Lactic acid from apple pomace: a laboratory experiment for teaching valorisation of wastes

Reutilisation and valorisation of wastes and byproducts is an increasingly important topic which can be illustrated at graduate or undergraduate level by the one-step bioconversion of apple pomace (AP) (an industrial byproduct) into lactic acid. A simple operational procedure that can be carried out without sophisticated equipment is proposed: starting from AP, hydrolytic enzymes and lactic acid bacteria present in yogurt, saccharification of the polysaccharides contained in AP and their fermentation into lactic acid are simultaneously carried out. During the process, the concentration profiles of sugars and lactic acid are measured. The experimental data provide the information needed for discussing basic aspects such as the kinetics of lactic acid generation and the lactic acid yield.