Performance of Saccharomyces carlsbergensis and Saccharomyces cerevisiae yeasts in the formulation of bioethanol from cashew apple residues

Abstract

Cashew tree is produced today mainly for its nut; the apple to which the nut is attached is neglected despite its richness in secondary metabolites and isn't consumed because of its astringency due to tannins presence. Indeed, its richness in fermentable sugars and in mineral elements and vitamins, makes it a substrate of choice in agro-resources bioconversion into bioethanol by fermentation. The present study aims to convert cashew apples residues into bioethanol by fermentative way in the presence of the yeasts: Saccharomyces carlsbergensis and Saccharomyces cerevisiae. The pressing residues of the cashew apples collected in the Center of Benin underwent an enzymatic hydrolysis. Monitoring the release of sugars, phenolic compounds and the Brix degree, as well as some optimization parameters, made it possible to better assess the efficiency of the processes. From results obtained, the hydrolyzate A1 presented a high content of total sugars (28.84g/L) and a high alcohol degree of (28.28 ± 1.03%) for a first distillation after fermentation. The best performance in ethanolic bioconversion was recorded in the presence of Saccharomyces carlsbergensis yeast. These investigations made it possible to highlight the potential use of these agro-industrial residues to produce bioethanol fuel.