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Abstract

A. niger, a fungus which doesn't have high ability to produce lipid, has been selected to investigate its non-oleaginicity. In this search, there are explorations about: i) growth profile ii) enzyme profile iii) isoforms. Growth profile shows that this fungus doesn't have the ability to accumulate lipid more than 6%, while biomass is around 10g/l in spite of the presence of glucose in the media till the end of cultivation time and excision of nitrogen within 24 hrs. In enzyme study, we investigated all lipogenic enzymes: Malic enzyme (ME), Fatty acid synthase (FAS), ATP: Citrate lyase (ACL), NAD+ isocitrate dehydrogenase (NAD+ICDH), Glucose-6-phosphate dehydrogenase (G6PD), and 6-phosphogluconate dehydrogenase (6PGD). All these enzymes showed activities till the end of cultivation time, including ACL, which is regarded as the key enzyme to differentiate between oleaginous and non-oleaginous species. So, there is no main reason for non-oleaginicity for this fungus. A further experiment has been done using Polyacrylamide gel electrophoresis to identify ME isoforms. The result of Polyacrylamide gel electrophoresis shows multiple isoforms (A, B, C, D & E), with low intensity of isoform E, the isoforms that may be involved in lipid synthesis. We have now studied the biochemistry of A. niger grown under conditions designed to promote lipid accumulation and can now advance a coherent hypothesis to explain why A. niger could not accumulate lipid more than 6%. So, the absence of isoform E is the main reason for non-oleaginicity in A. niger.

Keywords

A niger, ME isoforms, lipid synthesis

Article Type

Supplemental Issue

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