N-Oxygenation of amino compounds using immobilized and stressed Streptomyces griseus whole cells as biocatalysts

Abstract

Nitro compounds are widely used as building blocks in many industrial syntheses, and are a key component of therapeutic drugs, pesticides and explosives. Due to the harsh environmental conditions associated with their traditional preparation, the development of biocatalyzed processes is crucial for the pharmaceutical and chemical industries. For this purpose, N-oxygenases appear as a relevant option due to their ability to oxygenate primary amines obtaining partially or fully oxygenated derivatives. Streptomyces, which constitute the main source of these enzymes, are microorganisms involved in the biosynthesis of antibiotics and other relevant secondary metabolites. In this study, agarose-immobilized Streptomyces griseus whole cells were utilized as a biocatalyst with N-oxygenase activity. To enhance enzymatic performance, the system was stimulated with extracellular media derived from microbial cocultures, aiming to induce secondary metabolism. Specifically, the addition of cell-free broths from S. griseus : Bacillus cereus cocultures (70 : 30 w/w) resulted in p-aminobenzoic acid to p-nitrobenzoic acid conversion yields exceeding 60%, demonstrating the efficacy of coculture-derived elicitors in modulating enzymatic performance. Taken together, these characteristics make this biocatalyst a promising candidate for N-oxygenation reactions on a preparative scale.