Figure 5(a) indicates light saturation at around 6000 Ix. Figure 5(b) shows that the temperature must be kept at 25-35~ These parameters should be considered when designing the photobioreactor. As shown in Figure 2, acidogenesis of wastewater is expected in the material recovery system of photosynthetic bacteria. The composition of organic acids, which is related to the performance of acidogenesis, influenced the growth of R. sphaeroides, as shown in Figure 5(c). This result indicates that acetate (n=l), propionate (n=2) and 266 (mgC/L) 200 150 ~tate (so 100 0 0 [e carbon soul 50 ce) nrnFpiTi sugar IO0 time(hr) PHB content (mgC/mgC) 1 150 biomass concentration (mgC/L) -200 0.8 0.6 / 0.4 " 0.2 ~ff~ 0 -0 blomass con( 0 entration content 0 50 100 time(hr) - 150 -100 -50 -0 150 Figure 6. Growth of Rhodobacter sphaeroides and variation of their cell composition and PHB content. Table 1. PHB content of Rhodobacter sphaeroides grown on various carbon source carbon feed maximum source concentration PHB content (mgC/L) (mgC/mgC) acetate 200 39 acetate 400 52 propionate 200 0 n-butyrate 200 9 acetate 100 + propionate + 100 + n-butyrate + 100 21 glucose 200 267 components (PHB, protein and sugar) and PHB content are shown in this figure