Effects of medium glucose concentration and pH on docosahexaenoic acid content of heterotrophic Crypthecodinium cohnii

Abstract

The effects of medium glucose concentration and pH on growth and docosahexaenoic acid (DHA, C22:6 ω-3) content of Crypthecodinium cohnii were investigated. Over a range of glucose concentrations (5-40 g 1-1) investigated, the highest specific growth rate (0.12 h-1), highest cell dry weight concentration (3.13 g 1-1) and highest growth yield on glucose (0.6 g g-1) were obtained at 20 g 1-1 glucose. However, the highest degree of fatty acid unsaturation (3.2) and highest DHA proportion (53.4% of total fatty acids) were achieved at 5 g 1-1 glucose. Low glucose concentrations enhanced the degree of fatty acid unsaturation and DHA formation. Medium pH also affected cell growth, fatty acid unsaturation and DHA proportion. When medium pH was 7.2, the highest specific growth rate (0.089 h-1), highest cell dry weight concentration (2.73 g 1-1), highest growth yield on glucose (0.564 g g-1), highest degree of fatty acid unsaturation (3.4) and highest DHA proportion (56.8% of total fatty acids) were obtained. Results suggest that glucose concentration and pH value could be effectively manipulated to achieve maximum DHA production by C. cohnii. (C) 2000 Elsevier Science Ltd.