No abstract

No abstract

No abstract

The growth, lipid accumulation and bioproducts of the marine diatom Halamphora coffeaeformis were evaluated in a hybrid two-stage culture using seawater enriched with nutrients and without vitamins. The influence of dissolved and internal nutrients on growth and lipid accumulation was also analyzed. Total lipid content increased in the declining phase up to 33.4% ash-free dry weight, due to an increase in neutral lipids, which reached 87% of total lipids. The observed delay in triacylglycerol (TAG) accumulation could be explained by the accumulation of large internal pools of nitrogen in H. coffeaeformis. TAG, frustules (silica-containing cell wall) and soluble exopolysaccharides are analyzed and proposed as bioproducts of commercial interest. A biorefinery approach for the economic and environmentally sustainable production of biodiesel from the hybrid two-stage culture of H. coffeaeformis is suggested.

No abstract

No abstract

Omega-3 eicosapentaenoic fatty acid (C20:5; EPA), β-glucan and fucoxanthin have received widespread attention owing to their potential industrial applications; however, their availability is currently limited to unsustainable sources such as fish oils and macroalgae. Though some species of diatoms are also a natural source of these metabolites, progress needs to be made in reducing the cost barriers involved in their large-scale production. The aim of the present study was therefore to assess the potential of the marine diatom Halamphora coffeaeformis to simultaneously accumulate EPA, chrysolaminarin and fucoxanthin in a raceway pond sustained by fertilizer (Bayfolan®)-enriched seawater. The biomass production increased significantly along the experiment, the specific growth rate, biomass productivity and areal yield being 2.03 day −1 , 0.128 g.L − 1.d −1 and 25.73 g.m −2 .d −1 , respectively. Proteins dominated in the first culture phase, while lipids, carbohydrates and pigments increased toward the end of the stationary phase. The harvested biomass presented 310 mg.g −1 DW (dry weight) of total lipids containing high amounts of EPA (24% of total fatty acids), 114 mg.g −1 DW of chrysolaminarin and 38 mg.g −1 DW of fucoxanthin. These values compare favorably with those obtained from commercially used sources. The culture medium proposed represents a non-conventional, cost-effective resource allowing for sustained high biomass levels throughout 22 days, guaranteeing the accumulation of valuable metabolites. Furthermore, the robustness and auto-flocculation capacity of the species increase the chances of viable scalability. These findings indicate the potential of H.coffeaeformis as a high-value metabolite feedstock, focusing on sustainable bioprocesses.

Biodiesel production from the microalgal oil of the estuarine diatom Halamphora coffeaeformis has proven to be technically viable. However, a fuller understanding of the environmental factors that regulate its tolerance and neutral lipid accumulation is required for improved mass cultivation in seawater-based outdoor raceway ponds. Meteorological conditions and evaporation processes can significantly influence factors such as the salt levels, water temperature and nutrient and light availability in these systems. Laboratory experiments with H. coffeaeformis growing in f/2 medium were therefore carried out in order to evaluate the effect of temperature and salinity on its growth and tolerance ranges and the effect of salinity on its total lipid and lipid fraction content and fatty acid methyl ester profile. Results indicate that the temperature and salinity ranges of the species were 5 °C to 30 °C and 5‰ to 95‰, respectively. The optimum temperature was between 20 and 25 °C, and the optimum salinity was 20‰. Neutral lipid accumulation increased in cells adapted at 45‰ with respect to those growing at 20‰. Total lipid composition at 45 ‰ was characterized by 85.5% neutral lipids, 2.5% phospholipids and a high percentage of C16.1 (36.4% of total fatty acids). These properties are important for an adequate quality of biodiesel. The eurytolerant behaviour of H. coffeaeformis and the effect of salinity stress on its growth and neutral lipid accumulation are demonstrated. The findings indicate the beneficial attributes of this strain for the development and feasibility of seawater-based outdoor raceway ponds for biodiesel production.