Evaluation of strategies for enhanced bioethanol production from melon peel waste

Abstract

Melon peels can be a low-cost raw material for the production of bioethanol due to its high worldwide production and contents in cellulose, protein and minerals. In this work, several strategies were proposed for this purpose. Centrifugation of the raw material and autohydrolysis of the washed solid were used as pretreatment for the recovery of a sugar rich juice and a glucan rich solid, respectively. The enzymatic hydrolysis of the autohydrolysis spent solid was studied by response surface assessment. High glucose concentrations (35.15 g/L after 24 h) and yields were obtained operating at a liquid solid ratio of 10 g/g and cellulase to solid ratio of 17.5 FPU/g. In the selected conditions, the simultaneous saccharification and fermentation (SSF) of the solid was studied using the juice (virgin and concentrated) in the formulation of the media. Moreover, the separate fermentation of the juice (virgin and concentrated) was also evaluated, as well as a pre-fermentation followed by SSF. Finally, several scenarios were proposed, achieving the maximum bioethanol production by SSF and separate juice fermentation (17.84 g/100 g melon peel), and the maximum concentration by SSF using concentrated juice in the formulation of the medium (56.24 g/L).