Recombinant Expression and Characterization of a Novel Type I Baeyer–Villiger Monooxygenase from a Streptomyces Strain Isolated from the Rhizosphere of the Atacama Desert Lupinus oreophilus

The Atacama Desert is emerging as an unexpected source of microbial life and, thus, a source of bioactive compounds and novel enzymes. Baeyer-Villiger monooxygenases (BVMOs), a subclass of flavin-dependent monooxygenases (FPMOs), have gained attention as promising biocatalysts for the biosynthesis of industrially relevant molecules for a wide range of applications, such as pharmaceuticals and polymers, among others. BVMOs catalyze the oxidation of ketones and cyclic ketones to esters and lactones, respectively, by using molecular oxygen and NAD(P)H. BVMOs may also catalyze heteroatoms oxidation including sulfoxidations and <i>N</i>-oxidations. This work aims to search for novel BVMOs in the genomes of new bacterial strains isolated from the Atacama Desert. Bioinformatic analysis led to the identification of 10 putative BVMOs, where the monooxygenase named MO-G35A was selected. Genome context showed, downstream of the MO-G35A, a gene encoding for an enzyme from the short-chain dehydrogenase/reductase family, suggesting a closer redox loop between both enzymes. MO-G35A was successfully expressed in three <i>Escherichia coli</i> expression systems, where higher yields were achieved using the <i>E. coli</i> Shuffle T7 as host, suggesting that correct disulfide bond formation is necessary for correct folding. Enzyme characterization showed that it operates optimally at 35-38 °C, exhibiting a <i>Km</i> of 0.06 mM and a <i>kcat</i> of 0.15 s^-1 for bicyclo [3.2.0] hept-2-en-6-one (BHC). Furthermore, the study revealed high stability in the presence of organic solvents, making it suitable for applications in various industrial processes, especially when the substrates have poor solubility in aqueous solutions. These results highlight the robustness and adaptability of enzymes in extreme environments, making them valuable candidates for biotechnological applications.