Optimization of Synthetic Media Composition for <i>Kluyveromyces marxianus</i> Fed-Batch Cultivation

• Main Authors: Konstantins Dubencovs, Janis Liepins, Arturs Suleiko, Anastasija Suleiko, Reinis Vangravs, Jana Kassaliete, Rita Scerbaka, Oskars Grigs
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Fermentation
• Subjects: <i>Kluyveromyces marxianus</i>; 2-phenylethanol; fed-batch; cultivation; bioreactor; model predictive control (MPC)
• Online Access: https://www.mdpi.com/2311-5637/7/2/62

The <i>Kluyveromyces marxianus </i>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 effi-ciency. 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 <em>K. marxianus</em> 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 <em>K. marxianus</em> biomass growth was identified as C:N:P = 1:0.07:0.011. The maximal attained yeast biomass concentration was close to 70 g·L^-1and the 2-PE biosynthesis rate was 0.372 g·L⁻¹·h⁻¹, with a yield of 74% from 2-phenylalanine.