# Cold-Adapted Fungi: Goldmine of Biomolecules Applicable in Industry
## 4 Biotechnological Application of Psychrophilic Fungi in Food and Agriculture
### Osmolytes  
Osmoprotectants, also known as compatible solutes, are low-molecular-weight, non-toxic organic osmolytes [49]. Psychrophilic fungi accumulate osmolytes such as polyamines, sugars (e.g., glucose, fructose, ribose, sucrose, trehalose), polyols (e.g., glycerol, sorbitol, mannitol), and amino acids (e.g., alanine, proline) [49; 137]. Many cold-adapted microorganisms contain numerous genes in their genomes responsible for the production and degradation of osmoprotectants and their concentration in cells can reach molar levels. These substances function as specific cryoprotectants, reducing the freezing point of water outside and inside of the cells, thus providing specific protection against freezing, drying, and hyperosmolarity. Additionally, compatible solutes possess the capacity to trap free radicals. However, it is important to note that the amount and type of osmolytes produced depend on the species of the psychrophilic microorganism [100].  
The increase in the production of sugars such as trehalose has been observed in the following species: _Penicillium olsonii_ p14, _Humicola marvini_, _Mrakia blollopsis_, and _Mortierella elongata_. Compared to other sugars, trehalose has been demonstrated to possess remarkable cryoprotective properties against biomolecules and whole cells. Firstly, it has been shown to prevent ice crystallization by disrupting the tetrahedral hydrogen bond network in water molecules. Secondly, it has been observed to form a specific envelope around proteins that slows down water dynamics, thereby protecting these molecules from denaturation and aggregation, while also stabilizing cell membranes at low temperatures [44; 138; 139].  
Polyols, such as mannitol and glycerol, are frequently synthesized by cold-adapted fungi. Glycerol production enables the regulation of turgor pressure within cells and is produced by fungi such as _Geomyces panororum_, _Thelebolus microspos_[140], and _Flammulina velutipes_[141]. Conversely, fungi utilize mannitol for carbon storage, redox balance maintenance, and as an antioxidant [142]. Glycerol is extensively employed in the food industry, with applications as a cryoprotectant and as a precursor for several other substances, including sweeteners. Furthermore, it is one of the most effective humectants. In contrast,mannitol is widely used in the food industry, primarily due to its low metabolic rate and lack of a glycemic index [143]. Therefore, there is a need to identify novel sources of polyols with potential applications in the food industry.  
Osmolytes are already being used on an industrial scale for cryopreservation and stabilization of various biological materials. These compounds will undoubtedly enhance the freshness and stability of frozen food. One consequence of global climate change is an increase in soil salinity and desiccation. It is estimated that major abiotic stresses result in an annual global crop yield loss of between 51% and 82% [144]. The utilization of osmolytes may prove to be an effective strategy for preventing crop loss, offering protection from low temperatures and, in particular, from desiccation and high salinity [145].