Biotechnological Studies for the Production of Arachidonic Acid from Mortierella Alpina

Mortierella alpina CBS 528.72, an oleaginous fungus and the most promising
source of arachidonic acid (ARA) was exploited for production of this nutraceutically
and pharmaceutically important polyunsaturated fatty acid (PUFA). Several physical
and chemical factors were investigated for their effect on biomass buildup,
oleaginicity and ARA yield. Results of the study indicated that these physical and
chemical parameters had a significant effect on biomass, total lipid and ARA yield in
this strain. Scale up study was carried out at 15L fermentor level subsequent to
optimization under shake flask conditions. One factor at a time (OFAT) and Response
surface methodology (RSM) proved to be efficient strategies for maximizing ARA
yield in M. alpina. Furthermore the use of corn solids as a cheaper alternative for
yeast extract reduced the cost of the process significantly.
Lipid extraction efficacy varied considerably with the mode of extraction,
solvent used and pretreatment of biomass. Mass transfer in intact cells of M. alpina
was hindered by hard natural membrane resulting in reduced lipid extraction. HCl and
enzyme pretreatment significantly increased the percentage of ruptured cells thereby
improving mass transfer of solutes and lipid extraction. Use of low temperature and
2, 3, 5- Triphenyl tetrazolium chloride enabled the selection of arachidonic acid hyper
producers from innumerable putative mutants. In spite of the set backs, random
mutagenesis still proved effective in isolating arachidonic acid hyper-producing
mutants of M. alpina. The safety of feeding M. alpina biomass was evaluated by acute
and subchronic toxicity studies in Wistar rats which indicated a favourable preclinical
profile of the biomass in safety evaluation. Cloning, sequencing and phylogenetic
analysis of 5 desaturase indicated that M. alpina 5 desaturase was phylogenetically
related to algal, slime mould and fungal desaturases with a conserved HPGG motif
and three characteristic histidine boxes at the cytochrome b5 region. These 5
desaturases were phylogenetically distinct from the animal 5
desaturases which
formed a strong cluster in itself indicating a later divergence than the fungal and plant
counterparts. In view of the above facts Mortierella alpina single cell oil can be
accepted as a biotechnological product fulfilling the key roles in the supply of
nutraceutically and pharmaceutically relevant polyunsaturated fatty acids essential for
infant and geriatric nutrition.