The ejector-loop fermenter: Description and performance of the apparatus.

Area of Science:

• Biotechnology
• Chemical Engineering
• Microbial Fermentation

Background:

• Traditional fermentation units often rely on expensive air compressors for aeration.
• There is a need for energy-efficient and effective aeration systems in industrial fermentation.

Purpose of the Study:

• To design and construct a novel ejector-loop fermenter (ELF) for efficient aeration.
• To evaluate the performance of the ELF in whey fermentation using Kluyveromyces fragilis.
• To compare the ELF's oxygen transfer capability and power consumption with conventional fermenters.

Main Methods:

• A novel ejector-loop fermenter (ELF) was designed and constructed, incorporating a tower fermenter, pump, heat exchanger, and gas-liquid ejector.
• Aeration was achieved by recirculating the fermentation medium through nozzle devices.
• Whey fermentation experiments were conducted comparing the ELF with a conventional stirred fermenter.

Main Results:

• The ELF successfully achieved aeration without affecting microbial growth, despite shear stresses in the ejector.
• Oxygen transfer capability ranged from 1 to 2.5 kg O2 kW−1h−1 within the tested power consumption range.
• Optimizing the aeration device design, specifically nozzle size, significantly impacts power consumption, with a 4-mm nozzle showing ~40% less power usage than a 6-mm nozzle at constant oxygen transfer.

Conclusions:

• The ejector-loop fermenter (ELF) is a viable and potentially energy-saving alternative for microbial fermentation.
• Further optimization of the aeration device in the ELF can lead to substantial improvements in energy efficiency.
• The ELF design avoids the need for expensive air compressors, offering a cost-effective aeration solution.