Hybrid two-stage culture of Halamphora coffeaeformis for biodiesel production: Growth phases, nutritional stages and biorefinery approach

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.