Ethanol production from henequen (Agave fourcroydes Lem.) juice and molasses by a mixture of two yeasts

In the fermentation process of henequen (Agave fourcroydes Lem.) leaf juice, complemented with industrial molasses, the use of an inoculum comprising two yeasts: Kluyveromyces marxianus (isolated from the henequen plant) and Saccharomyces cerevisiae (commercial strain) was studied. An ethanol production of 5.22 ± 1.087% v/v was obtained. Contrary to expected, a decrease on ethanol production was observed with the use of the K. marxianus strain. The best results were obtained when a mixture of 25% K. marxianus and 75% S. cerevisiae or S. cerevisiae alone were used with an initial inoculum concentration of 3 × 107 cell mL−1. Furthermore, it was possible to detect a final concentration of approximately 2–4 g L−1 of reducing sugars that are not metabolized by the yeasts for the ethanol production. These results show that although the use of a mixture of yeasts can be of interest for the production of alcoholic beverages, it can be the opposite in the case of ethanol production for industrial purposes where manipulation of two strains can raise the production costs.