Microfluidic artificial photosynthetic system for continuous NADH regeneration and l-glutamate synthesis

Artificial photosynthesis (APS) is an effective way to convert solar energy into chemical energy by simulating the natural photosynthesis system. Currently, APS plays an important role in the regeneration of coenzymes and synthesis of organic matter. Nevertheless, the photocatalytic materials and oxidoreductases used in most bulk reactors are simply distributed in the reaction solution, which results in problems such as poor stability, high price and they cannot be reused. Moreover, the photocatalytic system also has a certain influence on the catalytic activity of oxidoreductase. In this work, we report an efficient and stable microfluidic artificial photosynthetic system for reduced nicotinamide adenine dinucleotide (NADH) regeneration and l-glutamate synthesis under visible light. We fabricate glass capillary and polydimethylsiloxane (PDMS) microfluidic reactors, followed by immobilization of few-layer g-C3N4 and glutamate dehydrogenase in light and dark reactions zones, respectively. The system possesses advantages over the traditional method in terms of its high efficiency, low cost, and sustainability. The experimental results show that the NADH regeneration rate of the system reached 56.03%, the maximum production rate of l-glutamate was 98.3%, and the reaction conversion rate of immobilized glutamate dehydrogenase still reaches 53.2% after ten times of reuse. All these results prove that our system is applicable for synthesizing high value-added compounds by simulating the natural photosynthesis system, which may be a new feasible scheme to alleviate the energy and food crisis.