For the purposes of increasing the green character in biotransformations for the production of biologically active compounds, the number of studies focused on the possibility of using natural eutectic solvents and enzymes as biocatalysts is growing, which significantly reduces the negative effect of classical chemical synthesis. In this study, the influence of selected environmentally friendly eutectic solvents based on choline chloride and betaine on the activity and changes in the conformation of the enzyme alcohol dehydrogenase and on the stability of the reduced and oxidized form of nicotinamide coenzyme was investigated. The test results showed that the eutectic solvents betaine: ethylene glycol and choline chloride: urea have a stabilizing effect on enzyme activity and on both coenzymes. Since chiral alcohols are the key precursors in the preparation of drugs and fine chemicals, the enantioselective reduction of 2-chloro-1- (3,4-difluoro-phenyl)ethanone catalyzed by oxidoreductive enzymes of the baker's yeast Saccharomyces cerevisiae in natural eutectic solvents betaine:ethylene-glycol with different water contents was performed. Additionally, the eutectic solvent choline-chloride: urea has also been shown as a suitable solvent in previous tests. The biocatalytic reduction reaction in the eutectic solvent betaine: ethylene glycol resulted in higher yields compared to the bioreductions performed in pure water and buffer.