A Downstream Processing Cascade for Separation of Caproic and Caprylic Acid from Maize Silage-Based Fermentation...

Area of Science:

• Biotechnology and Bioengineering
• Sustainable Chemistry
• Separation Science

Background:

• Anaerobic fermentation of biomass offers an alternative to conventional production of caproic acid (C6) and caprylic acid (C8).
• Downstream processing of fermentation broths is challenging due to complex composition and low product concentrations.
• Maize silage is a potential feedstock for producing these valuable carboxylic acids.

Purpose of the Study:

• To demonstrate a proof-of-principle separation cascade for caproic and caprylic acids from maize silage fermentation broth.
• To evaluate the efficiency of different separation techniques in recovering these target products.
• To identify key steps contributing to product loss in the separation process.

Main Methods:

• Fermentation broth clarification using a filter press and ceramic ultrafiltration membrane.
• Liquid-liquid extraction of carboxylic acids using oleyl alcohol.
• Analysis of recovery and loss at each stage of the separation cascade.

Main Results:

• Dry matter content was reduced from 6.8% to 2.3%, yielding a particle-free solution.
• Liquid-liquid extraction achieved 85% efficiency for C6 and 97% for C8.
• Overall recovery was 58% for caproic acid and 66% for caprylic acid.
• Solid-liquid separation using a filter press accounted for a significant product loss of 21% for each acid.

Conclusions:

• The developed separation cascade is effective for recovering caproic and caprylic acids from maize silage fermentation.
• Optimizing solid-liquid separation, potentially with decanter centrifuges or belt filter presses, can minimize product loss and improve overall yield.
• This work provides a foundation for scalable downstream processing of bio-based carboxylic acids.