The Influence of Different Strategies for the Saccharification of the Banana Plant Pseudostem and the Detoxification of Concentrated Broth on Bioethanol Production.

Pseudostem of the Musa cavendishii banana plant was submitted to chemical pretreatments with acid (H2 SO4 2%, 120 °C, 15 min) and with alkali (NaOH 3%, 120 °C, 15 min), saccharified by commercial enzymes Novozymes® (Cellic CTec2 and HTec2). The influences of the pretreatments on the degradation of the lignin, cellulose and hemicellulose, porosity of the surface, particle crystallinity, and yield in reducing sugars after saccharification (YRS ), were established. Different concentrations of biomass (70 and 100 g/L in dry matter (dm)), with different physical differences (dry granulated, crushed wet bagasse, and whole pseudostem), were used. The broth with the highest YRS among the different strategies tested was evaporated until the concentration of reducing sugars (RS) was to the order of 100 g/L and fermented, with and without prior detoxification with active carbon. Fermentation was carried out in Erlenmeyer flasks, at 30 °C, initial pH 5.0, and 120 rpm. In comparison to the biomass without chemical pretreatment and to the biomass pretreated with NaOH, the acid pretreatment of 70 g/L of dry granulated biomass enabled greater digestion of hemicellulose, lower index of cellulose crystallinity, and higher YRS (45.8 ± 0.7%). The RS increase in fermentation broth to 100 g/L, with posterior detoxification, presented higher productivity ethanol (QP  = 1.44 ± 0.02 g/L/h) with ethanol yield (YP/RS ) of 0.41 ± 0.02 g/g. The value of QP was to the order of 75% higher than QP obtained with the same broth without prior detoxification.