Ethanol Production from Soursop Leachate: Nitrogen Sources and Scale-up

Soursop (Anona Muricata Lin.), a tropical fruit native to Central and South America, is recognized for its rich composition of water, sugars, proteins, vitamins, minerals, and dietary fibre. Despite its potential for food and dietary supplement production, approximately 30% of the Colombian soursop production is discarded due to non-compliance with regulated standards for this highly perishable fruit. This has prompted research into utilizing these discarded residues for ethanol production through fermentation processes. In this study, the feasibility of ethanol production from soursop leachate was assessed on a laboratory pilot scale. The investigation focused on the use of low-cost inorganic nitrogen sources, namely ammonium sulphate, ammonium chloride, and urea. Additionally, three distinct scale-up methodologies Reynolds number, volumetric power, and impeller tip speed were evaluated in working volumes of 0.5 and 5 L. A comprehensive rheological and hydrodynamic analysis was conducted using native yeasts. The results revealed that ammonium chloride, at a carbon/nitrogen ratio of 15/1, demonstrated the highest yields, reaching 0.33 g/g. Furthermore, the study indicated that employing volumetric power with increased agitation enhanced biomass production in 4.85 g/L, while impeller tip speed with moderate agitation resulted in higher ethanol production, yielding 0.28 g/g. These findings underscore the versatility of soursop in ethanol production and emphasize the significance of selecting an appropriate scale-up methodology aligned with production objectives. The implications of this choice on the achieved yields are substantial, emphasizing the importance of tailored approaches in optimizing ethanol production from soursop leachate.