The end-product concentration and productivity are critical issues in economic competition between biotechnological commercials and the chemical engineering industry. The prominent contradiction between high-titer products and the large-scale oxygen demand for aerobic biocatalysis leads to hyperviscosity, mass transport bottleneck in [dynamically changing](javascript:;) polyphase biosystems, and severe foaming problems. In this study, an intensification strategy for the whole-cell catalytic preparation of high-titer xylonic acid by Gluconobacter oxydans in a sealed-compressed oxygen supply bioreactor is propose. Multi-scale control factors are quantitatively studied to determine the biochemical parameter thresholds, and theoretically calculated the optimal production performance based on threshold effect. Finally, 650.8 g/L xylonic acid is obtained with a maximum productivity of 41.7 g/L/h with a catalytic performance of 95.8%, compared with the theoretical calculations. The intensification strategy for the oxygen transfer threshold effect overcome the stubborn obstacles of obligate aerobic catalysis, while providing a sustainable value-added pathway for fermentative lignocellulose.

The end-product concentration and productivity are critical issues in economic competition between biotechnological commercials and the chemical engineering industry. The prominent contradiction between high-titer products and the large-scale oxygen demand for aerobic biocatalysis leads to hyperviscosity, mass transport bottleneck in [dynamically changing](javascript:;) polyphase biosystems, and severe foaming problems. In this study, an intensification strategy for the whole-cell catalytic preparation of high-titer xylonic acid by Gluconobacter oxydans in a sealed-compressed oxygen supply bioreactor is propose. Multi-scale control factors are quantitatively studied to determine the biochemical parameter thresholds, and theoretically calculated the optimal production performance based on threshold effect. Finally, 650.8 g/L xylonic acid is obtained with a maximum productivity of 41.7 g/L/h with a catalytic performance of 95.8%, compared with the theoretical calculations. The intensification strategy for the oxygen transfer threshold effect overcome the stubborn obstacles of obligate aerobic catalysis, while providing a sustainable value-added pathway for fermentative lignocellulose.

Hydroxyl acid has become an important chemical in the field of materials and medicine due to its dual functional modules. Fortunately, Gluconobacter oxydans whole-cell catalysis is on spotlight with promising potential in bio-catalyzing polyhydroxy chemical to produce hydroxyl acids. Therefore, straight-chain primary diols (C2-C6) were investigated as substrates oxidized by G. oxydans. As results, we found a fantastic critical point of methylene-number determining end-products. G. oxydans catalyzes C4 and smaller methylene-number compounds only forming hydroxyl acids, but C5/C6 can be converted to diacids. Furthermore, it was important that we successfully selective and directionality controlled the product of C5/C6 primary diols to hydroxyl acids instead of diacids through the regulation of pH≥5.5. Finally, we successfully produced nearly 102.3 g/L 5‑hydroxyvaleric acid during 48 h with 99.8% yield by sealed-oxygen supply (SOS) biotechnology which is the highest level. These findings have important reference significance for the selective and directionality bioconversion of primary diols into hydroxyl acids and provide a promising path for the industrial development of hydroxyl acids with integrating C2-C6.

Oxygen, as a terminal electron acceptor, is an essential substrate in the aerobic bio-oxidation process, affecting bacterial vitality and bio-oxidation performance. In this study, a new and smart platform biotechnology of sealed-oxygen supply bioreactor (SOS-BR) was developed by improving gas pressure to significantly intensify oxygen transfer rate and resolving the formidable barriers of aerobic catalysis. In virtue of SOS-BR, the bio-productivity was greatly improved for three representative substrates (xylose, furfural, glycerol) bio-oxidation with the whole-cell catalysis of Gluconobacter oxydans. The determination of oxygen transfer coefficient (KLα) established an upgraded theoretical dynamic model for gas pressure intersification biosystem. Additionally, viscosity measurement and combined pressure control strategy explained the inflection point phenomenon of productivity and confirmed the intensify mechanism. The new strategy of significantly intensifying oxygen transfer provided insightful ideas for overcoming the subbon obstacle of obligate aerobic catalysis, and further promoted industrial practicability of bio-oxidation.