Exploiting Mixed Waste Office Paper Containing Lignocellulosic Fibers for Alternatively Producing High-Value Succinic Acid by Metabolically Engineered Escherichia coli KJ122.

Succinic acid is applied in many chemical industries in which it can be produced through microbial fermentation using lignocellulosic biomasses. Mixed-waste office paper (MWOP) containing lignocellulosic fibers is enormously generated globally. MWOP is recycled into toilet paper and cardboard, but the recovery process is costly. The reuse of MWOP to alternatively produce succinic acid is highly attractive. In this study, pretreatment of MWOPs with 1% (v/v) H(2)SO(4) at 121 °C for 20 min was found to be optimal. The optimal conditions for the enzymatic hydrolysis of H(2)SO(4)-pretreated MWOP (AP-MWOP) were at 50 °C, with cellulase loading at 80 PCU/g AP-MWOP. This resulted in the highest glucose (22.46 ± 0.15 g/L) and xylose (5.11 ± 0.32 g/L). Succinic acid production via separate hydrolysis and fermentation (SHF) by Escherichia coli KJ122 reached 28.19 ± 0.98 g/L (productivity of 1.17 ± 0.04 g/L/h). For simultaneous saccharification and fermentation (SSF), succinic acid was produced at 24.58 ± 2.32 g/L (productivity of 0.82 ± 0.07 g/L/h). Finally, succinic acid at 51.38 ± 4.05 g/L with yield and productivity of 0.75 ± 0.05 g/g and 1.07 ± 0.08 g/L/h was achieved via fed-batch pre-saccharified SSF. This study not only offers means to reuse MWOP for producing succinic acid but also provides insights for exploiting other wastes to high-value succinic acid, supporting environmental sustainability and zero-waste society.