During the second phase of culture,
(P/C)app was first set at 1 mgP/gCODS from 16 to 30 h and then was
progressively decreased to 0.3 mgP/gCODS. Evolutions of PHB, XC
and PHB content similar to those in the previous culture with
WAS_1 were observed although higher final PHB content was
reached. As expected, the increase of P-limitation to (P/C)app of
0.3 mgP/gCODS resulted in an increase in PHB production and a
slowdown of XC division, the latter being almost nil at the end of
the culture. However, transient AA accumulation was observed
which led to momentary interruption of the P and C feeds. In consequence,
variations of (P/C)cons of about 0.2 mgP/gCODS occurred
which potentially increased the P-limitation level. Hence, it can
be concluded that too harsh a P limitation leads to carbon overflow
and AA accumulation in the supernatant. For WAS_1b, the overall
PHB production yield (RPHB/S), the final PHB content and the maximum
specific PHA storage rate were 0.24 gCODPHB/gCODS (0.21
CmolPHB/CmolS), 67% (gPHB/gVSS) and 0.08 gCODPHB/gCODXc.h
(0.072 CmolPHB/CmolXc.h) respectively (Table 1). A significant
decrease was observed in the PHB yield in comparison to that
obtained for WAS_1a. Too strong P limitation seemed to increase
the maintenance requirements, possibly caused by P intracellular
reorganization (