摘要：Phosphorus recycling is essential for the sustainable future of humanity. Phosphite (Pt), a salt of phosphorous acid (H 3 PO 3 ), is a waste product of the chemical and automotive industries. Pt has to be oxidized to phosphate (Pi) prior to phosphorus recycling. Pt dehydrogenase (PtxD), catalyzing oxidation of Pt to Pi with concomitant reduction of NAD + to NADH, could have a number of applications in the efficient utiliza- tion of Pt waste. The originally isolated PtxD, however, showed both thermosensitivity and mostly insoluble expression in an Escherichia coli recombinant, limiting the practical application of this enzyme. To overcome this problem, we obtained a stable and solubly expressed PtxD from a thermotolerant Pt-oxidizing bacterium. Here we describe three emerging applications of PtxD in (i) an NADH regeneration system, (ii) a dominant selection system for recombinant microorganisms, and (iii) Pt fertilization in plants. Firstly, an NADH regeneration system is necessary for the production of industrially important chemicals by oxidoreductive enzymes. Stable PtxD with Pt as a reducing reagent could be used practically as an NADH regeneration system. We demonstrated production of a chiral compound using a PtxD-driven NADH regeneration system. Secondly, selective cultivation of microorganisms is important to the production of medical and chemical compounds and renewable biofuels. Transfection with ptxD (recombinant PtxD trait) allows selective growth of microorganisms on a medium containing Pt as its sole phosphorus source. Pt could be used as an alternative to antibiotics in large-scale cultivation of ptxD-recombinant microorganisms. Finally, direct utilization of Pt as a fertilizer would be the most cost-effective method for the recycling of Pt waste. Pi, however, is the only chemical form of phosphorus that can be assimilated by plants. We and another group demonstrated that ptxD-recombinant plants can directly utilize Pt fertilizer. These new environmental biotechnologies could contribute to efficient utilization of Pt waste.
