Exploring small-scale chemostats to scale up microbial processes: 3-hydroxypropionic acid production in S. cerevisiae

Area of Science:

• Biotechnology
• Microbial Physiology
• Biochemical Engineering

Background:

• Physiological characterization of microorganisms is crucial for bioprocess development.
• Chemostat cultivation allows controlled manipulation of parameters like growth rate for reproducible data.
• This study focuses on a 3-hydroxypropionic acid (3-HP) producing Saccharomyces cerevisiae strain.

Purpose of the Study:

• To characterize the physiology of a 3-HP producing S. cerevisiae strain under varying growth rates and nutrient limitations (C, N, P).
• To optimize 3-HP production using a miniaturized and parallelized chemostat system.
• To validate findings by transferring optimal conditions to larger-scale fed-batch fermentations.

Main Methods:

• Utilized a miniaturized, parallelized chemostat system for physiological characterization.
• Investigated various growth rates controlled by carbon (C), nitrogen (N), and phosphorus (P) limitations.
• Performed subsequent fed-batch cultivations based on optimized parameters from chemostat experiments.

Main Results:

• Identified optimal conditions for 3-HP production, achieving highest yields under phosphate-limiting conditions (21.1 %C-mol and 0.50 g gCDW⁻¹).
• Lowest dilution rate (0.04 h⁻¹) under carbon-limiting conditions yielded 16.6 %C-mol and 0.43 g gCDW⁻¹.
• Transferred optimal conditions to fed-batch fermenters, yielding up to 25.6 %C-mol and 0.50 g gCDW⁻¹ under phosphate limitation.

Conclusions:

• Small-scale chemostat cultures are effective for microbial physiological characterization and process optimization.
• Optimal 3-HP production is achieved at low dilution rates (0.04 h⁻¹) with carbon limitation and under phosphate-limiting conditions.
• The robust nature of growth rate as a process transfer parameter validates the utility of small-scale chemostat systems for bioprocess development.