Co-Production of Ethanol from Starch and Cellulose in Corn during Simultaneous Saccharification and Fermentation

Abstract

First-generation (IG) ethanol production is corn starch to ethanol fermentation, and dosing cellulase at the beginning of the fermentation is termed in situ 1.5 G ethanol production. Co-production of corn starch and cellulose ethanol (1.5 G) was compared to a conventional 1G corn starch ethanol fermentation process to determine cellulosic ethanol yield. The analytical methods developed from this study for the quantitation of various modes of starch and cellulose will allow in situ 1.5 G ethanol producers to find the fraction of cellulosic ethanol eligible for D3 Renewable Identification Numbers (RINs). The fermentable starch, resistant starch (total starch minus fermentable starch), and cellulose were reduced in DDGS from 1 G to 1.5 G. Ethanol yield increased by 2% from 1G to 1.5 G. Among the 2% ethanol increase, more than half was cellulosic-based. This study developed high precision and accuracy analytical methods for quantifying various modes of starch and cellulose in corn matrix, which will allow corn ethanol manufacturers to find the fraction of ethanol eligible for the cellulosic ethanol credit.