Increasing polyhydroxyalkanoate (PHA) yields from Cupriavidus necator by using filtered digestate liquors

Area of Science:

• Biotechnology
• Environmental Microbiology
• Polymer Science

Background:

• Digestate liquor, a byproduct of anaerobic digestion, presents an underutilized resource.
• Polyhydroxyalkanoates (PHAs) are biodegradable polymers with diverse applications.
• Valorizing digestate for bioproduction offers a sustainable approach to waste management.

Purpose of the Study:

• To evaluate micro-filtered digestate liquors as a cost-effective culture medium for PHA production.
• To compare PHA yields using digestate media versus conventional media.
• To identify key nutrients in digestate influencing PHA synthesis by Cupriavidus necator.

Main Methods:

• Micro-filtration (0.22 μm) of digestate liquors from food waste and wheat feed.
• Cultivation of Cupriavidus necator using digestate media and conventional media.
• Quantification of PHA accumulation, cell dry weight, and yield based on volatile fatty acids (VFAs).
• Analysis of nutrient composition in initial and residual media.

Main Results:

• A mixture of food waste and wheat feed digestate liquors yielded a maximum PHA accumulation of 12.29 g/l.
• PHA constituted 90% of the cell dry weight under optimal digestate conditions.
• A yield of 0.48 g PHA/g VFA consumed was achieved, the highest reported for C. necator.
• Essential nutrients for growth included ammonia, potassium, magnesium, sulfate, and phosphate.

Conclusions:

• Digestate liquor is a viable and effective complex medium for PHA production.
• Specific micronutrients like copper, iron, and nickel may be crucial for PHA accumulation.
• This method offers a novel pathway for waste valorization and sustainable biopolymer production.