## 4 The Behavior of _Saccharomyces cerevisiae_ in Stressors Action
\begin{table}
\begin{tabular}{c c} \hline \hline
**Cell Stress Genes** & **Biological Stress Response** \\ \hline _BSD2_ & involved in metal ion transport (IMP), protein targeting to vacuole (IMP), ubiquitin-dependent protein catabolic process (IMP) \\ \hline _CTT1_ & involved in response to reactive oxygen species (IMP), protection from oxidative damage by hydrogen peroxide \\ \hline _DAK1_ & involved in glycerol to glycerone phosphate metabolic process (IGI), involved in stress adaptation \\ \hline _DDR48_ & involved in DNA repair (IDA, IMP), expression is increased in response to heat-shock stress \\ \hline _GTT1_ & involved in glutathione metabolic process (IDA) and protein glutathione (IMP) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: _Saccharomyces cerevisiae_ common genes with a role in stress response [78; 79]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Method** & **Details** \\ \hline Microbial contamination control & Sanitization operations of fermentation processes, use of antimicrobial products \\ \hline Ensuring optimal physiological conditions & Correct cold storage temperature, optimal \\  & pre-propagation conditions \\ \hline Use of improved yeast strains & Application of genetic and physiological techniques to \\  & optimize stress resistance \\ \hline Ensuring proper yeast nutrition & Micronutrient balance, bioavailability for metal ions \\ \hline Control of fermentation parameters & pH, temperature, agitation, specific density of the medium, \\  & dissolved oxygen \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Ways to reduce stress on yeast cells [2]. In order to adapt to the conditions to which they are exposed, especially to stress, yeast cells go through certain changes at the proteome level [35; 80]. A set of proteins that produce positive effects on _S. cerevisiae_ is represented by Msn2 and Msn4 (Msn 2/4). They are able to stop the mutation of the _SNF1_ gene and regulate some stress responses. Through cycles of phosphorylation and dephosphorylation, proteins are activated to produce certain effects. For example, ethanol tolerance and fermentation improvement in the yeast _S. cerevisiae_ can be influenced after the phosphorylation of specific serine residues of Msn 2/4. Of course, proteins can also act in a less desirable way on _S. cerevisiae_. They can decrease their growth rate by overwriting the binding domain of their DNA [81]. The phosphorylation processes controlling Msn2/4 are represented by low protein kinase A (PKA) activity and low nitrogen and glucose concentrations. Instead, dephosphorylation relies on intense PKA activity and high glucose concentration. In addition to these two, the functions of Msn2/4 are also influenced by the nuclear and cytoplasmic localization of the reactions taking place under the catalysis of the protein kinase Tpk1-3, specific for the cAMP-PKA signaling pathway. In other words, it can be said that this pathway is responsible for the thermotolerance of _S. cerevisiae_ cells, the influence of some of the cellular processes and the accumulation of stress-resistant substances (glycerol, trehalose, and glycogen). Also, both under normal conditions and under cellular stress, the cAMP-PKA pathway can identify and respond to high or low amounts of nitrogen and glucose [64; 82]. In the case of the yeast _S. cerevisiae_, the cAMP-PKA signaling pathways contain elements such as Msn2/4 (transcription activating proteins), Bcy1-2 (regulatory subunit of PKA), Mep2 (ammonium permease/nitrogen sensor) or Gr1l (sensing glucose, activator of adenylate cyclase). In cAMP-PKA signaling, the DNA binding domain of Msn2/4 has the ability to recognize promoter sequences (AG4 and C4T). At high glucose concentrations, Bcy1 is removed from