The alkane-assimilating yeast Yarrowia lipolytica degrades very efficiently hydrophobic substrates such as n-alkanes, fatty acids, fats and oils for which it has specific metabolic pathways. An overview of the oxidative degradation pathways for alkanes and triglycerides in Y. lipolytica is given, with new insights arising from the recent genome sequencing of this yeast. This includes the interaction of hydrophobic substrates with yeast cells, their uptake and transport, the primary alkane oxidation to the corresponding fatty alcohols and then by different enzymes to fatty acids, and the subsequent degradation in peroxisomal beta-oxidation or storage into lipid bodies. Several enzymes involved in hydrophobic substrate utilisation belong to multigene families, such as lipases/esterases (LIP genes), cytochromes P450 (ALK genes) and peroxisomal acyl-CoA oxidases (POX genes). Examples are presented demonstrating that wild-type and genetically engineered strains of Y. lipolytica can be used for alkane and fatty-acid bioconversion, such as aroma production, for production of SCP and SCO, for citric acid production, in bioremediation, in fine chemistry, for steroid biotransformation, and in food industry. These examples demonstrate distinct advantages of Y. lipolytica for their use in bioconversion reactions of biotechnologically interesting hydrophobic substrates.

Continuous low-level supply or in situ generation of hydrogen peroxide (H2O2) is essential for the stability of unspecific peroxygenases, which are deemed ideal biocatalysts for the selective activation of C–H bonds. To envisage potential large scale applications of combined catalytic systems the reactions need to be simple, efficient and produce minimal by-products. We show that gold-palladium nanoparticles supported on TiO2 or carbon have sufficient activity at ambient temperature and pressure to generate H2O2 from H2 and O2 and supply the oxidant to the engineered unspecific heme-thiolate peroxygenase PaDa-I. This tandem catalyst combination facilitates efficient oxidation of a range of C-H bonds to hydroxylated products in one reaction vessel with only water as a by-product under conditions that could be easily scaled.

Covering: up to end of June 2018Baeyer-Villiger monooxygenases (BVMOs) are flavin-dependent enzymes that catalyse the oxidation of ketones and cyclic ketones to esters and lactones, respectively, by using molecular oxygen and NAD(P)H. BVMOs also catalyse sulfoxidations and N-oxidations. BVMOs are widely studied as attractive biocatalysts, but also catalyse key reactions in metabolic pathways of the organisms from which they are sourced. BVMOs are involved in the primary metabolism of atypical carbon sources, thereby conferring an evolutionary advantage to the host organism. In addition, BVMOs catalyse a plethora of diverse Baeyer-Villiger and heteroatom oxidations in the construction of complex secondary metabolites. These natural products often have attractive biological properties, such as anti-bacterial, anti-cancer and anti-proliferative activity, and can have clinical applications. In contrast, BVMOs are also involved in the synthesis of microbial toxins. This review will discuss the inherent roles of type I, type II and type O BVMOs in the metabolism of microorganisms.