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BACKGROUNDOver 90% of microalgae cultivations on a commercial scale are grown in outdoor systems, which means that the performance of these bioprocesses is dependent on the climatic conditions in each particular locality. Thus, the selection of suitable locations according to their climatic conditions is extremely important to develop technically and economically viable processes. This study aimed to assess the influence of geographic position and local climate on the microalgae culture performance in photobioreactors, as a strategy to map potential regions for commercial‐scale microalgae production. Six extreme positions of Brazil were chosen to represent their respective climates in the four seasons of the year.RESULTSThe climatic variables considered were temperature, light irradiance, and photoperiod. In terms of both biomass and lipid production in an annual overview, the results showed that tropical climates and low latitudes favor the microalgae culture. The highest annual average biomass productivity (0.278 g L−1 d−1) and annual average lipid productivity (0.056 g L−1 d−1) were recorded in Boa Vista‐RR (02° 49′ 12″ N), in summer.CONCLUSIONThe geographic position and the local climate are decisive criteria in the performance of these processes, being able to increase up to three and four times the biomass productivity and lipid productivity, respectively. © 2020 Society of Chemical Industry

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The aim of this work was evaluate the role of photoperiods (long-term, frequencies and short) on the growth and lipid content of microalgae Scenedesmus obliquus CPCC05. The results showed that Scenedesmus obliquus can store sufficient energy to sustain cell growth for continuous periods of up to 2h in the dark, without affecting the photosynthetic rate. The values for maximum biomass (9.58mg/Lh) and lipid productivities (2.56mg/Lh) were obtained at photoperiod of 0.91:0.09s (light:dark) and 48 t/d, respectively. Moreover, the best trade-offs between biomass productivity and light energy economy occurred in photoperiods of 0.5:0.5s and 0.91:0.09s (light:dark), and those between lipid productivity and light energy economy occurred in the frequency photoperiod of 24 and 48 t/d. Thus, the use of the photoperiods are an effective strategy for reducing costs of microalgal biomass production.

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Different cultivation strategies have been developed with the aim of increasing the production rate of microalgal pigments. Specifically, biotechnological approaches are designed to increase antioxidant metabolites as chlorophyll and carotenoids. However, although significant advances have been built up, available information regarding both the chlorophyll metabolism and their oxidative reactions in photobioreactors is scarce. To unravel such processes, the detailed chlorophyll and carotenoid fraction of Scenedesmus obliquus has been studied by HPLC-ESI/APCI-hrTOF-MS from phototrophic and heterotrophic cultures. Scenedesmus is provided with a controlled strategy of interconversion between chlorophyll a and b to avoid the formation of reactive oxygen species (ROS) at high irradiances in addition to the photoacclimation of carotenoids. Indeed, precise kinetics of 132-hydroxy- and 151-hydroxy-lactone chlorophyll metabolites shows the existence of a chlorophyll oxidative metabolism as a tool to manage the excess of energy at high light conditions. Unexpectedly, the oxidation under phototrophy favored chlorophyll b metabolites over the chlorophyll a series, while the heterotrophic conditions exclusively induced the formation of 132-hydroxy-chlorophyll a. In parallel, during the first 48 h of growth in the dark, the chlorophyll fraction maintained a promising steady state. Although future studies are required to resolve the biochemical reactions implied in the chlorophyll oxidative metabolism, the present results agree with phytoplankton metabolism.

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