Biological phosphite oxidation and its application to phosphorus recycling

Abstract

Several chemical industrial processes produce phosphite (Pt) as a by-product. This Pt waste should be recycled and reused as an alternative phosphorus (P) source to reduce the demand for nonrenewable phosphate rock reserves. Nearly all organisms require inorganic phosphate (Pi) or its esters as their P source. Therefore, Pt has been considered a biologically inert P compound, hampering the development of biotechnologies that utilize the Pt waste. During the last decade, the molecular mechanisms involved in the metabolism of inorganic reduced P compounds, including Pt, have been elucidated. Pt dehydrogenase (PtxD) catalyzes the oxidation of Pt to Pi, with a concomitant reduction of NAD + to NADH, and thus is a promising biocatalyst for developing Pt-based applications. The initial discovery of PtxD, followed by the finding and development of PtxD enzymes with high catalytic activity and thermostability, facilitated the development of several unique biotechnological applications. These applications include (i) a dominant selective cultivation system for microorganisms and plants, (ii) a biological containment strategy for the safe use of genetically modified organisms, and (iii) a cofactor regeneration system for efficient production of chiral compounds by dehydrogenases. This section describes the emerging biotechnology applications that should contribute to the utilization of Pt as a valuable chemical.