Evaluation of Two Sets of Sorghum Bagasse Samples as the Feedstock for Fermentable Sugar Recovery the Calcium Capturing by Carbonation (CaCCO) Process.

Sorghum bagasse samples from two sets (6 and 6; 18 and 18) of wild-type and corresponding "brown midrib" () mutant strains of sweet sorghum were evaluated as the feedstock for fermentable sugar recovery the calcium capturing by carbonation (CaCCO) process, which involves Ca(OH) pretreatment of bagasse with subsequent neutralization with CO for enzymatic saccharification. Saccharification tests under various pretreatment conditions of the CaCCO process at different Ca(OH) concentrations, temperatures or residence periods indicated that strains are more sensitive to the pretreatment than their counterparts are. It is expected that variant 6 is more suitable for glucose recovery than its wild-type counterpart because of the higher glucan content and better glucose recovery with less severe pretreatment. Meanwhile, 18showed higher scores of glucose recovery than its counterpart did, only at low pretreatment severity, and did not yield higher sugar recovery under the more severe conditions. The trend was similar to that of xylose recovery data from the two strains. The advantages of strains were also proven by means of simultaneous saccharification and fermentation of CaCCO-pretreated bagasse samples by pentose-fermenting yeast strain Cs 4R. The amounts needed for production of 1 L of ethanol from 6, 6, 18, and 18samples were estimated as 4.11, 3.46, 4.03, and 3.95 kg, respectively. The strains seem to have excellent compatibility with the CaCCO process for ethanol production, and it is expected that integrated research from the feedstock to bioprocess may result in breakthroughs for commercialization.