Isolation and Optimized Cultivation of the Freshwater Diatom Nitzschia palea HY1 for Increased Biomass and Fucoxanthin Production

Abstract

Diatoms are globally distributed microalgae recognized as potential sources of biomass, lipids, and high-value compounds. While marine diatoms have been extensively studied, freshwater diatoms are also promising sources of valuable compounds. In this study, we isolated a novel freshwater diatom strain, named Nitzschia palea HY1, from Jungnangcheon Stream in Seoul, South Korea. The strain was characterized by phylogenetic analysis and morphological examination using light and electron microscopy. When grown on freshwater diatom medium (FDM), N. palea HY1 exhibited higher biomass (0.68 g L-1) and fucoxanthin production (9.19 mg L-1) compared to previous reports on N. palea. Furthermore, increasing the NaHCO3 concentration from 2 to 10 mM in the modified freshwater diatom medium (MFDM) resulted in a 3-fold increase in maximum biomass and an 80% increase in fucoxanthin productivity. Further improvement was achieved by adding 2% CO2 and air bubbling to the MFDM, resulting in even higher biomass and fucoxanthin yields. These results suggest that by optimizing culture conditions using MFDM and agitation, N. palea HY1 has the potential as an alternative source to marine organisms for biomass and fucoxanthin production.