Effect of Culture Variables on Mycelial Arachidonic acid Production by Mortierella alpina

Effect of culture conditions on biomass, lipid,
and arachidonic acid production was investigated in the
oleaginous fungus Mortierella alpina CBS 528.72 under
shake flask conditions. Several factors have been found to
affect the biomass buildup and lipogenesis in this fungus,
complicated by the fact that different strains demonstrate
varying optimization conditions. Growth, lipid accumulation,
and arachidonic acid production in the strain investigated
were influenced by media, pH, temperature, carbon
source, nitrogen source, etc. The results indicated that the
most effective medium for growth and arachidonic acid
production was glucose yeast extract medium. The optimum
pH and temperature were found to be 6.5 and 28°C,
respectively. On the same weight basis, glucose was the
most efficient carbon source for biomass and lipid
production in this fungal strain which yielded 6.8 g/L dry
biomass and 40.2% (w/w) total lipid after 7 days of
cultivation. Maximum arachidonic acid (ARA) production
of 40.41% achieved in rhamnose-containing media was not
concomitant with higher biomass and lipid yields. Efficacy
of organic carbon sources, viz, yeast extract and peptone
over inorganic sources like sodium nitrate, ammonium
sulfate, ammonium chloride, etc, was established in the
present study. M. alpina CBS 528.72 grown in peptone
acquired the highest lipid content (42.0% (w/w)). However,
the ARA content (28.74%) proved to be significantly less
than that grown in yeast extract (35.28%). Furthermore, it
was found that the biomass and ARA production declined
drastically in a medium with vegetable oils as the sole
carbon source but triggered the lipogenic pathway leading
to higher accumulation of total lipids. Under the ideal
conditions mentioned above, the maximum biomass, total
lipid, and arachidonic acid production were 6.8 g/L, 41.6%,
and 35.28% total fatty acid, respectively, in shake flask
system.