Ethanol-type fermentation from carbohydrate in high rate acidogenic reactor

Area of Science:

• Biotechnology
• Biochemical Engineering
• Fermentation Technology

Background:

• Continuous flow, high-rate acidogenic reactors are crucial for efficient bioprocessing.
• Molasses is a readily available substrate for fermentation.
• Controlling fermentation pathways is key to maximizing desired product yields.

Purpose of the Study:

• To investigate a new ethanol-type fermentation process.
• To determine optimal operating conditions for maximizing ethanol production.
• To understand the factors influencing propionic acid formation in acidogenic reactors.

Main Methods:

• Utilized a continuous flow, high-rate acidogenic reactor fed with molasses.
• Operated the reactor at controlled pH, organic loading rates, and oxidation-reduction potential (ORP).
• Analyzed fermentation products, including acetic acid, ethanol, and propionic acid, under varying conditions.

Main Results:

• Achieved ethanol-type fermentation with simultaneous acetic acid production.
• Maintained minimal propionic acid yield at pH 4.5, even with high organic loading (80-90 kg COD/m³ d).
• Observed significant propionic acid yield increase when operating pH was raised to 5.5.

Conclusions:

• The study demonstrates a viable method for continuous ethanol-type fermentation using molasses.
• Optimal pH control (around 4.5) is critical for suppressing undesired propionic acid formation.
• Propionic acid production is not solely dependent on high hydrogen partial pressure, but significantly influenced by pH.