Conversion of Cheese Whey and Whey Permeate to Oil and Single-Cell Protein

Cheese whey and ultrafihration permeate were used as media for producing oil and single-cell protein with two strains each of the yeasts Candida curvata and Tricbosporon cutaneum.Optimum temperatures for cell multiplication and oil production by the four yeasts ranged from 28 to 33 C. Optimum pH's for cell multiplication were from 5.4 to 5.8. The optimum pH for oil production differed slightly from that for cell multiplication. Greater cell numbers were obtained if ammonium hydroxide was added to the medium, and mineral supplements also were sometimes stimulatory. Fermentation of whey by these organisms for 60 h reduced the chemical oxygen demand of the medium by a maximum of 85%, produced (depending on the organism) 6.3 to 9.3 g of oil/liter of whey, and left most of the protein unused. Fermentation of permeate for 72 h reduced chemical oxygen demand 95% and produced (depending on the organism) 4.0 to 15.6 g oil, 19.6 to 26.8 g cells, and 2.2 to 3.2 g single-cell protein/liter of permeate. The two strains of C. curvata were the most efficient in producing oil and reducing oxygen demand. The fat contained oleic (~50%), palmitic (~30%), stearic (%15%), and linoleic (~8%) acids. The cell protein was rich in methionine and other essential amino acids except that the two C. curvata strains were deficient in lysine.