Carbon source utilization and gamma-linolenic acid production by mucoralean fungi

The influence of 38 different carbon sources on growth and consequent gamma-linolenic acid [18:3(omega 6)] content of the lipids produced by four mucoralean fungal strains was investigated. The strains represented the species Mortierella alpina, Mucor circinelloides, Mucor flavus and Thamnostylum piriforme. The strains were cultivated in synthetic media, devoid of long-chain fatty acids, containing 2.00 g/l carbon. The biomass was periodically harvested, freeze dried and the total lipids were extracted. The long-chain fatty acids in the lipids were analysed as methyl esters by gas chromatography. Generally the highest per centages 18:3(omega 6), relative to other long-chain fatty acids, were obtained on disaccharides and polysaccharides as carbon sources, compared to other carbohydrates which include pentoses and trisaccharides. Higher percentages 18:3(omega 6) were obtained on alcohols as carbon sources in the case of the representatives of Mucor and Mortierella, and on organic acids as carbon sources for the representative of Thamnostylum?. The representatives of M. circinelloides and M. flavus respectively utilized 25 and 23 of the 38 carbon sources in the series. The highest percentages 18:3(omega 6) obtained with the representatives of M. circinelloides and M. flavus were 27.17% and 36.40% respectively. In contrast, the highest percentages 18:3(omega 6) obtained with the representatives of M. alpina and T. piriforme were only 5.61% and 12.84% respectively. These two strains could respectively utilize only 7 and 17 of the carbon sources.