Marine microalgae for outdoor biomass production—A laboratory study simulating seasonal light and temperature for the west coast of Sweden

Abstract

At Nordic latitudes, year-round outdoor cultivation of microalgae is debatable due to seasonal variations in productivity. Shall the same species/strains be used throughout the year, or shall seasonal-adapted ones be used? To elucidate this, a laboratory study was performed where two out of 167 marine microalgal strains were selected for intended cultivation at the west coast of Sweden. The two local strains belong to Nannochloropsis granulata (Ng) and Skeletonema marinoi (Sm142). They were cultivated in photobioreactors and compared in conditions simulating variations in light and temperature of a year divided into three growth seasons (spring, summer and winter). The strains grew similarly well in summer (and also in spring), but Ng produced more biomass (0.225 vs. 0.066 g DW L −1 day −1 ) which was more energy rich

Mixotrophy in a Local Strain of Nannochloropsis granulata for Renewable High-Value Biomass Production on the West Coast of Sweden

“…The increase in fatty acid content explains the increase in calorific value, from 18 to 25 MJ/kg of dry weight in these conditions, as compared to PHOTO_AIR. A calorific value of 25 MJ/kg was also reported for Ng in [17] as well as for Nannochloropsis sp. grown in Flat-Plate Photobioreactors under N, P starvation [30], thus confirming the genus as promising feedstock for biodiesel production.…”

“…For the experiments in this study, it was obtained from the culture collection GUMACC (Gothenburg University Marine Algal Culture Collection, https://www.gu.se/en/marina-vetenskaper/about-us/algal-bankgumacc, accessed on 1 November 2019). This strain was selected because it was found to be the most productive local strain on the Swedish west coast in summer conditions [17]. Ng was not axenic, but 100 µg/L of ampicillin was added at the beginning of the cultivation in order to control the bacterial growth.…”

“…The overall goal of this work was to employ mixotrophy as a strategy for maximizing the outdoor productivity of a Nannochloropsis granulata strain ( Ng ), isolated from the Skagerrak in the northeast Atlantic Ocean [ 16 ]. A previous study reported that the local Ng was the most productive strain (compared to 166 strains of Skeletonema marinoi ), in terms of both biomass yield and lipid content when cultivated in photobioreactors that simulate the light and temperature conditions during the summer on the west coast of Sweden [ 17 ]. More specifically, in summer, Ng reached 3.5 g/L of biomass containing 40% lipids, i.e., 7 and 1.5-fold, respectively, more than the most productive Skeletonema marinoi strain in the same conditions [ 17 ].…”

Blue economy in the North: Scandinavian algal biotechnology to the rescue

“…As discussed in Skogen Chauton et al (2021), this progress enables shifting the cultivation from nowadays warmer, sunnier areas to temperate to boreal regions, where either natural resources or resources of industrial origin (e.g., excess heat and CO 2 from industry) can be explored. This is exemplified in Cheregi et al (2021), where the authors compared a high number of Nordic microalgae strains with respect to their biomass production and chemical composition as a function of the growth seasons at the west coast of Sweden. The authors were able Mixotrophic cultivation, that is, combining both photosynthesis and respiration for growth and thus a higher biomass yield, is possible for some microalgal species and represents a very interesting cultivation strategy at higher latitudes.…”

Mixotrophy in diatoms: Molecular mechanism and industrial potential

“…The industrial potential of local Nordic strains for outdoor cultivation has been reviewed by Cheregi et al (2019). Most recently, a study dedicated to microalgae from Sweden's west coast revealed two species, including the diatom Skeletonema marinoi , being suitable for outdoor cultivation and biomass production for various purposes (Cheregi et al, 2021). Ongoing experiments in our laboratory investigate whether the mixotrophic cultivation could be a strategy to overcome the restricted weather condition in Nordic countries, and thus to increase biomass and lipid productivity.…”