Rheological characteristics and genotype correlation of cassava root for very high gravity ethanol production: The influence of cassava varieties and harvest times

Abstract

In very high gravity (VHG) ethanol fermentation, the rheological properties of native cassava significantly influence heat and mass transfer, mixing energy, and, thus, the yield of all steps. This study investigated the effect of cassava varieties and their harvest times on starch liquefaction, saccharification, and fermentation. The genotype correlation of the starch properties was revealed for the most suitable cassava varieties. First, the starch content, amylose content, total reducing sugar from liquefaction and saccharification, pasting properties, and ethanol yields of six cassava varieties (Huay Bong 60, Hanatee, Kasetsart 50, Pirun 1, Pirun 2, and Rayong 11) at 6‐, 9‐, 12‐, and 15‐month harvest times were evaluated. The amylose content increased significantly from the 6th to the 12th month but slightly decreased at the 15th month. It was observed that the starch content contributed to a more substantial influence on the change in peak viscosity than on the amylose content. Ethanol fermentation using Saccharomyces cerevisiae TISTR5606 showed that the Rayong 11 variety at the 15‐month harvest time provided the highest ethanol concentration of 104.7 ± 4.1 g L−1 and an ethanol yield of 0.4 ± 0.1 g ethanol g−1 reducing sugar, which corresponded to 74.5% of the theoretical yield.

Histological and biophysical changes of cassava roots during retting, a key step of fufu processing

“…Moreover, the above findings indicate that the pasting behavior of cassava starch is genotype‐dependent. This finding was similar to those previously reported in several studies 36,40 . The pasting behaviour of cassava starch was also retting‐duration dependent, as previously reported 40,41 .…”

“…They were between 75.87 ± 1.01% and 80.33 ± 1.13% for starch, which is within the range of levels generally obtained in cassava root harvested after 12 months of growth in the field. The significant difference observed for starch at this stage between the varieties confirms the effect of genotype on the starch content of cassava as previously shown 36 . The level of amylose content ranged between 13.28 ± 0.19% and 15.79 ± 0.88% for amylose, which is lower than those previously reported 37,38 .…”

“…This finding was similar to those previously reported in several studies. 36,40 The pasting behaviour of cassava starch was also retting-duration dependent, as previously reported. 40,41 This pasting behaviour is probably linked to the rate of softening of the roots during retting.…”

“…The significant difference observed for starch at this stage between the varieties confirms the effect of genotype on the starch content of cassava as previously shown. 36 The level of amylose content ranged between 13.28 ± 0.19% and 15.79 ± 0.88% for amylose, which is lower than those previously reported. 37,38 One of the characteristics of cassava retting process is the cell wall degradation and root disintegration leading to the slight loss of material including starch released into the quenching water, which becomes cloudy and whitish.…”

Editorial for the special issue on “Metabolic engineering”

“…The paper by Sakdaronnarong et al. [6] reminds us the importance of the characteristics (e.g., sugar content, recalcitrance) of the biomass used as feedstock for the efficiency of first‐ and second‐generation biorefinery processes. Mazzoli [7] has reviewed the opportunities and challenges of metabolic engineering strategies aimed at direct fermentation of lignocellulose to lactic acid, a compound with several applications including the synthesis of biodegradable plastics.…”