Screening of High Temperature-Tolerant Oleaginous Diatoms

Abstract

Screening suitable strains with high temperature adaptability is of great importance for reducing the cost of temperature control in microalgae cultivation, especially in summer. To obtain high temperature-tolerant diatoms, water samples were collected in summer from 7 different regions of China across the Northeast, North and East. A total of 731 water samples was collected and from them 131 diatom strains were isolated and identified based on the 18S rRNA sequences. Forty-nine strains out of the 131 diatoms could survive at 30°C, and 6 strains with relatively high biomass and lipid content at high temperature were selected and were found to be able to grow at 35°C. Cyclotella sp. HB162 had the highest dry biomass of 0.46 g/l and relatively high triacylglycerol (TAG) content of 237.4 mg/g dry biomass. The highest TAG content of 246.4 mg/g dry biomass was obtained in Fistulifera sp. HB236, while Nitzschia palea HB170 had high dry biomass (0.33 g/l) but relatively low TAG content (105.9 mg/g dry biomass). N. palea HB170 and Fistulifera sp. HB236 presented relatively stable growth rates and lipid yields under fluctuating temperatures ranging from 28 to 35°C, while Cyclotella HB162 maintained high lipid yield at temperatures below 25°C. The percentage of saturated fatty acids and monounsaturated fatty acids in all the 6 strains was 84-91% in total lipids and 90-94% in TAGs, which makes them the ideal feedstock for biodiesel.

Ecophysiological and Cell Biological Traits of Benthic Diatoms From Coastal Wetlands of the Southern Baltic Sea

“…The extent to which TAGs are produced is species-and strain-specific (Hu et al, 2008), as not every species is able to produce and accumulate TAGs in high amounts. Zhang et al (2020) studied highly oleaginous diatom strains adapted to high temperatures. While the highest TAG content was obtained at 246.4 mg/g dry biomass (Fistulifera sp.…”

Molecular species composition of polar lipids from two microalgae Nitzschia palea and Scenedesmus costatus using HPLC-ESI-MS/MS

“…It was thus obtained two very different profiles, in which we find respectively the predominance of 16:1, 20:2 and 20:5, then to a lesser extent 16:0 and 18:1 for the diatom (N. palea), and a majority of 16:4 and 18:3, followed by 16:0, 18:1 and 18:2 for the green algae (S. costatus). Zhang et al (2020) showed that six different diatom strains exhibited fatty acid compositions typical of the class Bacillariophyceae, with a majority of 14:0, 16:0, 16:1, and 20:5. Among these strains, the authors identified N. palea HB170, which showed a fatty acid composition in agreement with our observations, although in our study we focused on polar lipids while Zhang et al (2020) determined the total fatty acid content or that derived from triglycerides alone.…”

“…Zhang et al (2020) showed that six different diatom strains exhibited fatty acid compositions typical of the class Bacillariophyceae, with a majority of 14:0, 16:0, 16:1, and 20:5. Among these strains, the authors identified N. palea HB170, which showed a fatty acid composition in agreement with our observations, although in our study we focused on polar lipids while Zhang et al (2020) determined the total fatty acid content or that derived from triglycerides alone. Regarding green algae, Sato et al (1995) previously reported the occurrence of pinolenic acid (18:3n-6) and coniferonic acid (18:4n-3) in the case of Chlamydomonas reinhardtii.…”