γ-Linolenic acid production by Cunninghamella echinulata growing on complex organic nitrogen sources

Growth of two strains of Cunninghamella echinulata on various nitrogen containing raw materials (corn gluten, corn steep, whey concentrate, yeast extract and tomato waste hydrolysate) yielded important amounts of biomass containing various quantities of γ-linolenic acid (GLA) rich cellular lipids. Especially, growth on tomato waste hydrolysate (TWH) yielded 17.6 g/l of biomass containing 39.6% oil and significant quantities of GLA corresponding to 800 mg/l GLA. Mycelium-bounded proteolytic activity was detected during early growth stages on TWH and declined thereafter, increasing the concentration of assimilable nitrogen in the medium. However, addition of glucose in the medium during the stationary phase triggered the biosynthesis of reserve lipid, since an increase of the proportion of neutral lipids from 45% to 79% in total lipids was observed, while polar lipids decreased from 35% to 12% and from 20% to 9% for glycolipids plus sphingolipids and phospholipids, respectively.