DisplayTitle

Germ-Derived FAN as Nitrogen Source for Corn Endosperm Fermentation

¹Agricultural & Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801. ²U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional, Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ³Corresponding author. Phone: 217-333-9510. Fax: 217-244-0323. E-mail: vsingh@illinois.edu ⁴Current address: Novozymes North America, Franklinton, NC 27525.

Corn endosperm separated by dry fractionation could exhibit poor fermentation performance due to loss of germ components beneficial for yeast growth. Inorganic nitrogen and other nutritional supplementations are used to overcome slow fermentation rates. We investigated the use of a protease in generating free amino nitrogen (FAN) from germ as an alternative to exogenous nitrogen sources. Up to 300% more FAN can be generated from germ in 6 hr of incubation with protease than without protease. Protease incubation also resulted in higher dry solids (ds) and total glucose contents in the germ hydrolyzates. During fermentation without urea addition, ethanol yields were dependent on mash FAN concentrations. Ethanol yields increased to a maximum when FAN level was 80–90 mg of FAN/100 g ds. At half the optimal FAN level (≈40 mg of FAN/100 g ds), nitrogen limitation occurred, as indicated by high residual glucose concentrations. However, germ FAN did not increase the ethanol yields compared to urea supplementation, likely because germ FAN resulted in lower substrate consumption compared to urea supplementation. Lower substrate consumption correlated to the increase in residual maltose with increase in initial FAN. Ethanol productivity in 0–24 hr of fermentation was higher with germ FAN than with urea, thus decreasing overall fermentation time.