## 3 Biotechnological Preparation of Cereals Enriched with PUFA via Fungal Solid State Fermentation
### Regulation of the SSF Process for the Production of PUFA-Enriched Cereals  
The accumulation and amount of microbial PUFA in fermented cereals depend on the substrate, microorganisms, and cultivation conditions. Solid state fermentation is often carried out with the help of an internal solid support or a matrix (e.g., spent malt grains) that is required for improving the efficiency of respiration and aeration, the elimination of heat formed during the fermentation process, and for the reduction of substrate particle agglomeration [33]. Adequate oxygen availability is also necessary for high-activity enzymes that transform carbon to PUFA. The appropriate moistening of a substrate is a significant factor for optimal fungal growth and the evaporative cooling of the fermentation mass. Water serves as a solvent for nutrients and is also necessary for the intracellular transport of mass and for the physical protection against turgor forces. In addition, proper water activity of the cereal substrate prevents the growth of undesired microorganisms and considerably alters both the formation of air in the mycelium and the yield of PUFA [24; 33]. Heterogeneity of the cereal substrate and the need for a well-balanced utilization of nutrients from the cereal substrate is a basic problem of fungal SSF. To increase carbon source availability for microorganisms, either partial hydrolysis (chemical, enzymatic) of the cereal substrate or gradual elevation of the carbon/nitrogen ratio using appropriate carbon source supplementation of the cereal substrate could be performed. Nutritional regulation of SSF also includes the supplementation of cereals with various ions (e.g., Ca\({}^{2+}\), Fe\({}^{2+}\), Mg\({}^{2+}\), Zn\({}^{2+}\), Mn\({}^{2+}\)) and activators or inhibitors (e.g., isolated from plants) that modify enzyme activity involved in the carbon flow to the target PUFA [29]. Depending on the substrate and cultivation conditions, several fermented cereal products enriched with PUFA have been prepared. Under optimal conditions, the final _Thammidium elegans_-fermented cereals yielded up to 20 g of GLA/kg of FP [35]. _Mortierella isabellina_ sufficiently enriched barley with 18 g of GLA/kg of FP [35]. Supplementation of PUFA precursors in the form of extracellular plant oils was also applied for enrichment of cereals with GLA. Cultivation of _Cumningham elegans_ on a mixture of barley/spent malt grains/peanut oil led to the production of 14.2 g of GLA/kg of product [36]. Growth of _Mucor circinelloides_ on a mixture of rye bran/spent malt grains/sunflower oil yielded up to 24.2 g of GLA/kg of FP [1]. The fungal strain _Mortierella alipina_ was also described to accumulate 32 g of AA/kg of bioproduct during utilization of a mixture of corn meal and animal fat [32]. Similarly, _Umbelopsis isabellina_ growing on a mixture of corn meal and animal fat formed both 6.4 mg of GLA/g of FP and 45 ug of \(\beta\)-carotene/g of FP [37]. In addition, the growth of \begin{table}
\begin{tabular}{c c c c} \hline
**Strain** & **Cereal Substrate** & **PUFA** & **Yield [g/kg FP]** \\ \hline _Thammidium elegans_ & \begin{tabular}{c} spelt flakes/SMG \\ wheat bran/SMG/sunflower oil \\ wheat bran/SMG/sunflower oil/plant extract \\ crushed corn \\ \end{tabular} & GLA & 7.2 \\ \hline _Mortierella isabellina_ & \begin{tabular}{c} barley \\ barley \\ barley/SMG/peanut oil \\ \end{tabular} & GLA & 10.0 \\ \hline _Mucor circinelloides_ & \
\begin{tabular}{c} rye bran/SMG/sunflower oil \\ \end{tabular} & GLA & 24.2 \\ \hline _Mortierella alipina_ &
\begin{tabular}{c} wheat bran/SMG \\ dehulled millet \\ oat bran \\ crushed sesame seeds \\ peeled barley/SMG/linseed oil \\ \end{tabular} & AA & 42.3 \\ \hline GLA—\(\gamma\)-linolenic acid, DGLA—dihomo-\(\gamma\)-linolenic acid, AA—arachidonic acid, EPA—eicosapentaenoic acid, FP—fermented product, SMG—spent malt grains, PUFA—polyunsaturated fatty acids. \\ \end{tabular}
\end{table}