotechnological potential of autochthonous microbial consortia for sustainable LA production from diverse organic wastes.Graphical Abstract