Selection and characterization of acid-tolerant Chlorophyta division microalgae for potential metabolites production in a bubble column bioreactor: A ready-to-industrial scale screening

Microalgae are promising candidates for sustainable bioprocesses owing to their ability to capture/utilize CO2 and produce valuable metabolites. However, strain-to-strain variability poses a challenge to industrial scalability. This paper reports a study on the screening of 28 Chlorophyta microalgal strains from six species cultivated under standardized semi-continuous conditions in a bubble column bioreactor. Growth kinetics, nitrogen uptake, and metabolite accumulation were analyzed to identify strains characterized by promising biomass/metabolite productivities. The results indicated two distinct kinetic behaviors: a large fraction of the investigated strains was characterized by a common biomass/nitrate uptake behavior, and a subset of the strain pool was characterized by atypical nitrogen assimilation patterns. Strains characterized by high biomass growth rates are characterized by high lipid productivity. Strains with intermediate biomass growth rates are characterized by high carbohydrate accumulation. Chlorella vulgaris (ACUF 058) and Chloroidium saccharophilum (ACUF 050) emerged as strong candidates for carbohydrate and protein production, respectively. This study proposed a systematic procedure for strain selection, bridging laboratory screening, and industrial feasibility. These results emphasize the role of tailored cultivation strategies in optimizing biomass yield and metabolite productivity. Further research integrating genomic and proteomic insights will enhance strain-specific process optimization, facilitating the large-scale deployment of microalgal bioprocesses.