RESEARCH ARTICLE Comparison of Biochemical Activities between High and Low Lipid-Producing Strains ofMucor circinelloides: An Explanation for the High Oleaginicity of

The oleaginous fungus,Mucor circinelloides, is one of few fungi that produce high amounts of γ-linolenic acid (GLA); however, it usually only produces <25 % lipid. Nevertheless, a new strain (WJ11) isolated in this laboratory can produce lipid up to 36 % (w/w) cell dry weight (CDW). We have investigated the potential mechanism of high lipid accumulation inM. cir-cinelloidesWJ11 by comparative biochemical analysis with a low lipid-producing strain,M. circinelloides CBS 277.49, which accumulates less than 15 % (w/w) lipid.M. circinelloides WJ11 produced more cell mass than that of strain CBS 277.49, although with slower glu-cose consumption. In the lipid accumulation phase, activities of glucose-6-phosphate dehy-drogenase and 6-phosphogluconate dehydrogenase in strain WJ11 were greater than in CBS 277.49 by 46 % and 17%, respectively, and therefore may provide more NADPH for fatty acid biosynthesis. The activities of NAD+:isocitrate dehydrogenase and NADP+:isoci-trate dehydrogenase, however, were 43 % and 54%, respectively, lower in WJ11 than in CBS 277.49 and may retard the tricarboxylic acid cycle and thereby provide more substrate for ATP:citrate lyase (ACL) to produce acetyl-CoA. Also, the activities of ACL and fatty aci