High cell density cultivation of Pseudomonas putida strain HKT554 and its application for optically active sulfoxide production.

Culture conditions with Pseudomonas putida strain HKT554, expressing naphthalene dioxygenase, known as the biocatalyst showing wide substrate specificity, were optimized for high cell density cultivation (HCDC). Culture in a medium TK-B modified from that for HCDC of Escherichia coli with glucose fed-batch and dissolved oxygen stat resulted in a high cell density growth of 114 g dry cell/l at 40 h of cultivation. This system was further applied for S-(+)-methyl phenyl sulfoxide (MPSO) production from methyl phenyl sulfide. Addition of nonpolar organic solvent, such as n-hexadecane, greatly enhanced the MPSO production due to the prevention of substrate evaporation, resulting in a MPSO production up to 39 mM in 30 h with a conversion rate of 95.7 mol%.