Biocatalytic production of lactones, and in particular ϵ‐caprolactone (CL), have gained increasing interest as a greener route to polymer building blocks, especially through the use of Baeyer–Villiger monooxygenases (BVMOs). Despite several advances in the field, BVMOs, however, still suffer several practical limitations. Alcohol dehydrogenase (ADH)‐mediated lactonization of diols in turn has received far less attention and very few enzymes have been identified for the conversion of diols to lactones, with horse‐liver ADH (HLADH) remaining the catalyst of choice. Screening of a diverse panel of ADHs, AaSDR‐1, a member of the short‐chain dehydrogenase/reductase family, was found to produce ϵ‐caprolactone from hexane‐1,6‐diol. Moreover, cofactor regeneration by an NADH oxidase eliminated the requirement of co‐substrates, yielding water as the sole by‐product. Despite lower turnover frequencies as compared to HLADH, higher selectivity was found for the production of CL, with HLADH forming significant amounts of 6‐hydroxyhexanoic acid and adipic acid through aldehyde dehydrogenation/oxidation of the gem‐diol intermediates. Also, CL yield were shown to be dependent on buffer choice, as structural elucidation of a Tris adduct confirmed the buffer amine to react with aliphatic aldehydes forming a Schiff‐base intermediate which through further ADH oxidation, forms a tricyclic acetal product.

The Southern Ocean (SO) distributes climate signals and nutrients worldwide, playing a pivotal role in global carbon sequestration. Microbial communities are essential mediators of primary productivity and carbon sequestration, yet we lack a comprehensive understanding of microbial diversity and functionality in the SO. Here, we examine contemporary studies in this unique polar system, focusing on prokaryotic communities and their relationships with other trophic levels (i.e. phytoplankton and viruses). Strong seasonal variations and the characteristic features of this ocean are directly linked to community composition and ecosystem functions. Specifically, we discuss characteristics of SO microbial communities and emphasise differences from the Arctic Ocean microbiome. We highlight the importance of abundant bacteria in recycling photosynthetically derived organic matter. These heterotrophs appear to control carbon flux to higher trophic levels when light and iron availability favour primary production in spring and summer. Conversely, during winter, evidence suggests that chemolithoautotrophs contribute to prokaryotic production in Antarctic waters. We conclude by reviewing the effects of climate change on marine microbiota in the SO.

The biological carbon pump is crucial for the export of particulate organic matter in the ocean. Recent studies on marine microbes have shown the profound influence of bacteria and archaea as regulators of particulate organic matter export.