SR9068 - Treatment of Whey Permeate for the Production of Fuel Ethanol

Researcher:

Anna Crolla, Alfred College - University of Guelph

Objectives:

1. To develop a whey permeate where the BOD can potentially be reduced by 75%, while producing a value added product.

2. To investigate the feasibility of converting the lactose sugars in whey permeate to ethanol, in a cost-effective manner.

Expected Benefits:

1. The dairy industry will benefit by having available to them an alternative to the disposal of their whey permeate.

2. Transformation of whey permeate to a viable product such as ethanol offers an effective solution to the disposal problem of the permeate.

Summary of Research Results:

Kluyveromyces fragilis is the yeast culture being used in this investigation. Three yeast strains were compared, K.fragilis Y665, Y1195 and Y2415. An analysis of variance (ANOVA) was conducted on the fermentations conducted using the three different strains and it was determined that the obtained data supports that the strain of K.fragilis does have an effect on ethanol productivity. However, K.fragilis Y1195 did have the highest ethanol yield at 0.40 g ethanol/g lactose consumed, whereas K.fragilis Y665 and Y2415 produced relatively the same yields of 0.36 and 0.33 g ethanol/g lactose consumed, respectively.

From this study it was determined that extractive fermentation increased ethanol productivity by 400% from conventional fermentation with values of 1.55 ± 0.33 g/L h and 0.31 ± 0.03 g/L h, respectively. The ethanol yield also increased when extractive fermentations were conducted, with a yield of 0.40 ± 0.04 g ethanol/g lactose in conventional fermentation and a yield of 1.18 ± 0.25 g ethanol/g lactose in extractive fermentation when using K.fragilis Y-1195.

It has been determined that the initial concentration of ethanol in the feed has an effect on the flux across the membrane, and increased concentrations of ethanol in the feed results in a greater transport of ethanol across the membrane (higher flux). It was thus concluded that the extraction of ethanol from a fermentations should occur once there is at least 2-5 wt% of ethanol produced in the fermentation broth. In the fermentation of lactose to ethanol this concentration is usually reached after 48 hours, hence the extraction of ethanol should occur after this period.