Harvesting of Chlorella sorokiniana BR001 cultivated in a low-nitrogen medium using different techniques

Rafael De Araújo Lira,Antonio Teixeira De Matos,Mariana Machado Rocha,Jane Selia Dos Reis Coimbra,Jimmy Soares,Marcio Arêdes Martins,Lucas De Paula Corrêdo

doi:10.1590/0103-8478cr20200293

Rafael De Araújo Lira, Antonio Teixeira De Matos + Show 5 more

Open Access

https://doi.org/10.1590/0103-8478cr20200293

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Journal: Ciência Rural	Publication Date: Jan 1, 2022
License type: CC BY 4.0

Affiliation: Universidade Federal de Viçosa

Abstract

ABSTRACT: The harvesting process is a current challenge for the commercial production of microalgae because the biomass is diluted in the culture medium. Several methods have been proposed to harvest microalgae cells, but there is not a consensus about the optimum method for such application. Herein, the methods based on sedimentation, flocculation, and centrifugation were evaluated on the recovery of Chlorella sorokiniana BR001 cultivated in a low-nitrogen medium. C. sorokiniana BR001 was cultivated using a low-nitrogen medium to trigger the accumulation of neutral lipids and neutral carbohydrates. The biomass of C. sorokiniana BR001 cultivated in a low-nitrogen medium showed a total lipid content of 1.9 times higher (23.8 ± 4.5%) when compared to the biomass produced in a high-nitrogen medium (12.3 ± 1.2%). In addition, the biomass of the BR001 strain cultivated in a low-nitrogen medium showed a high content of neutral carbohydrates (52.1 ± 1.5%). The natural sedimentation-based process was evaluated using a sedimentation column, and it was concluded that C. sorokiniana BR001 is a non-flocculent strain. Therefore, it was evaluated the effect of different concentrations of ferric sulfate (0.005 to 1 g L-1) or aluminum sulfate (0.025 to 0.83 g L-1) on the flocculation process of C. sorokiniana BR001, but high doses of flocculant agents were required for an efficient harvest of biomass. It was evaluated the centrifugation at low speed (300 to 3,000 g) as well, and it was possible to conclude that this process was the most adequate to harvest the non-flocculent strain C. sorokiniana BR001.

Highlights

Harvesting of microalgal biomass is considered a bottleneck in algae farms because the biomass is generally diluted in the medium (0.5 to 4 kg of dry weight per m-3), and many microalgae with biotechnological potential are planktonic organisms that show density values similar to water (TIRON et al, 2017)
The strain C. sorokiniana BR001 cultivated in a low-nitrogen medium showed a content of total lipids 1.9 times higher (23.8 ± 4.5% in dry weight basis, DW) when compared to the cultivation with a rich-nitrogen medium (12.3 ± 1.2% DW)
The sedimentation process was slow and inefficient to harvest the C. sorokiniana BR001 biomass, and it was possible to recover only 30% of the biomass after 350 min (Figure 1A). These results clearly show that C. sorokiniana BR001 is not a self-flocculent strain

Summary

Introduction

Harvesting of microalgal biomass is considered a bottleneck in algae farms because the biomass is generally diluted in the medium (0.5 to 4 kg of dry weight per m-3), and many microalgae with biotechnological potential are planktonic (i.e. free-floating) organisms that show density values similar to water (TIRON et al, 2017). Harvesting of microalgae biomass requires costly and complex processes that can reach up to 30% of the total costs of production (FASAEI et al, 2018). Sedimentation shows low operational costs when compared to other methods of biomass harvest (FASAEI et al, 2018), but the slowness of this process may be a problem for microalgae with a fast metabolism. Catabolism reactions may occur during the harvest process leading to undesired changes in the biochemical composition of the microalgae before their extraction

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