Effect of Ca2+ concentration on Scenedesmus sp. growth in heterotrophic and photoautotrophic cultivation

Publication date: Available online 14 September 2017
Source:New Biotechnology
Author(s): Fabrizio Di Caprio, Pietro Altimari, Francesca Pagnanelli
The influence of Ca²⁺ concentration on the growth of the microalga Scenedesmus sp. in heterotrophic and photoautotrophic cultivations was investigated. Heterotrophic growth was induced by the addition of olive mill wastewaters (9% v·v⁻¹) to the culture. Variations in the calcium concentration affected differently biomass production depending on whether microalgae were cultivated under heterotrophic or photoautotrophic regime. In photoautotrophic regime, increasing the calcium concentration from 20 to 230mg/L decreased maximum cell concentration and growth rate. In heterotrophic cultivation, cell concentration and growth rate decreased with Ca²⁺ concentration increasing from 20 to 80mg/L but then increased with Ca²⁺ concentration increasing to 230mg/L. Increasing calcium concentration invariably promoted cell aggregation. The precipitation of calcium phosphates can explain the decreasing growth rate and cell concentration attained with increasing calcium concentration, while the influence of Ca²⁺ concentration on the adsorption of phenols on suspended solids can explain the enhanced growth attained at large Ca²⁺ concentration under heterotrophic regime. Implications of the illustrated results for industrial scale application of microalgae are thoroughly discussed.



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