Efficient 3-hydroxypropionic acid production by Acetobacter sp. CIP 58.66 through a feeding strategy based on pH...

Area of Science:

• Biotechnology
• Industrial Microbiology
• Biochemical Engineering

Background:

• Acetic acid bacteria (AAB) convert diols to hydroxyacids, with potential for 3-hydroxypropionic acid (3-HP) production from 1,3-propanediol (1,3-PDO).
• Current methods using resting cells at high densities are limited by intermediate 3-hydroxypropanal (3-HPA) accumulation.

Purpose of the Study:

• To develop an alternative, efficient 3-HP production method using growing AAB cells at lower densities.
• To prevent 3-HPA accumulation and optimize 3-HP production via a controlled feeding strategy.

Main Methods:

• Characterization of Acetobacter sp. CIP 58.66 growth and 3-HP production using 1,3-PDO or glycerol.
• Implementation of a sequential bioreactor process: glycerol cultivation followed by continuous 1,3-PDO feeding controlled by pH.
• Testing of different pH set points (5.0, 4.5, 4.0) to leverage AAB's acid tolerance.

Main Results:

• A pH set point of 5.0 yielded high performances: 69.76 g/L 3-HP titer, 2.80 g/L/h mean productivity, and 1.02 mol/mol molar yield.
• Achieved results comparable to genetically modified strains at neutral pH, but with significantly lower cell densities (0.88–2.08 g/L).
• The continuous feeding strategy effectively prevented 3-HPA accumulation.

Conclusions:

• A sequential bioreactor process with controlled 1,3-PDO feeding at pH 5.0 offers a highly efficient method for 3-HP production using AAB.
• This approach overcomes limitations of previous methods, enabling cost-effective production due to lower cell densities and reduced energy needs.
• The strategy is well-suited for industrial scale-up, paving the way for sustainable production of this valuable building-block.