Raw glycerol as substrate for the production of yeast biomass

Abstract

The possibility of using raw glycerol as a substrate for yeast biomass production as a source of proteins was investigated. Biomass concentration, protein content and total protein content of four yeasts (Yarrowia lipolytica NRRL YB-423, Candida lipolytica NRRL Y-1095, Candida utilis NRRL Y-900 and Candida rugosa NRRL Y-95) were determinate, comparing analytical grade glycerol and raw glycerol. Y. lipolytica NRRL YB-423 has been selected as promising for cultivation in a raw glycerol-based medium, mainly due to the higher biomass concentration in relation to the other strains. For this strain, four different culture media were tested. The best results were obtained with 50 g/L glycerol, 5.5 g/L ammonium phosphate, 5.5 potassium dihydrogen phosphate, 1 g/L ammonium sulphate, 0.25 g/L magnesium sulphate, 0.021 g/L calcium chloride dehydrate, 1 g/L yeast extract, 1 g/L peptone, pH adjusted to 5.5. In these conditions, it was possible to obtain 17.8 ± 0.6 g/L maximum biomass concentration, 18.2 ± 1.0% protein content and 3.1 ± 0.1 g/L total protein production. These results represent a 1.2-fold increase in biomass concentration, a 1.5-fold increase in protein content and a 1.9-fold increase in total protein production in relation to the results obtained with the previously medium composition.