Submitted to: Society for Industrial Microbiology News
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/21/2006
Publication Date: 3/21/2006
Citation: Murthy, G., Singh, V., Johnston, D., Rausch, K.D., Tumbleson, M.E. 2006. Improvement in fermentation characteristics of degermed ground corn by lipid supplementation. 2006. Journal of Industrial Microbiology Biotechnology 33:655-660. Interpretive Summary: With rapid growth of the fuel ethanol industry, and concomitant increase in distillers dried grains with solubles (DDGS, a dry animal feed coproduct), new corn fractionation technologies that reduce DDGS volume and produce higher value coproducts have been developed. One of these technologies, a dry separation process that removes portions that are not fermentable, also removes some components (lipids and other nutrients) that are beneficial to the yeast used to make ethanol. This results in the rate of production and the final yield of ethanol decreasing significantly. By adding different lipid supplements to the fermentation, we were able to identify some of the missing components and recover most of the fermentation rate and yield. These results will be useful to other ethanol researchers and producers using or evaluating dry fractionation processes and could help lower the production cost of fuel ethanol benefiting farmers and fuel ethanol consumers.
Technical Abstract: With rapid growth of fuel ethanol industry, and concomitant increase in distillers dried grains with solubles (DDGS), new corn fractionation technologies that reduce DDGS volume and produce higher value coproducts in dry grind ethanol process have been developed. One of the technologies, a dry degerm, defiber (3D) process (similar to conventional corn dry milling) was used to separate germ and pericarp fiber prior to the endosperm fraction fermentation. Recovery of germ and pericarp fiber in the 3D process results in removal of lipids from the fermentation medium. Biosynthesis of lipids, which is important for cell growth and viability, cannot proceed in strictly anaerobic fermentations. The effects of ten different lipid supplements on improving fermentation rates and ethanol yields were studied and compared to the conventional dry grind process. Endosperm fraction (from the 3D process) was mixed with water and liquefied by enzymatic hydrolysis and was fermented using simultaneous saccharification and fermentation. The highest ethanol concentration (13.7% v/v) was achieved with conventional dry grind process. Control treatment (endosperm fraction from 3D process without lipid supplementation) produced the lowest ethanol concentration (11.2% v/v). Three lipid treatments (fatty acid ester, alkylphenol, and ethoxylated sorbitan ester 1836) were most effective in improving final ethanol concentrations. Fatty acid ester treatment produced the highest final ethanol concentration (12.3% v/v) among all lipid supplementation treatments. Mean final ethanol concentrations of alkylphenol and ethoxylated sorbitan ester 1836 supplemented samples were 12.3 and 12.0% v/v, respectively.