3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
(C17 : 0, Supelco, USA). Fatty acid concentration was evaluated
with ChemStation software B0103 (Agilent technologies,
USA).
Results and Discussion
The extensive research and development of PUFA production
by SSF is basically aimed at improving the economic
competitiveness of that microbial process compared to
plant- and animal-derived oils. Emphasis is put on increasing
the product value, using inexpensive substrates, screening
for more efficient strains and reducing the processing steps.
Therefore, it is necessary to optimize the potential of microorganisms
for transformation of agroindustrial materials and
oil residues into desired metabolites.
Screening of microorganisms has led to selection of
T. elegans, C. echinulata, C. elegans and Mortierella isabellina
as producers of GLA 6,9 and Mortierella alpina as a
producer of DGLA, AA and EPA 10 . Generally, the surface
of substrates was not only covered by the fungal mycelium
during cultivation, but the fungal hyphae also penetrated into
the substrates. Thus, fungal PUFAs were accumulated in the
newly formed bioproduct and their amount depended on the
substrates, microorganisms and cultivation conditions used.
Depending on the microorganism, various types of cereal
substrates were employed during SSF experiments (Table I).
Spent malt grains (SMG) served as an internal support. Substrates
without SMG in most cases led to agglomeration of
substrate particles and created more compact mass which in
turn interfered with microbial respiration and affected substrate
utilization negatively. Presence of SMG improved
bioconversion of linoleic acid from substrates to GLA 9 . Substrates
with internal support not only provided better respiration
and aeration efficiency due to an increased inter-particle
space but also helped to remove the heat generated during
fermentation. It should be noticed that although PUFAs were
synthesized more effectively by SMG addition to substrates,
total PUFAs yield was also dependent on substrate/SMG
ratio. Unbalanced substrate/SMG ratio might provide limited
surface for microbial attack and thus poorer availability of
assimilable compounds (including oils) from substrates.
Growth of fungi on a carbohydrates-containing substrates
resulted after optimization of cultural conditions in constant
lipid yield with the demanded fatty acid profile. Further
improvement of PUFAs formation was achieved by physiological
regulation of the SSF process employing following
steps 10 : a) gradual elevation of carbon/nitrogen ratio with
addition of appropriate carbon source; b) optimization of
water activity, temperature and oxygen availability; c) transformation
of exogenously added oils consisting of precursor
of PUFAs. There is a stock of relatively cheap vegetable
oils containing individual fatty acid precursors and SSF was
applied for microbial utilization of renewable agricultural
oils with the aim to modify their properties for production
of value-added bioproducts with enhanced biological characteristics.
Thus the ability of the strains to utilize exogenous
fatty acids opens new possibilities to prepare PUFAs in high
s545
yield. Moreover, because fungi possess active oil-biotransforming
system, these strains were also tested for their ability
to convert directly oil-rich substrates (corn, sunflower seeds,
linseeds, rapeseeds) to PUFAs.
Table I
Production of γ-linolenic acid (GLA), dihomo-γ-linolenic
acid (DGLA), arachidonic acid (AA) and eicosapentaenoic
acid (EPA) by solid state fermentations of selected fungi utilizing
various cereal substrates. Ratio of susbtrate/SMG was
1 : 3 (w/w)
Strain Substrate PUFA Yield
[g kg –1 BP]
T. elegans oat flakes/SMG GLA 5.9
wheat bran/SMG GLA 5.0
wheat bran/SMG/
GLA 10.0
sunflower oil
crushed corn GLA 10.0
rye bran/SMG GLA 4.2
buckwheat/SMG GLA 4.7
millet/SMG GLA 6.5
amaranth/SMG GLA 4.7
C. echinulata barley GLA 6.1
C. elegans barley GLA 7.0
M. isabellina barley GLA 18.0
M. alpina rice AA 21.4
wheat sprout/SMG AA 36.1
wheat bran/SMG AA 42.3
rye bran/SMG AA 21.9
peeled barley AA 16.2
oat flakes AA 31.2
M. aplina cresed sesame seeds DGLA 21.3
M. alpina peeld barley/linseed EPA/AA 23.4/36.3
oil/SMG
Biosynthesis and profile of fatty acids is controlled by
enzymes involved in lipogenesis, so activation or inhibition
of these metabolic steps is also useful tool for improving carbon
flux to individual PUFAs 11 . For example, bioconversion
of DGLA to AA is catalyzed by ‚∆ 5 ‘ desaturase and inhibition
of this enzyme by crushed sesame seeds was accompanied by
rapid increase of DGLA/AA ratio 11 ). In addition, application
of various plant extracts possessing bioactive compounds
seems to be promising way how to regulate fatty acid biosynthetic
machinery in order to gain bioproduct with high
yield of preferred PUFA. Application of ethanol extracts
from ginger or sweet flag improved GLA yield by 30 % or
25 %, respectively. On the other hand, biosynthesis of GLA
was reduced by 70 % when acetone extract from tansy was
employed to the substrate.
Conclusions
naturally prepared cereal based bioproducts enriched
with PUFAs may be used as an inexpensive food and feed
supplement. Thus, the association of selected microorganisms