Structural and physicochemical characteristics of taioba starch in comparison with cassava starch and its potential for ethanol production

Abstract

Starch is an important raw material in the fermentation industry for producing ethanol, which can then be used as renewable biofuel or as a basis for food, drink and pharmaceutical uses. Many tropical starch-producing plants are poorly exploited. Taioba (Xanthosoma sagittifolium) is a subsistence agriculture plant that has high starch content in its tubers but there have been few scientific studies for ethanol production to the present. The objective of this work was to evaluate the structural and physicochemical characteristics of taioba starch and its potential for ethanol production by comparing it to cassava (Manihot esculenta) starch, a well-known and commercially exploited plant. The starch content in the taioba and cassava were 65 and 80 % (DW), which had an amylose content of 21.80 and 23.65 % (DW), respectively. However, taioba starch had a lower proportion of short branched chains (DP 6−12), a higher proportion of intermediate branched chains (DP 13−24 and 25−36) of amylopectin (which are associated to the long term-retrogradation), smaller granule sizes and more densely packed and ordered crystals than cassava starch. It also had higher gelatinization temperatures and enthalpy change, lower peak and breaking viscosities, and a higher final viscosity compared to cassava starch. The hydrolysis (liquefaction and saccharification) reached 52 % and 50 % after 24 h, for cassava and taioba respectively. Maximum ethanol productions were 56 and 48 g/L, productivities were 0.67 and 0.56 g/L/h, yields were 0.49 and 0.46 and fermentation efficiencies were 96 and 90 %, for the cassava and taioba starches respectively. This study has improved understanding of the properties of taioba starch, as well its potential as a raw material for ethanol production.