The industry was receptive to the concept but was
skeptical of what was determined to be an even bigger advantage to
recovering the germ as a coproduct. Singh and Eckhoff saw that the
major advantage of the process was the removal of the germ from the
fermenter. By removing the non-fermentable germ, the space occupied by
the germ could be filled with additional degermed corn resulting in an
increase in sugar concentration at the same solids level. They
postulated that this should result in higher ethanol concentrations in
the beer, based on the work of Ingeldew (1999), who showed that with proper
yeast nutrition, ethanol concentrations as high as 23% were possible,
compared to the 12% commonly achieved by the industry at that time.
The process was enhanced by development of the
recovery of coarse fiber (pericarp) in the Quick Germ/Quick Fiber (QQ)
process (Wahjudi, et al, 2001). This addition to Quick Germ increased
the total nonfermentables removed from the fermenter and decreased the
concentration of fiber. Singh, et al. (2005) showed that the QQ process
not only increased the ethanol concentration in the beer but increased
the rate of ethanol production, validating the economic value originally
proposed by Singh and Eckhoff.
In the last several years, there have been a number
of other prefractionation procedures being proposed, with several even
being installed in selected plants. The alternative processes have been
mostly dry frac (for dry fractionation) processes which Murthy et al
(2006) has shown to suffer from stuck fermentations and slower
fermentations. Dry fractionation uses conventional dry milling equipment
to separate out the germ and pericarp fractions. Dry milling technology
is known to be inferior to wet milling technology in recovering clean
(low starch) fractions and appears to be more capital and energy
Maize Processing Innovators (MPI) licensed the QQ
process from the University of Illinois on an exclusive basis in 2006
and is currently bringing the technology to market.
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Singh, V. and S.R. Eckhoff. 1996. Effect of soak time, soak temperature and lactic acid on germ recovery for dry grind ethanol. Cereal Chemistry 73(6):716-720.
Singh, V. and S.R. Eckhoff. 1997. Economics of germ preseparation for dry-grind ethanol facilities. Cereal Chemistry 74(4):462-466.
Wahjudi, J., L. Xu, P. Wang, P. Buriak, V. Singh, M.E. Tumbleson, K.D. Rausch and S.R. Eckhoff. 2000. The "quick fiber" process: effect of temperature, specific gravity and percentage of residual germ. Cereal Chemistry 77(5):640-644.
Singh, V., D.B. Johnston, K. Naidu, K.D. Rausch, R.L. Belyea and M.E. Tumbleson. 2005. Comparison of modified dry grind processes for fermentation characteristics and DDGS composition. Cereal Chemistry 82:187-190.
Ingledew, W.M. 1999. Alcohol production by Saccharomyces cerevisiae: a yeast primer, In: The Alcohol Textbook (edited by K.A. Jacques, T.P. Lyons and D.R. Kelsall, Nottingham Press, Nottingham, England.
Murthy, G.S., V. Singh, D.B. Johnston, K.D. Rausch and M.E. Tumbleson. 2006. Evaluation and strategies to Improve fermentation characteristics of modified dry-grind corn processes. Cereal Chemistry 83(5):455-459.
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