Bicarbonate ions are the primary source of inorganic carbon for autotrophic organisms living in aquatic environments. In the present study, we evaluated the short-term (hours) effects of sodium bicarbonate (NaHCO₃) addition on the growth and photosynthetic efficiency of the green algae Chlorella sorokiniana (211/8k). Bicarbonate was added to nonaxenic cultures at concentrations of 1, 2, and 3 g L⁻¹ leading to a significant increase in biomass especially at the highest salt concentration (3 g L⁻¹) and also showing a bactericidal and bacteriostatic effect that helped to keep a reduced microbial load in the algal culture. Furthermore, bicarbonate stimulated the increase in cellular content of chlorophyll a, improving the photosynthetic performance of cells. Since microalgae of genus Chlorella spp. show great industrial potential for the production of biofuels, nutraceuticals, cosmetics, health, and dietary supplements and the use of bicarbonate as a source of inorganic carbon led to short-term responses in Chlorella sorokiniana, this method represents a valid alternative not only to the insufflation of carbon dioxide for the intensive cultures but also for the production of potentially bioactive compounds in a short period.

Marine invertebrates are a traditional source of natural products with relevant biological properties. Tunicates are soft-bodied, solitary or colonial, sessile organisms that provide compounds unique in their structure and activity. The aim of this work was to investigate the chemical composition of the ascidian Cystodytes dellechiajei, selected on the basis of a positive result in biological screening for ligands of relevant receptors of the innate immune system, including TLR2, TLR4, dectin-1b, and TREM2. Bioassay-guided screening of this tunicate extract yielded two known pyridoacridine alkaloids, shermilamine B (1) and N-deacetylshermilamine B (2), and a family of methyl-branched cerebrosides (3). Compounds 2 and 3 showed selective binding to TREM2 in a dose-dependent manner. N-deacetylshermilamine B (2), together with its acetylated analogue, shermilamine B (1), was also strongly cytotoxic against multiple myeloma cell lines. TREM2 is involved in immunomodulatory processes and neurodegenerative diseases. N-deacetylshermilamine B (2) is the first example of a polycyclic alkaloid to show an affinity for this receptor.