Low-input fermentations of agave tequilana leaf juice generate high returns on ethanol yields

Abstract

During tequila production, up to 75 % w/w of the Agave plant is discarded when leaves are removed from the stem. The discarded leaves represent an extensive amount of unexploited biomass that was used here for bioethanol production in no-input fermentations, where no acid or enzymatic hydrolysis, supplementation of nutrients or standardization of carbohydrate content occur. Ethanol yield from Agave leaf juice is unaffected by sterilization but reduced if fermentation is reliant solely on endogenous microorganisms. Non-Saccharomyces yeasts, including Kluyveromyces marxianus and Candida akabanensis, proved to be more robust than standard Saccharomyces spp. and yielded up to 88 % of the theoretical maximum ethanol from leaf juice. Combining leaf and stem juice, as from a whole plant, was predicted to maximize yield at up to 19,439 L/ha of ethanol from mature plants.