Single Cell Protein Production From Ethanol: Model-Based Bioreactor Operation at Industrial Scale

Area of Science:

• Biotechnology
• Biochemical Engineering
• Industrial Microbiology

Background:

• Ethanol, a fermentation feedstock, can be synthesized from CO2 via electrocatalysis, coproducing oxygen.
• Single Cell Protein (SCP) production offers a sustainable protein source.

Purpose of the Study:

• To assess the industrial-scale feasibility of ethanol fermentation for SCP production using pure oxygen.
• To model microbial kinetics, gas-liquid transfer, and operational constraints.

Main Methods:

• A modeling approach was employed to simulate a 600 m³ bubble column fermenter operating in continuous mode.
• Key factors analyzed include microbial kinetics, oxygen transfer rates, and dissolved CO2 concentrations.
• Potential operational constraints and heat production were evaluated.

Main Results:

• Technical feasibility for producing up to 58 kt/y of SCP was demonstrated, primarily due to a high oxygen transfer rate (1.1 mol/(kg h)).
• A microbial biomass concentration of 114 g/kg and an ethanol yield of 0.61 gx/gethanol (>95%) were estimated.
• Significant amounts of unconsumed oxygen, high dissolved CO2, and substantial heat production were identified as potential limitations.

Conclusions:

• The high oxygen transfer capacity for SCP production appears technically feasible but requires experimental validation.
• The developed model can analyze alternative substrates and optimize carbon feedstock selection for SCP production.