Starch/cellulose has become the major feedstock for manufacturing biofuels and biochemicals because of their abundance and sustainability. In this study, we presented an artificially designed “starch-mannose-fermentation” biotransformation process through coupling the advantages of in vivo and in vitro metabolic engineering strategies together. Starch was initially converted into mannose via an in vitro metabolic engineering biosystem, and then mannose was fermented by engineered microorganisms for biomanufacturing valuable mannosyl compounds. The in vitro metabolic engineering biosystem based on phosphorylation/dephosphorylation reactions was thermodynamically favorable and the conversion rate reached 81%. The mannose production using whole-cell biocatalysts reached 75.4 g/L in a 30-L reactor, indicating the potential industrial application. Furthermore, the produced mannose in the reactor was directly served as feedstock for the fermentation process to bottom-up produced 19.2 g/L mannosyl-oligosaccharides (MOS) and 7.2 g/L mannosylglycerate (MG) using recombinant Corynebacterium glutamicum strains. Notably, such a mannose fermentation process facilitated the synthesis of MOS, which has not been achieved under glucose fermentation and improved MG production by 2.6-fold than that using the same C-mole of glucose. This approach also allowed access to produce other kinds of mannosyl derivatives from starch.

淀粉/纤维素因其丰富性和可持续性而成为制造生物燃料和生物化学品的主要原料。在这项研究中，我们通过将体内和体外代谢工程策略的优势结合在一起，提出了一种人工设计的“淀粉-甘露糖发酵”生物转化过程。淀粉最初通过体外代谢工程生物系统转化为甘露糖，然后甘露糖通过工程微生物发酵，用于生物制造有价值的甘露糖基化合物。在体外基于磷酸化/去磷酸化反应的代谢工程生物系统在热力学上是有利的，转化率达到81%。使用全细胞生物催化剂在 30 升反应器中生产甘露糖达到 75.4 g/L，表明具有潜在的工业应用。此外，反应器中产生的甘露糖直接作为发酵过程的原料，使用重组谷氨酸棒杆菌自下而上产生 19.2 g/L 甘露糖基低聚糖 (MOS) 和 7.2 g/L 甘露糖基甘油酸酯 (MG)菌株。值得注意的是，这种甘露糖发酵过程促进了 MOS 的合成，这在葡萄糖发酵下是无法实现的，并且与使用相同 C 摩尔葡萄糖的情况相比，MG 产量提高了 2.6 倍。这种方法还允许从淀粉中生产其他种类的甘露糖衍生物。