## 1 Introduction  
In the brewing industry, the most frequently used species of yeast are _Saccharomyces cerevisiae_ and _S. pastorianus_[1]. In industrial breweries, it is possible to ensure the appropriate quality of yeast biomass thanks to the laboratory facilities. In the case of smaller breweries, the number of propagation stations is constantly growing. After propagation, brewer's yeast can be used for subsequent fermentation cycles [2]. Craft breweries that do not have propagation stations use dried yeast. Dried yeast has similar characteristics to fresh yeast in terms of aroma compound formation, fermentation rate and attenuation [3]. Yeast can be dried in several ways, including spray drying or drying with the use of a fluidized bed. However, this drying process is very stressful for the cells and many changes can take place as a result of this operation. These changes contribute to a reduction in the activity of microorganisms [4, 5]. Therefore, in order to obtain yeast with high activity and viability, it is often necessary to use substances that protect these microorganisms. These substances can be divided into two groups: stabilizing agents (trehalose, mannitol and xylose) and substances reducing water activity (glycerin, maltitol and xylitol) [6]. Spray drying, on the other hand, requires a large amount of energy of at least 2500 Jg\({}^{-1}\) for water evaporation to occur [7; 8]. During drying, water is quickly drained through the cell membrane, causing the cytoskeleton to collapse. This condition can adversely affect the physiology of yeast cells by altering the structure and function of the vacuoles, and the integrity and functionality of the membranes of nuclei and cells [9]. Spray drying is advantageous in producing a free flowing material with a controlled particle size range at a rapid drying rate [10]. It has been shown that the rehydration process applied to dried yeast has a significant impact on the viability of yeast cells, which, in turn, has a direct impact on the quality of the final fermentation [8]. The entire process is aimed at restoring the properties of dry yeast comparable to that before treatment via contact with water. Previous reports have examined the influence of water quality on rehydration. [PERSON] et al. [11] studied the effect of rehydration kinetics and temperature on yeast cell viability. Studies have shown that water activity in the range of 0.117-0.455 should be slowly exceeded during rehydration to maintain cell viability [11]. [PERSON] et al. [8] monitored the effect of rehydration medium temperature on the physico-chemical parameters of lager yeast. [PERSON] and [PERSON] [12] demonstrated that yeast cell survival during rehydration depends, among other things, on the rehydration medium. However, the subject of using plasma-treated water (PTW) for rehydration has not yet been described in the literature. The presented work is an ongoing continuation of research on the possibility of using PTW in the brewing industry [13]. The study employed a device built in 2009 to produce PTW under air atmosphere and nitrogen (N\({}_{2}\)). The device is based on the production of low-temperature, low-pressure glow plasma (LPGP) [14], which is used for the first time for water treatment. The application of LPGP to produce PTW is a promising method that requires further development. The technology is mainly supported by data obtained in plant breeding, animal husbandry, cosmeology, medicine and food technology. [PERSON] et al. [15] treated water with LPGP in the presence of air (PTWAir), proving that the structure of the obtained water depends on the time of exposure (5, 15, 30, 45, 60 and 90 min) to plasma that changes nonlinearly. Other studies have described that PTWAir (plasma treated water under air atmosphere) stimulates various microorganisms [16], and promotes plant growth [17] and the healthy breeding of selected animals [18; 19; 20].