# Cold-Adapted Fungi: Goldmine of Biomolecules Applicable in Industry
## 4 Biotechnological Application of Psychrophilic Fungi in Food and Agriculture
### Polyunsaturated Fatty Acids (PUFAs)  
As a consequence of evolutionary processes, psychrophiles have likely undergone specific modifications in the fatty acid composition of the phospholipid bilayer of their cell membranes, thereby rendering them more fluid. One such modification is the reduction in fatty acid (FA) saturation and the shortening of FA chain lengths [113]. Besides FAs, sterols play a crucial structural and regulatory role in eukaryotic cell membranes, influencing their fluidity. Sterols insert themselves among the FA chains, typically stabilizing and reinforcing the membrane lipid bilayer [114]. They can condense the membrane if the lipids are in a liquid crystalline state or liquefy it if they are in a gel state [115]. In yeasts _Mrakia blollopsis, Leucosporidium creatinitorum, Vishniacozyma victoriae_, and _Goffeauzyma gastrica_, ergosterol is the main sterol [102]. These strains demonstrated ergosterol production of 6.91 mg, 4.03 mg, 1.5 mg, and 2.13 mg per gram of dry weight, respectively. Ergosterol is a precursor of vitamin D2 and therefore represents a significant potential as a food additive and a dietary supplement [102; 116].  
Polyunsaturated fatty acids (PUFAs) like omega-3 (\(\alpha\)-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid) and omega-6 (linoleic acid, arachidonic acid) demonstrate health-promoting properties and are used in medicine, pharmaceutics, cosmetics, nutrition, food technology, and agriculture. In humans, they are responsible for the regulation of the cardiovascular system and the immune system, including the control of inflammation, as well as for the development and normal function of the brain and central nervous system. It is well established that providing a balanced intake of omega-3 and omega-6 acids is fundamental to a healthy diet. Furthermore, long-chain PUFAs (particularly DHA and ARA) are strongly recommended for infants [117; 118].  
Presently, the principal source of polyunsaturated fatty acids (PUFAs) and long-chain PUFAs is fish oil derived from species belonging to the families _Scombridae_, _Salmonidae_, and _Clupeidae_. Fish oil possesses a distinctive taste and aroma and may cause allergic reactions [119]. Furthermore, the production of fish oil is subject to fluctuations in global fish stocks and the prevalence of environmental pollution. The PUFAs derived from non-vegetarian sources are not suitable for consumption by the growing population of vegetarians. These factors have led to the pursuit of alternative sources of these acids.  
The primary focus has been on oleaginous microorganisms, including psychrophilic and psychotrophic fungi, which have been identified as a rich source of these compounds. Among the yeast species capable of withstanding low temperatures are _Lodderomyces elongisporus_ and _Rhodotorula mucilaginous_[120]. Both strains accumulate 48-54% of lipids in a High-Glucose Basal Defatted Medium with a C:N ratio of 8:1 at 15 \({}^{\circ}\)C [120]. Another yeast producer of PUFAs is presented in Table 2. The literature also describes fungal producers such as _Thelebolus micros spores_[13] and _Mortierella alipina_.  
Since 2001, the psychrophilic fungus _Mortierella alipina_ has been known to produce arachidonic (ARA) and docosahexaenoicenoic (DHA) acids, which are used in food production, particularly in infant diets [119]. In this instance, the substitution of fish oil with microbial sources increases the safety profile, as toxic substances such as dioxins and heavy metals, which may bioaccumulate in fish, are no longer present. Furthermore, PUFAs derived from cold-forming microorganisms can be employed as additives in animal feeds or aquarium foods [121; 122].