Optimization of Synthetic Media Composition for Kluyveromyces marxianus Fed-Batch Cultivation

The Kluyveromyces marxianus yeast recently has gained considerable attention due to its applicability in high-value-added product manufacturing. In order to intensify the biosynthesis rate of a target product, reaching high biomass concentrations in the reaction medium is mandatory. Fed-batch processes are an attractive and efficient way how to achieve high cell densities. However, depending on the physiology of the particular microbial strain, an optimal media composition should be used to avoid by-product synthesis and, subsequently, a decrease in overall process efficiency. Thus, the aim of the present study was to optimise the synthetic growth medium and feeding solution compositions (in terms of carbon, nitrogen, phosphorous, magnesium, and calcium concentrations) for high cell density K. marxianus fed-batch cultivations. Additionally, the biomass yields from the vitamin mixture and other macro/microelements were identified. A model predictive control algorithm was successfully applied for a fed-batch cultivation control. Biomass growth and substrate consumption kinetics were compared with the mathematical model predictions. Finally, 2-phenylethanol biosynthesis was induced and its productivity was estimated. The determined optimal macronutrient ratio for K. marxianus biomass growth was identified as C:N:P = 1:0.07:0.011. The maximal attained yeast biomass concentration was close to 70 g center dot L-1 and the 2-PE biosynthesis rate was 0.372 g center dot L-1 center dot h(-1), with a yield of 74% from 2-phenylalanine.

Automated summary

This study successfully achieved high cell density K. marxianus fed-batch cultivations by optimizing synthetic growth medium and feeding solution compositions. The maximal attained yeast biomass concentration was close to 70 g/L, with a 2-PE biosynthesis rate of 0.372 g/L/h and a yield of 74%.