Handbook of Functional Lipids

fermentation technology, which is probably not less than $1000 per ton of biomass
generated, and we have an inherently expensive oil.

To produce microbial cells with an oil content of, say 50%, would probably cost

a minimum of $2000 per ton of cells (i.e., $4000 for a ton of oil). For an organism
with an oil content of 25%, where 4 tons of biomass would be needed, the fermen-
tation costs per ton of oil now rises to $8000. Thus the minimum cost of producing
1 ton of SCO cannot be much less than $4000 and could be as much as double or
even treble this if a slow-growing, low-yielding organism were to be used. To these
costs, the costs of oil extraction and refining have to be added and, though this may
not add much more than $500 per ton of oil, it still has to be taken into account.

From simple fermentation economics, only the most valuable of oils can thus

be contemplated for production. Using microorganisms to try to produce substitutes
for corn oil, groundnut oil, canola oil, or even cocoa butter is just not an economic
proposition. Therefore, one has to aim for much higher valued oils.

2.4 MICROBIAL OILS AS A SOURCE OF

-LINOLENIC

ACID (GLA)

2.4.1 GLA: S

OURCES

AND

PPLICATIONS

GLA (18:3, n-6) has a very long history of use, occurring as it occurs in the seed
oil of the evening primrose (

Oenothera

biennis

). Evening primrose oil (EPO) has

been used as a quasi-medicinal oil for centuries; it is known as “King’s Cure-All”
and thus has been recommended for the alleviation of a wide number of illnesses
[11–16], including the improved well-being of the elderly [17]. In the 1970s, it was
suggested as a possible treatment for multiple sclerosis, a claim that has since been
rescinded. Also at this time, EPO was regarded as highly useful for the relief of
premenstrual tension and also for the treatment of eczema, particularly childhood
and atopic eczema [15,16]. All these properties were attributed to the presence of GLA
in the oil, even though the amount of GLA in the oil being sold at this time was only
about 10%. GLA itself is a precursor of certain prostaglandins that fulfill essential
physiological roles in the body, and thus a continual

supply of GLA is needed to

ensure continuous synthesis of the prostaglandins, as they have only a short half-
life in the body. Normally, though, GLA is synthesized in the body from linoleic
acid (18:2, n-6) by a specific

∆

6 desaturase and supplementation of the diet should

be unnecessary. However, under certain conditions, the activity of the

∆

6 desaturase

may decline, leaving the body with a deficiency in GLA and therefore in prostag-
landins. Under such conditions, supplementation of the diet by oils containing GLA
has been advocated [11–17]; however, it has to be stated that the evidence is not
without its critics, and the efficacy or otherwise of EPO as a dietary supplement has
been questioned, principally because 90% of it is not GLA and whatever effects it
may bring about could be attributed to something other than GLA.

GLA, however, continues to be an attractive nutraceutical as a source of n-6 fatty

acids. Oils rich in this fatty acid are still recommended for the treatment or alleviation
of a number of clinical conditions: further information about the medical applications
of GLA may be found in two recent monographs devoted to this topic [13,14].

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