# Cold-Adapted Fungi: Goldmine of Biomolecules Applicable in Industry
## 4 Biotechnological Application of Psychrophilic Fungi in Food and Agriculture
### Extracellular Polymeric Substances (EPSs)  
A variety of cryoprotective agents are produced by psychrophilic fungi, including extracellular polymeric substances (EPSs). These compounds are known for their high molecular weight (500 to 2000 kDa) [146], and complex, diverse structures. They are primarily composed of carbohydrates, including homo- or heteropolysaccharides, and may also contain proteins, nucleic acids, lipids, phenols, and humic substances [49]. EPSs are produced by various microorganisms to form a specific hydrated gel. They can either be integrated into the cell membrane or secreted into the external environment [49]. A metagenomic analysis of cold-adapted Antarctic and Arctic microorganisms has confirmed the presence of genes involved in EPS production at low temperatures (0-5 \({}^{\circ}\)C), including those below zero [48]. It has been documented that EPSs perform various functions--they are capable of binding water, nutrients, metal ions (mainly in Arctic microorganisms, where metal contamination is significantly higher), and reactive oxygen species (ROS). Moreover, they facilitate surface adhesion, cell aggregation, and biofilm formation, which in turn contributes to better biochemical interactions between microorganisms [44; 48].  
A diverse range of fungal species produce EPSs, with _Cryptococcus laurentii_ AL65 (formerly _Papiliotrema laurentii_) being a notable example. This organism synthesizes a heteropolysaccharide comprising monosaccharides, including glucose, mannose, and xylose, along with proteins [147]. _Phoma herbarum_ CCFEE 5080 has been observed to biosynthesize a glucose homopolymer that is rich in \(\beta\)-1,3 and \(\beta\)-1,6 linkages [148]. _Telebolus_ sp. IITKGP-BT12, which was isolated from soil, has been shown to produce thelabolan, an exopolysaccharideacharide in which a (\(1\to 3;1\to 6\))-linked \(\beta\)-D-glucopyranosyl moiety was identified as the building block [149]. _Rlodotorula mucilaginous_ sp. GUMS16 produces a biopolymer composed of highly branched \(\beta\)-D-glucan with glucose and mannose residues. These examples represent only a fraction of the total number of producers of these industrially relevant bioactive molecules [150]. In several strains, EPS production has been observed, but the structure has yet to be characterized.  
One of the more interesting properties of EPSs is their cryoprotective function. The study by [PERSON] et al. (2017) elucidated that exopolysaccharides exhibit functionalities analogous to antifreeze proteins (AFPs) [151]. Their inhibitory effect on ice recrystallization was found to be comparable to that of synthetic polymer antifreeze glycoproteins, which mimic the activity of AFPs. EPSs have been proven to play a pivotal role in the prevention of ice crystal formation by disrupting its structure and increasing pore density [152; 153].  
The cryoprotective properties of exopolysaccharides produced by psychrophilic fungi may be applicable in the preservation of foods during freezing, thereby maintaining their nutritional value and extending their shelf life. Furthermore, some of these compounds have been observed to exhibit emulsifying and stabilizing activity. A review of the physicochemical properties of EPS indicates that their high molecular weight, polyelectrolyte nature, protein content, and presence of hydrophobic groups may contribute to enhanced surface activity and steric stability during the emulsification process. Consequently, these substances can readily supersede the synthetic emulsifying agents currently employed in the food industry [5; 154]. Additionally, exopolysaccharides can be used as thickening and gelling agents. Their antioxidant activity also represents a significant source of added value for these compounds [154].  
Despite the encouraging physical properties of psychrophilic EPSs, studies examining their functional and biological activities remain limited compared to those conducted on polysaccharides derived from plants, marine algae, neutrophils, and mesophilic microorganisms [154].