Process options for conversion of Agave tequilana leaves into bioethanol

• Pretreatment of Agave tequilana leaves with sulphuric acid was investigated.
• Optimal pre-treatment condition was identified.
• Enzymatic glucose conversion of 70% was achieved.
• Leaf bagasse was fermented with 68% glucose to ethanol conversion.
• Fresh A. tequilana leaf juice was fermented without addition of enzyme.

This paper reports on mild acid pretreatment options for the conversion of Agave tequilana leaves into composite sugars for ethanol fermentation. The effect of five different pretreatment conditions (time, temperature and acid concentrations) were assessed in terms of cellulose digestibility, hemicellulose solubilisation and lignin content in leaves of 1.25 years old A. tequilana plants from Rockhampton and 2.5 year plants from Kalamia. Dilute acid pretreatment and enzyme saccharification of A. tequilana leaf bagasse significantly improved total glucose recovery. A recovery of 273 mg/g (70% theoretical) was attained when the bagasse was pretreated with 2.0% H2SO4 for 60 min at 121 °C and saccharified with 6% (w/w) CTec 2. Saccharomyces cerevisiae efficiently fermented crude A. tequilana bagasse and juice hydrolysates within 13 h and 7 h respectively, yielding up to 38.6 g/L and 12.4 g/L. This corresponds to glucose to ethanol conversion rate of 68 and 61% for A. tequilana leaf bagasse and juice, respectively. With further developments, including fermentation of C5 sugars and inulinase saccharification of juices (release of fructose), this process could deliver greater yields, reinforcing its potential as a biofuel feedstock.