The potential of agricultural banana waste for bioethanol production

Banana is one of the most important fruit crops around the world. After harvesting, it generates large amounts of lignocellulosic residues that could be used for second generation ethanol production. Optimal operating conditions of saccharification and fermentation processes, of the two main agricultural wastes of banana crop: pseudostem and rachis, for bioethanol production were selected in order attain conditions transferable to industry (optimizing resources and time). Both materials were previously pretreated with acid-catalyzed steam explosion. Full factorial experimental design was used in order to determine enzymatic hydrolysis process conditions to obtain glucose concentrations between 75 and 100 g.L−1. Optimal enzymatic hydrolysis conditions for rachis and pseudostem were 17.6% of solid loading and 16.0 FPU.g−1 glucan of enzyme dosage and 15.1% of solid loading and 14.9 FPU.g−1 glucan of enzyme dosage, respectively. The most suitable configuration to attain the highest volumetric ethanol productivity for rachis was 8 h prehydrolysis followed by a Simultaneous Saccharification and Fermentation (PSSF 8 h). Meanwhile, for pseudostem, higher ethanol production was obtained in Simultaneous Saccharification and Fermentation (SSF) configuration. At optimized conditions, pseudostem reached 112 L.t−1 of ethanol, and rachis 103 L.t−1. These conditions led to achieve ethanol production process at high solid loading, low enzyme dosage, low yeast inoculum, no mineral salts supplementation and maximum ethanol productivities.