Semi-continuous cultivation of EPS-producing marine cyanobacteria: A green biotechnology to remove dissolved metals obtaining metal-organic materials

Matilde Ciani; Francesca Decorosi; Claudio Ratti; Roberto De Philippis; Alessandra Adessi

doi:10.1016/j.nbt.2024.04.004

Semi-continuous cultivation of EPS-producing marine cyanobacteria: A green biotechnology to remove dissolved metals obtaining metal-organic materials

N Biotechnol. 2024 May 5:82:33-42. doi: 10.1016/j.nbt.2024.04.004. Online ahead of print.

Authors

Matilde Ciani¹, Francesca Decorosi², Claudio Ratti³, Roberto De Philippis¹, Alessandra Adessi⁴

Affiliations

¹ Department of Agriculture, Food, Environment and Forestry (DAGRI), University of Florence, Piazzale delle Cascine, 18, 50144 Florence, Italy.
² Genexpress Laboratory, Department of Agronomy, Food, Environmental and Forestry Sciences (DAGRI), University of Florence, I-50019 Sesto Fiorentino, Italy.
³ Department of Agricultural and Food Sciences, University of Bologna, Viale G. Fanin, 40, 40127 Bologna, Italy.
⁴ Department of Agriculture, Food, Environment and Forestry (DAGRI), University of Florence, Piazzale delle Cascine, 18, 50144 Florence, Italy. Electronic address: alessandra.adessi@unifi.it.

PMID: 38714292
DOI: 10.1016/j.nbt.2024.04.004

Abstract

Given the necessity for bioprocesses scaling-up, the present study aims to explore the potential of three marine cyanobacteria and a consortium, cultivated in semi-continuous mode, as a green approach for i) continuous exopolysaccharide-rich biomass production and ii) removal of positively charged metals (Cu, Ni, Zn) from mono and multi-metallic solutions. To ensure the effectiveness of both cellular and released exopolysaccharides, weekly harvested whole cultures were confined in dialysis tubings. The results revealed that all the tested cyanobacteria have a stronger affinity towards Cu in mono and three-metal systems. Despite the amount of metals removed per gram of biomass decreased with higher biosorbent dosage, the more soluble carbohydrates were produced, the greater was the metal uptake, underscoring the pivotal role of released exopolysaccharides in metal biosorption. According to this, Dactylococcopsis salina 16Som2 showed the highest carbohydrate productivity (142 mg L^-1 d^-1) and metal uptake (84 mg Cu g^-1 biomass) representing a promising candidate for further studies. The semi-continuous cultivation of marine cyanobacteria here reported assures a schedulable production of exopolysaccharide-rich biosorbents with high metal removal and recovery potential, even from multi-metallic solutions, as a step forward in the industrial application of cyanobacteria.

Keywords: Biosorption; Exopolysaccharides; Heavy metal; Marine cyanobacteria; Semi-continuous cultivation.