Enzymatic hydrolysis of corn starch after extraction of corn oil with ethanol

Simultaneous corn oil extraction and alcohol dehydration, a solvent corn-milling process developed in our laboratory, was tested on a pilot scale to recover corn oil. Over 92% of the corn oil was extracted by 95% ethanol with a liquid-to-solid ratio of 0.75 at 65 degrees C. Following the oil extraction, 95% of zein fraction was also extracted from the defatted ground corn by 65% ethanol at 65 degrees C with a liquid-to-solid ratio of 1.0 to produce extracted ground corn. After corn oil and zein extraction by ethanol, the ability of the amylases to hydrolyze the starch fraction in extracted ground corn was studied. Results showed the starch fraction can be hydrolyzed to glucose by alpha-amylase and glucoamylase without separatio of fiber and residual protein. The glucose yield in hydrolysis was a function of temperature, enzyme concentration, and solid-to-liquid ratio. With a two-step heating hydrolysis, corn starch was converted to glucose with a 97.2% yield from extracted ground corn. After filtration and washing of the hydrolyzed mass, the final glucose concentration was 24.3% glucose (w/v).