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Development, scale-up and a continuous fermentation process for the cofermentation of cheese whey and corn for ethanol production
Abstract
Cheese whey was utilized as the liquid portion of a corn mash to supply 28% of the fermentable carbohydrate as lactose. A modified starch conversion process was developed wherein a fungal alpha-amylase was used to produce maltose from corn starch. Fermentation was accomplished using Kluyveromyces marxianus followed in 8 h by Saccharomyces cerevisiae in a staggered inoculation procedure. In laboratory trials, the whey-corn process produced 9.75% ethanol v/v in 72 h. Yields equivalent to 3.63 gal/bu resulted for the whey-corn process vs. 2.63 gal/bu for corn alone. The mixing power requirement during liquefaction of the whey-corn mash was reduced 20%. The whey-corn process was scaled-up to 6500 L runs using 5630 L of sweet whey permeate and 1243.7 kg corn per batch. K. marxianus was produced at the pilot plant in a medium of whey plus yeast extract. The whey-corn trials produced 9.3% ethanol v/v in 60 to 72 h. The pilot plant yield of 3.3 gal/bu for the whey-corn process was 96% of the expected yield while the control runs using corn alone yielded 2.6 gal/bu. The yield was increased by 27% using whey. The whey-corn cofermentation process was further modified to use acid whey (pH 4.3). Due to the high acid content, the liquefaction was performed at pH 5.0 and 5.5. Dextrose equivalents of 15 and 20, respectively, resulted for the starch portion of the mash, with no adverse effect observed upon fermentation. The acid whey-corn process was performed in 3800 L trials at a commercial farm-scale ethanol plant. Yields were increased by 25 to 29%. A two-stage continuous fermentation process was developed using whey permeate and corn starch at laboratory scale. The feed rate was 120 ml/h for a dilution rate of 0.12 h$\sp{-1}$ in the first vessel and 0.04 h$\sp{-1}$ in the second. In the first vessel, K. marxianus fermented lactose to 3.27% v/v ethanol. The second vessel could not maintain a stable population of S. cerevisiae which washed out in 48 h. Using K. marxianus as the sole yeast produced 6.9% ethanol v/v with an overall fermentation efficiency of 86%.
Subject Area
Food science
Recommended Citation
Whalen, Paul J, "Development, scale-up and a continuous fermentation process for the cofermentation of cheese whey and corn for ethanol production" (1987). ETD collection for University of Nebraska-Lincoln. AAI8810336.
https://digitalcommons.unl.edu/dissertations/AAI8810336