Micro-oxygen Process Improved Synthesis of PHAs with Undomesticated Excess Sludge

Area of Science:

• Biotechnology
• Environmental Science
• Materials Science

Background:

• Polyhydroxyalkanoates (PHAs) offer a biodegradable alternative to conventional plastics.
• Utilizing excess sludge for PHA synthesis reduces production costs and waste.

Purpose of the Study:

• To investigate the synthesis of PHAs from excess sludge using mixed microbial cultures.
• To evaluate the impact of different aeration volumes and carbon sources on PHA yield.
• To explore the correlation between oxidation-reduction potential (ORP) and PHA production.

Main Methods:

• Excess sludge from different wastewater treatment systems (R1 and R2) was used as mixed microbial cultures.
• Waste fermentation liquid served as the carbon source for PHA synthesis.
• Varying aeration volumes (5-20 L/h) were applied under anaerobic conditions.

Main Results:

• Maximum PHA concentrations of 84.41 mg/g (R1) and 30.8 mg/g (R2) were achieved with volatile fatty acid concentrations of 430-520 mg/L.
• PHA yields increased with aeration, peaking at 10 L/h with 108.6 mg/g (R1) and 58.58 mg/g (R2).
• A decreasing ORP trend was observed during PHA formation, with a "valley point" indicating maximum PHA concentration.

Conclusions:

• Excess sludge can be effectively used for PHA synthesis without prior domestication.
• Aeration volume and ORP are critical parameters for optimizing PHA production.
• ORP can serve as a reliable indicator for monitoring and controlling micro-oxygen PHA synthesis processes.