Engineering Gluconobacter oxydans for Efficient production of 3,4-dihydroxybutunate or 1,2,4-butanetriol from D-xylose

Abstract

1,2,4-Butanetriol and 3,4-dihydroxybutunate are two important C4-chemicals with versatile applications. Although microbial production of BT and 3,4-DHBA was developed, the current bioprocesses suffer from low titers and yields. Here, Gluconobacter oxydans was engineered as a potential microbial cell factory for BT and 3,4-DHBA production from D-xylose by partially recruiting dehydratase Yagf and decarboxylase ppMdlc. Then, a redox pressure control strategy was employed to direct carbon flux into BT or 3,4-DHBA pathway. Three native reductases and two dehydrogenases toward the intermediate 3,4-dihydroxybutunal were identified for BT or 3,4-DHBA production. Overexpression of reductase Gox0313 enhanced BT production to 5.31 g/L and eliminated the formation of byproduct 3,4-DHBA; meanwhile, overexpression of dehydrogenase Gox0499 decreased the accumulation of BT and significantly promoted the titer of 3,4-DHBA to 5.23 g/L. Finally, the resultant strain G. oxydans/tGox0313-tppMdlc-tYagf and G. oxydans/tGox0499-tppMdlc-tYagf also successfully produced 4.83 g/L BT and 4.64 g/L 3,4-DHBA using D-xylose in distillation stillage of bio-ethanol production, respectively. To our best knowledge, this was the first report of 3,4-DHBA production directly from lignocellulosic feedstocks. These results demonstrated the potential to engineer G. oxydans to efficiently produce BT and 3,4-DHBA from the renewable lignocellulosic feedstocks.