Manganese orchestrates a metabolic shift leading to the increased bioconversion of glycerol into α-ketoglutarate.

Abstract

Glycerol is a major by-product of the biodiesel industry and its transformation into value-added products is an ongoing technological challenge. Here we report on the ability of the nutritionally-versatile Pseudomonas fluorescens to synthesize copious amount of α-ketoglutarate (KG) in a glycerol medium supplemented with manganese (Mn). The enhanced production of this keto-acid was mediated by the increased activities of isocitrate dehydrogenase (ICDH)-(NAD)P dependent and aminotransaminases. At stationary phase of growth when the optimal quantity of KG was recorded, these enzymes exhibited maximal activities. Two isoforms of pyruvate carboxylase (PC) that were identified in the Mn-treated cells provided an effective route for the synthesis of oxaloacetate, a metabolite critical in the production of KG. Furthermore, the increased activities of phosphoenol pyruvate carboxylase (PEPC) and pyruvate orthophosphate dikinase (PPDK) ensured the efficacy of this KG-generating metabolic system by supplying pyruvate and ATP from the oxaloacetate synthesized by PC. Mn-exposed whole cells converted 90% of industrial glycerol into KG. This Mn-evoked metabolic network can be optimized into the economic transformation of glycerol into KG.

Keywords

• bioconversion
• glycerol
• α-ketoglutarate
• manganese
• pyruvate carboxylase
• metabolic networks