Firstly, the overall sugar concentration in OPEFB was adjusted to 45 g/L and 9 g/L tryptone was supplemented to maintain C/N ratio of 15:3. As can be seen in Fig. 4, the maximal CDW (15.93 ± 0.76 g/L), PHB content (58.5 ± 1.3%), and PHB production (9.32 ± 0.70 g/L) were observed at 48 h. The corresponding residual glucose and xylose dropped to 1.2 g/L and 8.9 g/L, respectively.