The formation of C-C bonds is crucial in synthetic organic chemistry as it connects smaller subunits into more complex molecules. Sophisticated asymmetric methods and protection of functional groups are required in classical synthesis. Biocatalytic condensation is becoming increasingly interesting as it allows the production of sterically pure molecules without the need for functional group protection. Unnatural aldol additions of phosphoenolpyruvate (PEP) to aliphatic and aromatic aldehydes, catalyzed by PEP-dependent aldolases, are investigated in this study, focusing on DHAPH and KDOH enzymes from a metagenomic library. The aim was to optimize reaction conditions and examine the conversion and enantioselectivity of these enzymes to determine their applicability in C-C bond formation. In the experimental part, 38 enzymes from the metagenomic library were tested with different aldehydes. The best results were achieved with the KDOH enzyme and phenylacetaldehyde, with conversions reaching up to 92,7 %. Carbamate compounds were particularly notable, with conversions exceeding 56,6 %. Optimization of dimethylformamide (DMF) content showed that reducing DMF increases enzyme activities, but its complete removal is undesirable due to the insolubility of aldehydes in water. A DMF content of 5 % compared to 20% led to a significant increase in conversion, up to 44,9 %. Further testing of purified enzymes showed lower conversion rates compared to initial screening, possibly due to the loss of stabilizing factors or partial denaturation of enzymes during purification. Additionally, enantioselectivity could not be clearly determined due to low enzyme activity and the formation of by-products instead of target reaction products. DHAPH and KDOH enzymes have potential for further application in C-C bond formation, but additional research and optimization of reaction conditions are needed to achieve satisfactory results.