Conversion of polyhydroxyalkanoates to methyl crotonate using whole cells

Area of Science:

• Biotechnology
• Polymer Science
• Sustainable Chemistry

Background:

• Polyhydroxyalkanoates (PHA) are biopolyesters with potential for producing biobased chemicals.
• Current PHA isolation methods are complex and expensive, limiting their industrial application.
• Utilizing whole cells containing PHA offers a promising alternative to bypass extensive downstream processing.

Purpose of the Study:

• To investigate the direct conversion of PHA from whole cells into methyl crotonate, a valuable biobased chemical.
• To evaluate the impact of impurities, such as 3-hydroxyvalerate, magnesium salts, and water content, on the conversion efficiency.
• To determine the feasibility of minimizing downstream processing for PHA utilization.

Main Methods:

• Production of PHA-rich whole cells from wastewater, containing 3-hydroxybutyrate and 3-hydroxyvalerate.
• Enzymatic conversion of 3-hydroxybutyrate monomer to methyl crotonate using whole cells.
• Systematic variation of water content (up to 20%), 3-hydroxyvalerate concentration, and magnesium salt presence (with different counter ions).
• Analysis of conversion yields and byproduct formation.

Main Results:

• The presence of 3-hydroxyvalerate and water content up to 20% did not negatively affect the conversion of 3-hydroxybutyrate to methyl crotonate.
• Magnesium ions (Mg2+) influenced the reaction outcome, either enhancing yield or promoting byproduct formation depending on the counter ion.
• Successful conversion of PHA to methyl crotonate was achieved, demonstrating the potential to bypass significant downstream purification steps.

Conclusions:

• Whole-cell conversion of PHA is a viable strategy to produce biobased chemicals, significantly reducing processing costs.
• The process is robust to common impurities found in PHA-rich biomass, such as 3-hydroxyvalerate and moderate water levels.
• Optimization of reaction conditions, particularly concerning the influence of specific magnesium salts, is key for maximizing yield and minimizing byproducts.