Selective oxidation of trimethylolpropane to 2,2-bis(hydroxymethyl)butyric acid using growing cells of Corynebacterium sp. ATCC 21245

•Conversion of polyols to hydroxycarboxylic acid by whole cells biotransformation.•Selective oxidation of trimethylolpropane (TMP) using Corynebacterium sp.•Enhancement of oxidation in presence of co-substrates.•pH 8 and 1 v/v/m airflow are optimal conditions for the oxidation process.•Product recovery using ion exchange resin.

Multifunctional chemicals including hydroxycarboxylic acids are gaining increasing interest due to their growing applications in the polymer industry. One approach for their production is a biological selective oxidation of polyols, which is difficult to achieve by conventional chemical catalysis. In the present study, trimethylolpropane (TMP), a trihydric alcohol, was subjected to selective oxidation using growing cells of Corynebacterium sp. ATCC 21245 as a biocatalyst and yielding the dihydroxy-monocarboxylic acid, 2,2-bis(hydroxymethyl)butyric acid (BHMB). The study revealed that co-substrates are crucial for this reaction. Among the different evaluated co-substrates, a mixture of glucose, xylose and acetate at a ratio of 5:5:2 was found optimum. The optimal conditions for biotransformation were pH 8, 1 v/v/m airflow and 500 rpm stirring speed. In batch mode of operation, 70.6% of 5 g/l TMP was converted to BHMB in 10 days. For recovery of the product the adsorption pattern of BHMB to the anion exchange resin, Ambersep® 900 (OH−), was investigated in batch and column experiments giving maximum static and dynamic binding capacities of 135 and 144 mg/g resin, respectively. BHMB was separated with 89.7% of recovery yield from the fermentation broth. The approach is applicable for selective oxidation of other highly branched polyols by biotransformation.