Nutrient Deficiency and an Algicidal Bacterium Improved the Lipid Profiles of a Novel Promising Oleaginous Dinoflagellate, Prorocentrum donghaiense, for Biodiesel Production

Abstract

The lipid production potential of 8 microalgae species was investigated. Among these eight species, the best strain was a dominant bloom-causing dinoflagellate, Prorocentrum donghaiense ; this species had a lipid content of 49.32±1.99% and exhibited a lipid productivity of 95.47±0.99 mg L −1 d −1 , which was 2-fold higher than the corresponding values obtained for the oleaginous microalgae Nannochloropsis gaditana and Phaeodactylum tricornutum . P. donghaiense, which is enriched in C16:0 and C22:6, is appropriate for commercial DHA production. Nitrogen or phosphorus stress markedly induced lipid accumulation to levels surpassing 75% of the dry weight, increased the C18:0 and C17:1 contents, and decreased the C18:5 and C22:6 contents, and these effects resulted in decreases in the unsaturated fatty-acid levels and changes in the lipid properties of P. donghaiense such that the species met the biodiesel specification standards. Compared with the results obtained under N-deficient conditions, the enhancement in the activity of alkaline phosphatase of P. donghaiense observed under P-deficient conditions could partly alleviate the adverse effects on the photosynthetic system exerted by P deficiency to induce the production of more carbohydrates for lipogenesis. The supernatant of the algicidal bacterium Paracoccus sp. Y42 culture lysed P. donghaiense without decreasing its lipid content, which resulted in facilitation of the downstream oil extraction process and energy savings through the lysis of algal cells. The Y42 supernatant treatment improved the lipid profiles of algal cells by increasing their C16:0, C18:0 and C18:1 contents and decreasing their C18:5 and C22:6 contents, which is favourable for biodiesel production. IMPORTANCE This study demonstrates the high potential of P. donghaiense , a dominant bloom-causing dinoflagellate, for lipid production. Compared with previously studied oleaginous microalgae, P. donghaiense exhibit greater potential for practical application due to its higher biomass and lipid contents. Nutrient deficiency and the algicidal bacterium Paracoccus sp. Y42 could improve the suitability of the lipid profile of P. donghaiense for biodiesel production. Furthermore, Paracoccus sp. Y42 effectively lyse algal cells, which facilitates the downstream oil extraction process for biodiesel production and results in energy savings through the lysing of algal cells. This study provides a more promising candidate for the production of DHA for human nutritional products and of microalgal biofuel, as well as a more cost-effective method for breaking algal cells. The high lipid productivity of P. donghaiense and algal cell lysis by algicidal bacteria contribute to reductions in the production cost of microalgal oil.

Algicidal Bacteria: A Review of Current Knowledge and Applications to Control Harmful Algal Blooms

“…Recent examples of this approach for algal lipid production include the use of P. pseudoalcaligenes AD6 and Aeromonas hydrophila AD9, both isolated from shallow wetland sediments ( Lenneman et al, 2014 ), Paracoccus sp. strain Y42 ( Gui et al, 2021 ), Labrenzia sp. for lysis of diatom P. tricornutum ( Chen et al, 2015 ), and Sagittula stellata , which was isolated from an area with persistent algal blooms ( Wang et al, 2021 ).…”

Chronological age-related metabolome responses in the dinoflagellate Karenia mikimotoi, can predict future bloom demise

“…Furthermore, smaller size may confer NP-rep cells a competitive advantage over larger cells because of higher surface area-to-volume ratio and smaller thickness of the diffusion boundary layer 23 . Enlargement of cell size has been observed in dinoflagellate K. mikimotoi 16 , Amphidinium carterae 24 , and Prorocentrum donghaiense under P starvation 22 . In addition, P. donghaiense cells showed retardation of photosynthetic parameters (e.g., concentrations of chlorophyl a and carotenoid, Fv/Fm and rETR) under P and N deficiency 22 .…”

“…Enlargement of cell size has been observed in dinoflagellate K. mikimotoi 16 , Amphidinium carterae 24 , and Prorocentrum donghaiense under P starvation 22 . In addition, P. donghaiense cells showed retardation of photosynthetic parameters (e.g., concentrations of chlorophyl a and carotenoid, Fv/Fm and rETR) under P and N deficiency 22 . Collectively, alteration in cell size or chloroplast conditions may be indicative of nutrient deficient stress in dinoflagellates.…”

“…1 and 2). The low cell density of K. mikimotoi in both nutrient-deficient groups may be compensated by its large size and high volume 22 . Furthermore, smaller size may confer NP-rep cells a competitive advantage over larger cells because of higher surface area-to-volume ratio and smaller thickness of the diffusion boundary layer 23 .…”

Distribution, screening and biochemical characterization of indigenous microalgae for bio-mass and bio-energy production potential from three districts of Pakistan

“…Protein from selected microalgal isolates was extracted by alkaline extraction method and extracted proteins were quantified by Bradford assay. Another study also used the similar procedure for protein quantification (Tang et al, 2020;Gui et al, 2021). Among the 23 cultivated strains, the isolate AIN128 (Scenedesmus) strain showed higher protein content (42.91%) while isolates AIN24 (Botryrococcus), AIN163 (Selenastrum) and AIN143 (Chlorococcum) were the second, third and fourth highest protein producer (25.96%, 25.63% and 24.96%, respectively).…”