Co-Fermentation of Wheat and Whey Permeate for Ethanol Production and Chemical Characteristics of the Resulting Dried Distillers' Grains with Solubles

• Author / Creator

  Jin, Yiqiong

• The vast majority of global bio-ethanol production uses food crops as the primary feedstocks, which leads to the high dependence of ethanol production cost on the price of the crop-based carbon resources. The demand, and interests, to use cheaper non-crop-based carbon sources for the ethanol industry are increasing globally. Whey permeate, a residue of the cheese industry, can be a promising alternative feedstock for ethanol production. A major component in whey permeate is lactose which is a readily available fermentable carbon source. To investigate this possibility, the main goal of this study was to utilize whey permeate as a co-substrate to wheat for ethanol production. It is hoped that this approach will not only help alleviate the issues related to crop-based feedstocks for the ethanol industry but also create a profitable market to consume whey permeate for the cheese industry. In this study, whey permeate was used as a co-substrate to replace part of the wheat for ethanol production by Saccharomyces cerevisiae. The simultaneous saccharification and fermentation occurred with β-galactosidase added at the onset of the fermentation to conduct whey lactose hydrolysis. Aspergillus oryzae and Kluyveromyces lactis β-galactosidases were two enzymes selected and used in the co-fermentation respectively for the comparison of their effectiveness on lactose hydrolysis. Ethanol yield of the co-fermentation of wheat and whey permeate was evaluated. It was found that A. oryzae β-galactosidase was efficient for lactose hydrolysis during the co-fermentation and the ethanol yield efficiency was enhanced by the whey permeate supplementation. Due to the additional cost associated with the usage of soluble A. oryzae β-galactosidase, the possibility and reusability of immobilized β-galactosidase in the co-fermentation was investigated. The immobilized β-galactosidase was shown to be as effective as the soluble enzyme for the co-fermentation and can be reused for at least three cycles without compromising ethanol yield. Dried distillers’ grains with solubles is an important co-product from the ethanol production with dry-grind process, which substantially contributes to the economical and sustainable ethanol manufacturing. A comprehensive evaluation of chemical characteristics of the dried distillers’ grains with solubles produced from the fermentation of lactose containing batches was conducted. Differences in the chemical characteristics were observed between the dried distillers’ grains with solubles derived from the fermentation of wheat only and the co-fermentation of wheat and whey permeate. In summary, the supplementation of whey permeate contributed to ethanol production as a co-substrate to wheat with A. oryzae β-galactosidase added for lactose hydrolysis during the fermentation. The immobilized β-galactosidase can be effectively used in the co-fermentation with good reusability. Though the supplementation of whey permeate changed the chemical characteristic profile of the resulting dried distillers’ grains with solubles, the nutritional values were still within the range of the variations published.

• Subjects / Keywords

  • Wheat
  • Dried distillers' grains with solubles
  • Whey permeate
  • Ethanol production
  • Enzyme immobilization
  • Β-Galactosidase
  • Co-fermentation

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3XD0R58K

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.