Optimal poly (3-hydroxybutyrate/3-hydroxyvalerate) biosynthesis by fermentation liquid from primary and waste...

Area of Science:

• Microbiology
• Biotechnology
• Polymer Science

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable polymers with diverse applications.
• Efficient and sustainable production methods for PHAs, such as poly (3-hydroxybutyrate/3-hydroxyvalerate) (PHBV), are crucial.
• Utilizing waste streams as carbon sources for microbial PHA synthesis is an environmentally sound approach.

Purpose of the Study:

• To investigate the biosynthesis of poly (3-hydroxybutyrate/3-hydroxyvalerate) (PHBV) using activated sludge.
• To optimize the carbon source derived from primary sludge (PS) and waste activated sludge (WAS) fermentation liquid for PHBV production.
• To determine the optimal conditions for PHBV synthesis with a high hydroxyvalerate (HV) fraction.

Main Methods:

• Fermentation liquid from PS and WAS was used as the carbon source.
• Acetic to propionic acid ratios were optimized for PHBV synthesis.
• Aerobic feeding and discharge processes were employed for PHBV production.
• Polymerase chain reaction-based 454 pyrosequencing was used for microbial community analysis.

Main Results:

• Optimized fermentation conditions yielded a PHBV content of 65.5% in the sludge.
• The hydroxyvalerate (HV) unit content reached 47.8% (mol-C based).
• A polyhydroxyalkanoates yield of 1.44 g/L was achieved using acclimated sludge.
• Thauera strains were identified as the predominant microbial species.

Conclusions:

• This study presents the first reported optimal PHBV biosynthesis using activated sludge as the microbial source and sludge fermentation liquid as the carbon source.
• The developed method demonstrates efficient PHBV production with a significant HV component.
• The findings highlight the potential of waste activated sludge and primary sludge for sustainable biopolymer production.