Optimization of Microalga Chlorella vulgaris Magnetic Harvesting.

Maria G. Savvidou,Vasiliki Louli,Ioulia Georgiopoulou,Maria Myrto Dardavila,Epaminondas Voutsas,Dimitris Kekos,Haralambos Stamatis

doi:10.3390/nano11061614

Maria G. Savvidou, Vasiliki Louli + Show 5 more

Open Access

https://doi.org/10.3390/nano11061614

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Abstract

Harvesting of microalgae is a crucial step in microalgae-based mass production of different high value-added products. In the present work, magnetic harvesting of Chlorella vulgaris was investigated using microwave-synthesized naked magnetite (Fe3O4) particles with an average crystallite diameter of 20 nm. Optimization of the most important parameters of the magnetic harvesting process, namely pH, mass ratio (mr) of magnetite particles to biomass (g/g), and agitation speed (rpm) of the C. vulgaris biomass–Fe3O4 particles mixture, was performed using the response surface methodology (RSM) statistical tool. Harvesting efficiencies higher than 99% were obtained for pH 3.0 and mixing speed greater or equal to 350 rpm. Recovery of magnetic particles via detachment was shown to be feasible and the recovery particles could be reused at least five times with high harvesting efficiency. Consequently, the described harvesting approach of C. vulgaris cells leads to an efficient, simple, and quick process, that does not impair the quality of the harvested biomass.

Highlights

Microalgae have been extensively investigated over the past decades as a source for biofuel production due to their high lipid and carbohydrate yields, as well as being a natural source of high value-added bioactive compounds such as polyphenols, carotenoids, fatty acids, and antibiotics [1,2,3]
The magnetic particles were characterized by X-ray diffraction, identifying one predominant phase, namely that of magnetite, with a mean diameter size of 20 nm
The simple and rapid production route followed in this work leads to the formation of high purity nanocrystalline magnetite with a superparamagnetic behavior at room temperature

Summary

Introduction

Microalgae have been extensively investigated over the past decades as a source for biofuel production due to their high lipid and carbohydrate yields, as well as being a natural source of high value-added bioactive compounds such as polyphenols, carotenoids, fatty acids, and antibiotics [1,2,3]. In comparison to terrestrial crop plants, microalgae can provide higher productivity and photosynthetic performance, and since they can be cultivated on infertile land, they do not compete with existing food production methods [5,6]. Of the several major production steps of microalgae components, harvesting is both energy and time demanding. It is estimated that microalgae biomass harvesting is responsible for 20–30% of the total biomass production cost [7,8]. The harvesting step is crucial for the downstream process, since it leads to a slurry of highly concentrated solid matter [9]

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