Due to the overexploitation of industrial fisheries, as the principal source of fish oil, as well as the increasing replacement of synthetic pigments for animal nutrition, we need to find sustainable sources for these essential nutrient productions. Marine Rhodotorula strains NCYC4007 and NCYC1146 were used to determine the biosynthesis of docosahexaenoic acid (DHA) and carotenoids by biotransforming raw glycerol, a waste product of biodiesel. To evaluate the presence of inhibitory substances in raw glycerol, both strains were also grown in the presence of analytical grade glycerol and glucose as the main carbon source separately. With raw glycerol, NCYC4007 showed a significant correlation between DHA production and intracellular phosphorous concentrations. NCYC1146, a new Rhodotorula strain genetically described in this work, can produce canthaxanthin but only when glycerol is used as a main carbon source. Then, NCYC4007 could synthesize DHA as a phospholipid, and the production of canthaxanthin depends on the kind of carbon source used by NCYC1146. Finally, malate dehydrogenase activity and glucose production can be used as a proxy of the metabolisms in these marine Rhodotorula. This is the first evidence that marine Rhodotorula are capable of synthesizing DHA and canthaxanthin using an alternative and low-cost source of carbon to potentially scale their sustainable production for animal nutrition.

Expansion of oxygen minimum zones in the world's oceans is likely to enhance the production of anaerobic metabolites by marine microorganisms. Here we show that toluene is present throughout the year in shelf waters of the upwelling ecosystem off Concepción (36° S), Chile, and it is a product of microbial anaerobic metabolism. The intra-annual variability in toluene concentrations is consistent with seasonal variability in the strengths of suboxic equatorial and oxygenated subantarctic water masses. Laboratory incubations of oxygen minimum zone water showed microbial production of toluene in the absence of O₂. Toluene concentrations were elevated (up to 96 nM) in deeper O₂-depleted waters and followed a seasonal pattern in oceanographic conditions. There is evidence to hypothesize that microbial production of toluene could be a homeostatic biochemical mechanism to thrive in the more acidic oxygen minimum zone waters. On the other hand, evidence indicates that microbial anaerobic degradation of toluene may be a source of NO₂⁻ by partial denitrification, as shown for aquifer sediments. Since toluene production was not detected in incubations under aerobic conditions, we hypothesize that oxygen minimum zone waters export toluene to surrounding oxygenated waters. Expansion of hypoxia in the ocean will certainly enhance the production and export of anaerobic metabolites by marine microorganisms.

Expansion of oxygen minimum zones (OMZ) in the world´s oceans is likely to enhance production of anaerobic metabolites by marine microorganisms. Here we show that the aromatic hydrocarbon toluene is present throughout the year in shelf waters of the upwelling ecosystem of the Humboldt Current System off Concepción (36ºS), Chile, and it is a product of microbial anaerobic metabolism of the water column. The intra-annual variability in toluene concentrations within the water column is consistent with seasonal variability in the relative strengths of suboxic equatorial and well-oxygenated subantarctic water masses that interact in the study area. These observations were complemented with data from laboratory incubations of OMZ water –– showing microbial production of toluene in the absence of O₂. Toluene concentrations were elevated in deeper O₂-depleted waters and followed a seasonal pattern. Toluene was also detected in the oxygenated waters of subantarctic origin that impinge on the continental shelf and replace OMZ waters every year during austral winter. Since toluene production was not detected in incubations under aerobic conditions, we hypothesize that OMZ waters export toluene to surrounding oxygenated waters. Expansion of OMZ waters in the world will certainly enhance production and export of anaerobic metabolites by marine microorganisms.