Harnessing melanin from deep-sea yeast Hortaea werneckii NIOT129A8: Heavy metal adsorption potential

Marine organisms are recognized for their unique ability to detoxify heavy metals through chelation, effectively sequestering and reducing metal ion toxicity. This study focuses on the deep-sea yeast Hortaea werneckii NIOT129A8, which exhibits a unique adaptation for melanin production, a compound known for its chelating properties that can be harnessed to sequester and detoxify metal ions. Sequencing of the internal transcribed spacer (ITS) region and translation elongation factor (TEF) gene showed similarity of 99.2 % and 96.1 %, respectively with H. werneckii type strain CBS 107.67, presenting it as a potentially new strain from the deep sea. Growth conditions were optimized to maximize melanised biomass production, targeting cost-effective media. The study employed diverse spectroscopic analyses such as EPR, FTIR and NMR, to confirm the presence and structural properties of melanin within the yeast. The melanised ghost cells demonstrated effective shielding against UV-C exposure and maintained 50-70 % E. coli growth across various exposure times. An analysis of H. werneckii biomass treatments with NaOH and phosphorylation was conducted to evaluate their efficiency in heavy metal biosorption in which the former exhibited high removal efficiencies for Cu²⁺ (79 %), Pb²⁺ (76 %), Cr⁶⁺ (75 %), Cd²⁺ (74 %), Ni²⁺ (73 %), and Co²⁺ (69 %), emphasizing the importance of pretreatment in enhancing adsorption properties. The findings highlight the potential of deep-sea yeast strain NIOT129A8 as a bio-adsorbent in bioremediation applications, particularly due to its adaptability, cost-effective production, and high metal-binding efficiencies.