Sustainable Synthesis of Trimethylolpropane, a Biobased Polyol from Renewable Resources by an Integrated Process of Biotechnology and Chemical Reactions

Trimethylolpropane (TMP) is an important industrial chemical used to produce various value-added chemicals and polymers. In this study, both biobased butyraldehyde and formaldehyde were produced by the incomplete oxidation of bio-1-butanol and biomethanol, respectively, and were then used to produce a biobased TMP. High selective incomplete oxidation of primary alcohol to aldehyde is a challenging process minimizing the corresponding carboxylic acid, a complete oxidation product. Guconobactor oxidans DSM 2343 was found to have high activity and selectivity for the oxidation of butanol to butyraldehyde by whole-cell biotransformation. A pH 5 and greater than 15 g/L of 1-butanol are preferable conditions for butyraldehyde accumulation. In a 1 L bioreactor experiment, 18 g/L of bio-1-butanol was oxidized to 13 g/L of butyraldehyde at an 85% conversion and 93% selectivity. Biomethanol oxidation to formaldehyde was conducted at relatively high concentration using alcohol oxidase from Pichia pastoris. After 48 h of enzymatic reaction, a 52% conversion of 5.5 g/L biomethanol to 2.6 g/L formaldehyde at 100% selectivity without byproduct was achieved. Using the resulting butyraldehyde and formaldehyde, TMP could be produced through aldol and Cannizzaro reactions under basic conditions. The overall process shows a new synthetic route for TMP production that uses renewable resources and integrates both biotechnology and chemical processes.