Depiction of growth specific changes in concentration of storage products in centric marine diatom Chaetoceros gracilis

Chaetoceros, with >232 identified species is one of the largest genera of planktonic diatoms playing a pivotal role in aquatic ecosystem. Known for its high metabolite content and suitability as fish feed, C. gracilis, has been chosen for this study to comprehend the variation in carbon utilization and accumulation of reserve compounds at different growth stages of the alga. The uptake and influence of two discrete sources of silica on cellular growth and metabolite production was also analyzed. The result showed that the growth rate (0.27 d-1) and cell number (132 x 105 cells mL-1) of the cultures supplemented with nano-fabricated silica was higher than those with meta silicate. Concurrently both biomass and lipid productivity (0.082 and 0.043 g L-1 d-1) was also found to be higher in the former culture setup. The study further indicates both the extracellular polymeric substances (EPS), and storage lipid content was maximized during the late exponential and stationary phase. Though the bound EPS content was higher in the cultures supplemented with nano silica (0.095 g L-1), the level of unbound EPS and lipid % dry weight was higher in cultures with sodium meta silicate (1.33 g L-1 and 40.25%, respec-tively). Thus, the results provide evidence that how co-accumulation of metabolites are closely correlated to the growth cycle of diatoms and that commercial production of such highly valuable compounds can be achieved by targeting the specific growth phase even in outdoor setups.

Automated summary

This study focused on the variation in carbon utilization and accumulation of reserve compounds in the diatom C. gracilis at different growth stages, as well as the impact of two different sources of silica. The results showed that nano-fabricated silica had a higher growth rate and cell number, as well as higher biomass and lipid productivity, compared to meta silicate. The study also found that the maximum production of extracellular polymeric substances and storage lipid content occurred during the late exponential and stationary phases.