Optimal conditions of acid-catalysed steam explosion pretreatment of banana lignocellulosic biomass for fermentable sugar production

BACKGROUND: Banana is one of the most cultivated fruit crops around the world. After its harvest, it generates large amounts of agricultural wastes. The objective of this study was to optimise the operational conditions of steam explosion pretreatment of the two main banana lignocellulosic residues, rachis and pseudostem, in order to achieve high overall sugar yields. RESULTS: A response surface statistical model (2(2) + star points with triplicate at central point) was used for the optimisation, considering the enzymatic hydrolysis yield and the overall yield of glucose and xylose as main criteria. The optimal conditions of steam explosion pretreatment for pseudostem were established at 177 degrees C, 5 min and 2.2% H2SO4 (v/v), presenting a high overall glucose yield of 91.0%. For rachis, the optimal conditions were 198 degrees C, 5 min and 1.5% H2SO4 (v/v) with an overall glucose yield of 87.1%. CONCLUSION: Optimal conditions for steam explosion pretreatment of agricultural banana wastes were determined. An acid-catalysed pretreatment was needed due to the low presence of acetyl groups in both feedstocks. After rachis pretreatment, extractives, soluble ashes and hemicellulose were solubilised causing an enrichment of cellulose in the insoluble fraction. However, due to the high amount of starch in pseudostem, a significant amount of glucose was recovered in the liquid fraction. (C) 2017 Society of Chemical Industry