A new continuous feeding mode was developed to optimize the polyhydroxyalkanoates (PHAs) accumulation
step in the three-stage PHAs production process by mixed microbial cultures (MMCs) using mixed
volatile fatty acids (VFAs) as substrate. The continuous feeding assays under low biomass loading rate
(BLR) (in the range of 3.5–5.5 Cmol VFA/Cmol X/d) can be directly fed with feedstock with pH from 5.0
to 10.0 without any pH regulation. The maximum intracellular PHA content of 70.4% and system PHA
yield (Ysys
PHA/S) of 0.81 Cmol PHA/Cmol VFA were achieved under the continuous feeding mode at BLR of
3.86 Cmol VFA/Cmol X/d when directly fed with substrate at pH 5. These values were higher than those
under the pulse wise feeding mode with the same substrate and active biomass concentration. The results
indicated that a self-balanced pH state was formed in the continuous feeding system. Further studies on
the reaction pH and kinetics of the MMCs in the continuous feeding reactor were conducted to understand
the pH variation mechanism and accumulation process. The optimal BLR to get high PHA content
and Ysys
PHA/S was 3.5–5.5 Cmol VFA/Cmol X/d.