Regulation of the interaction between the de novo biosynthesis of vitamin B6 and its salvage pathway for efficient production of pyridoxine

Abstract

Vitamin B6, a micronutrient essential for maintaining healthy growth and normal physiological function, is a generic term for six interconvertible substances, of which pyridoxine hydrochloride is the most common commercial form, produced industrially by chemical processes using expensive and/or toxic chemicals. To date, attempts to engineer microorganisms to produce high-level of vitamin B6 have been unsuccessful due to the toxic intermediates and a lack of understanding of the vitamin B6 metabolism regulation. Here, for the first time, we proposed a two-step process for efficient pyridoxine production. A recombinant Escherichia coli was successfully engineered to produce 1406 mg/L of pyridoxal phosphate by interfering with only one or two key enzyme genes expression in the vitamin B6 salvage pathway. Pyridoxal phosphate was then efficiently converted to pyridoxine by another engineered Escherichia coli overexpressing cell membrane-anchored phosphatase YbhA and pyridoxal reductase PdxI, and 2296 mg/L (calculated as pyridoxine hydrochloride) of pyridoxine was achieved with a yield of 0.29 mol/mol (pyridoxine hydrochloride/pyridoxal phosphate) by shake flask cultivation. This achievement marked a significant advance in the biological synthesis of vitamin B6 and demonstrated an efficient vitamin B6 production strategy by reducing interference between the de novo synthesis pathway and the salvage pathway of vitamin B6.