Isolation and identification of green alga Chlorella vulgaris HNUFU001 for environmental selenium enrichment in heterotrophic growth regime

Abstract

Microalgae, particularly Chlorella, have promising selenium (Se) enrichment capacity and great potential in wastewater treatment and the development of nutraceuticals. To acquire Chlorella strains with strong heterotrophic propensity and robust Se tolerance, this research utilized a heterotrophic isolation strategy along with a high Se concentration medium as selection factors. The combined sequence of the ribosomal small subunit (SSU) and internal transcribed spacer (ITS) was utilized for phylogenetic analysis, and comparative analysis of ITS secondary structures was also integrated to identify the desired strain. A novel subtropical microalgal strain, Chlorella vulgaris HNUFU001 with high Se tolerance, was isolated from water samples in a lake at Hainan University, China. Gaussian process regression was utilized to assess the strain's growth under varying Se concentrations. The intracellular accumulation and extracellular removal of Se were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), respectively. The maximum intracellular organic Se (92 % of total Se) was observed as 108.835 μg/g dry weight (DW) for 1 mg/L Se treatment. The highest Se removal rate was 40 %. The high Se tolerance and enrichment traits enable Chlorella vulgaris HNUFU001 to be a promising candidate for the heterotrophic production of organic Se-related nutraceuticals.