Potential of Lipid Biosynthesis under Heterotrophy in the Marine Diatom Cyclotella cryptica.

Despite the theoretical high productivity, microalgae-based oil production is not economically sustainable due to the high cost of photoautotrophic cultures. Heterotrophic growth is a suitable economic alternative to overcoming light dependence and climatic/geographic fluctuations. Here we report data about growth performance, biomass production, and lipid composition of the marine diatom Cyclotella cryptica, chosen as a model strain for biodiesel production in heterothrophy. A repeated-batch process of heterotrophic cultivation has also been investigated to assess the robustness and phenotypic stability. The process consisting of six constant cycle repetitions was carried out for 42 days and led to an average dry biomass production of 1.5 ± 0.1 g L-1 of which 20% lipids composed of 60% triglycerides, 20% phospholipids. and 20% glycolipids. The major fatty acids were C16:0 (∼26%), C16:1 ω-7 (∼57%), and C20:5 ω-3 (∼12%), with a significant reduction in the unsaturated fatty acids in comparison to other microalgae grown in heterotrophy. Fatty acids were differently distributed among the glycerolipid classes, and the lipid composition was used to compare the potential properties of C. cryptica oil with traditional vegetable biofuels.

Evaluation of the alkalinity stress tolerance of three Brassica rapa CAX1 TILLING mutants.

Alkalinity is an important environmental factor that affects crop production and will be exacerbated in the current climate change scenario. Thus, the presence of carbonates and high pH in soils negatively impacts nutrient assimilation and photosynthesis and causes oxidative stress. A potential strategy to improve tolerance to alkalinity could be the modification of cation exchanger (CAX) activity, given that these transporters are involved in calcium (Ca2+) signaling under stresses. In this study, we used three Brassica rapa mutants (BraA.cax1a-4, BraA.cax1a-7, and BraA.cax1a-12) from the parental line 'R-o-18' that were generated by Targeting Induced Local Lesions in Genomes (TILLING) and grown under control and alkaline conditions. The objective was to assess the tolerance of these mutants to alkalinity stress. Biomass, nutrient accumulation, oxidative stress, and photosynthesis parameters were analyzed. The results showed that BraA.cax1a-7 mutation was negative for alkalinity tolerance because it reduced plant biomass, increased oxidative stress, partially inhibited antioxidant response, and lowered photosynthesis performance. Conversely, the BraA.cax1a-12 mutation increased plant biomass and Ca2+ accumulation, reduced oxidative stress, and improved antioxidant response and photosynthesis performance. Hence, this study identifies BraA.cax1a-12 as a useful CAX1 mutation to enhance the tolerance of plants grown under alkaline conditions.