Effect of Acetate and pH on Sunflower Oil Assimilation by Mucor circinelloides f. circinelloides

• Published in: Systematic and applied microbiology 1999-02, Vol.22 (1), p.156-160
• Main Authors: Jeffery, Jacqueline, Kock, Johan L.F., Du Preez, James C., Bareetseng, Andries S., Coetzee, Dennis J., Botes, Piet J., Botha, Alfie, Schewe, Tankred, Nigam, Santosh
• Format: Article
• Language: English
• Subjects: acetate; assimilation; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; biosurfactants; Biotechnology; cell culture; free fatty acids; Fundamental and applied biological sciences. Psychology; gamma-linolenic acid; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; linolenic acid; lipids; metabolism; Microbiology; Mission oriented research; Mucor; Mucor circinelloides; Mycology; Physiology and metabolism; sodium acetate; sunflower oil; γ-linolenic acid
• ISSN: 0723-2020; 1618-0984
• DOI: 10.1016/S0723-2020(99)80038-1

Mucor circinelloides f. circinelloides CBS 108.16 exhibited poor cell growth and substrate assimilation (32.5% of extracellular lipids) when grown with sunflower oil as sole carbon source. By contrast, in the presence of both sunflower oil (30 g/l) and sodium acetate (10 g/l), nearly complete utilization of both substrates (97.5% of sunflower oil, 100% of sodium acetate) occured and biomass production was increased about five-fold to 23 g dry weight/l after 72 h. A significantly higher content of γ-linolenic acid in the fungal neutral lipid fraction (5.2%) was also observed after 168 h of growth. These different patterns were attributed to the change in pH of the medium during cell growth in the presence and absence of acetate. In the absence of sodium acetate the pH decreased to 2.2, whereas in its presence it increased to about pH 8.0. During metabolism of sunflower oil in the presence of sodium acetate, the percentage of saturated fatty acids in the medium increased, suggesting a higher specificity of the fungal lipase for unsaturated fatty acids. For growth experiments in a small fermenter in the absence of sodium acetate, the gradual pH increase of sodium acetate containing medium was mimicked by an identical programme-controlled pH increase. Similar results as in the presence of sodium acetate were obtained. This observation indicated that the pH increase alone during cultivation was responsible for the increased sunflower oil utilization, biomass and GLA production.