Polyhydroxyalkanoates (PHA) production by halophilic mixed microbial cultures (MMCs) draw a lot of attention because of great advantages

such as free sterilization

easily extraction and high production. In this study

halophilic MMC was used to investigate the effect of pH on PHA production in the mixed VFAs fermentation process. The results indicated that there was no significant influence on PHA production in the pH range of 6.5-8.2. PHA production rate and substrate utilization rate would be inhibited in lower or higher pH conditions. PHA yield was influenced by pH in the systems

but different influencing mechanism existed in acidic condition and alkaline condition. Alkaline environment led to higher dissociation degree of VFAs. Then more energy needed as substrates being absorbed

which further led to the decrease of VFAs absorption rate. This affect was obvious when pH raised to 9.2. Molecular-state VFAs changed intracellular pH in the acidic condition. Then

the lower activity of related enzymes and protein resulted in slower substrate utilization. Energy consumption of substrate utilization and microbial metabolism reduced when pH=5.2

resulting in the decrease of intracellular PHA degradation and the increase of PHA yield. The pH value had little influence on PHA component. And HV accounted for 34.9%-38.3% of PHA weight when the initial pH between 5.2 and 10.2. This study would be a guide for PHA production using mixed VFAs as carbon source by halophilic MMCs.