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Background  Carbon sources for biofuel production are wide-ranging and their availability depends on the climate and soil conditions of the land where the production chain is located. Henequen ( Agave fourcroydes  Lem.) is cultivated in Yucatán, Mexico to produce natural fibers from the leaves, and a juice containing fructans is produced during this process. Fructans can be hydrolyzed to fructose and glucose and metabolized into ethanol by appropriate yeasts. In Mexico, different  Agave  species provide the carbon source for (distilled and non-distilled) alcoholic beverage production using the stem of the plant, whilst the leaves are discarded. In this work, we investigated the effect of thermal acid and enzymatic hydrolysis of the juice on the amount of reducing sugars released. Growth curves were generated with the yeasts  Saccharomyces cerevisiae  and  Kluyveromyces marxianus  and fermentations were then carried out with  Kluyveromyces marxianus  to determine alcohol yields.    Results  With thermal acid hydrolysis, the greatest increase in reducing sugars (82.6%) was obtained using 5% H 2 SO 4  at 100°C with a 30 min reaction time. Statistically similar results can be obtained using the same acid concentration at a lower temperature and with a shorter reaction time (60°C, 15 min), or by using 1% H 2 SO 4  at 100°C with a 30 min reaction time. In the case of enzymatic hydrolysis, the use of 5.75, 11.47 and 22.82 U of enzyme did not produce significant differences in the increase in reducing sugars. Although both hydrolysis processes obtained similar results, the difference was observed after fermentation. Ethanol yields were 50.3 ± 4 and 80.04 ± 5.29% of the theoretical yield respectively.    Conclusions  Final reducing sugars concentrations obtained with both thermal acid and enzymatic hydrolysis were similar.  Saccharomyces cerevisiae , a good ethanol producer, did not grow in the hydrolysates. Only  Kluyveromyces marxianus  was able to grow in them, giving a higher ethanol yield with the enzymatic hydrolysate. The leaves account for a non-negligible weight of the total agave plant biomass, so this work complements the knowledge already developed on agave fermentations by making it possible to produce ethanol from almost the entire plant (stem and leaves).

Hydrolysis of Agave fourcroydes Lemaire (henequen) leaf juice and fermentation with Kluyveromyces marxianusfor ethanol production