# Accumulation of Vitamin C in Yeast under Pulsed Electric Field (PEF) Conditions
## 1 Introduction  
Vitamin C is a water-soluble nutrient which cannot be synthesized in the human body due to the loss of the end enzyme (gulonolactone oxidase) on the biosynthesis pathway. It is an important antioxidant circulating in plasma [1]. Vitamin C acts as an electron donor and has an antioxidant effect, protecting important molecules (proteins, DNA) from oxidation. It also plays a role as a cofactor for enzymes involved in hormone synthesis and metabolic energy production [2]. Vitamin C supports the epithelial barrier function against pathogens. It is necessary for the synthesis of collagen proteins and plays an important role in preventing bleeding and repairing wounds [3]. This vitamin promotes iron absorption and collagen formation. It is often added to food as a nutrient (to supplement technological losses) and antioxidant [4]. A varied and balanced diet should ensure the right amount of all nutrients. A diet poor in nutrients leads to deficiencies. Another reason for deficiencies is food processing that causes a loss of, e.g., vitamin C [5]. Common nutrient deficiencies can be prevented or corrected not only by nutritional advice, but also through the use of food enriched (or fortified) with nutrients or bioactive ingredients [6]. Enriching food with vitamin C is a process that challenges food engineers. This vitamin is easily degraded under the influences of light and temperature, and thus loses its healthpromoting properties [7]. To prevent these unfavorable changes, the microencapsulation process is used [8]. Bioaccumulation of vitamin C in the yeast cells of _Saccharomyces cerevisiae_ is one of the encapsulation methods [9], and a pulsed electric field (PEF) can be used to increase the uptake of minerals and vitamins by microorganisms [10,11]. PEF is a method used in food processing to control the microbiological safety and nutritional, sensory, and physicochemical properties of food products that are important from the consumer's viewpoint. It is a simple, non-toxic, and non-thermal method based on the formation of pores under the influence of short pulses of electricity. It is believed that PEF is better than thermal methods of food processing because it does not cause a loss of nutrients; the PEF method maintains the physical and sensory characteristics of food so that the quality of products does not change. PEF causes the formation or growth of membrane pores, i.e., electroporation of the cell membrane, which in turn increases its permeability to small molecules [12]. Electroporation depends on the voltage; the process duration; the number of pulses and their frequency; as well as on the composition of the membrane; the size and shape of the cell; the temperature; and the location of the cell relative to the electric field line [13]. After the action of the electric field, the pores in the membranes are sealed. In this way, the introduced particles or ions are retained in the cell [14]. The innovation of this study is the introduction of vitamin C, which is sensitive to external factors, to cells of yeast _Saccharomyces cerevisiae_ with the use of a pulsed electric field. In the scientific literature, only the results of research on the accumulation of vitamins and minerals by yeasts from media enriched with these components are available [15]. There are reports indicating that the PEF method (even a high-intensity mode) has no significant effect on the content and antioxidant properties of vitamin C [16]. Research was also conducted on the ability of PEF treatment to increase the accumulation of metallic elements in yeast and bacteria cells [10,11,12,17]. The authors obtained the highest accumulation using the following parameters of PEF treatment: electric field strength 3-5 kV/cm, treatment time 5-20 min, pulse width 10-20 us, and pulse frequency 1 Hz, depending on the type of microorganism and the introduced ion. However, there are no reports of the use of a pulsed electric field to increase the bioaccumulation of vitamin C in living yeast cells.