Assessment of waxy and non-waxy corn and wheat cultivars as starch substrates for ethanol fermentation

The amylose/amylopectin ratio in cereal substrates is one of the parameters affecting starch hydrolysis and fermentation process. Waxy (less than 1 mass % of amylose) starch seems to be suitable for improving the fuel ethanol production. The main aim of this paper was to characterize the fermentation performance of corn and wheat waxy and non-waxy cultivars in terms of simultaneous saccharification and fermentation (SSF) as well as of the separated hydrolysis and fermentation (SHF) type. Two corn (waxy and non-waxy) and two wheat (waxy and non-waxy) cultivars were used for the comparison applying separate enzymatic hydrolysis and fermentation. In the SHF process, the glucose content was higher after saccharification in the waxy corn and wheat compared to that in non-waxy corn and wheat. In the SSF of waxy varieties, the glucose content after the pre-saccharification was also higher than in the non-waxy ones. Although the starch content did not vary significantly, differences in the glucose content after saccharification were observed. The ethanol yield obtained after the distillation of mash varied from 229.2–262.3 L per ton for the SHF fermentation, while it was in the range of 311.5–347.9 L per ton for the SSF process.