## 3 Discussion
[PERSON] and [PERSON] [39] described a method for increasing cell density and improving process efficiency by supporting the aerobic growth of eukaryotic microorganisms in submerged fermentation bioreactors. [PERSON] et al. [29] also indicated the beneficial effect of oxygen on the growth of _Y. lipolytica_. The concentration of 30% oxygen in the medium was favorable for the growth of the yeast, which reached the stationary phase earlier compared to the other conditions used. The cultures at the initial oxygen ratio of 20% and 40% later reached the stationary phase similar to the results of the present study. The positive effect of oxygen on the production of _Y. lipolytica_ biomass is also confirmed by [PERSON] et al. [40]. The increase inoxygen availability caused by increasing the air pressure to 6 bar had a clear positive effect on yeast metabolism, and the biomass yield increased by 67.8% and 86.4%, respectively, compared to with experiments at atmospheric pressure (control). Other unconventional yeasts, such as _Pichia pastoris_ or _Kluyveromyces marxianus_, were also characterized by higher biomass yields at higher oxygen concentrations in the medium [41]. Taking into account kinetic parameters such as the maximum specific growth rate (\(\mu_{\text{max}}\)), maximum biomass concentration and level of yield of biomass from the substrate (Table 1), relatively high values of these parameters were also achieved for medium based on plasma water treated under nitrogen. Higher values of the yield of yeast biomass growing on the medium enriched with nitrogen (compared to the control) are confirmed in the literature. [PERSON] et al. [42] emphasized that more nitrogen in the medium promotes rapid cell division and generates higher biomass yield. The availability of nitrogen also affects the level of substrate utilization by _Y. lipolytica_, but there are some differences in the way it is assimilated: co-utilization or sequential. It is hypothesized that this phenomenon may be related to carbon and nitrogen source metabolism. At higher nitrogen concentrations (when the C/N ratio is about 20), the cellular machinery of _Y. lipolytica_ is geared toward biomass production. While nitrogen becomes scarce (C/N 40), cells begin to store available carbon in storage molecules such as triacylglycerlecrools and glycogen. The research also confirms that nitrogen availability has a major impact on gene expression in chemostat cultures [43]. It should be remembered that the structure of plasma water and the state of dissolved gases have an impact on living organisms. Water treated with plasma, after passing air or nitrogen through it, acquires different physicochemical properties [15]. In a natural macrosystem, water molecules form a network of hydrogen bonds with structured clusters. Molecules can arrange themselves in various structures, e.g., small four-molecule structures, which can then be grouped into relatively stable octamers [33]. Water molecules also form much larger clusters of water capable of merging and moving through space. These clusters can interconvert between lower and higher structures. The balance between these structures and subsequent changes in the properties of water can be affected by the presence of dissolved gases and components of microbial media and temperature [44; 45]. Gaseous nitrogen and oxygen differ slightly in their molecular properties, but the level of solubility of oxygen in water is twice as high as that of nitrogen [33]. Oxygen molecules interact with the aquatic environment and, according to ab initio molecular dynamics simulations, can form two types of clusters: with and without hydrogen bonding [46]. The second kind of the structural organization of the O\({}_{2}\)-water hydration complex is more preferable energetically. Under plasma treatment, oxygen molecules can be converted to a singlet state and nitrogen molecules can be converted to a triplet excited state. Molecules reside in water clathrates [47].