DISRUPTION OF Nannochloropsis gaditana (EUSTIGMATOPHYCEAE) RIGID CELL WALL BY NON-THERMAL PLASMA PRIOR TO LIPID EXTRACTION AND ITS EFFECT ON FATTY ACID COMPOSITION

Ângelo P Matos,Anelise L V Cubas,Flávia M P S Corrêa,Marina S Teixeira,Elisa H S Moecke,Ernani S Sant’Anna,Marina M Machado,Ana C Aguiar,Rhuamm I S Werner

doi:10.1590/0104-6632.20190364s20190097

Abstract

Abstract This study assessed the effect of non-thermal plasma (NTP) on Nannochloropsis gaditana cell rupture and subsequent lipid extraction. Micrograph images showed that the surface of original N. gaditana cells appeared smooth and had no apparent holes, whereas after NTP the cells showed a non-uniform apparently fractured surface with many pores and large splits. Maximum lipid recovery from N. gaditana cells (~19%) for NTP-assisted rupture was observed at 10 min, similar to extraction after 10 min sonication (19.0%). The lipid recovery after both pretreatments (average 19.0%) was 2-fold higher than the control treatment (no pretreatment 9.5%). In addition, lipids from unruptured algal cells were mainly composed of ω-3polyunsaturated fatty acids (~31% of total fatty acids), while lipids after NTP were predominantly composed of saturated fatty acids (36.0% of total fatty acids), which could be advantageous for biodiesel production. This study demonstrates an alternative approach based on NTP-technology for algal cell rupture prior to lipid extraction with potential uses for algal biodiesel production.

Highlights

Microalgae have been identified by many researchers as a promising feedstock for biofuel production (Chisti, 2007; Phukan et al, 2011; Franz et al, 2013; Jazzar et al, 2015)
non-thermal plasma (NTP) is emerging as a promising biomass route to synthesize biofuels, such as bioethanol (Benoit et al, 2012; Delaux et al, 2016), and we have investigated the use of NTP for the production of biodiesel from waste frying oil, allowing fast reaction times and easy separation of the final product (Cubas et al, 2016; Istadi et al, 2009)
Since NTP has been proposed as a potential pretreatment for algal-lipid extraction, the aim of this experiment was to compare the lipid recovery from N. gaditana after NTP and after sonication treatments (Figure 2)

Summary

Introduction

Microalgae have been identified by many researchers as a promising feedstock for biofuel production (Chisti, 2007; Phukan et al, 2011; Franz et al, 2013; Jazzar et al, 2015). Several species of microalgae are able to accumulate carbohydrates and lipids which can be chemically converted into biofuels (Jazzar et al, 2015; Siqueira et al, 2016). According to Günerken et al (2015), the complete disruption of the algal cell wall prior to product recovery has been shown to be critical for successful process-scale lipid extraction from wet algal biomass. Feasible ways of extracting intracellular products are disruptions by physical, chemical or enzymatic methods to release the intracellular oil into the external medium (Mendes Pinto et al, 2001; Yap et al, 2015). A range of cell rupture techniques, including high pressure homogenization (Samarasinghe et al, 2012; Yap et al, 2015), ultrasonication (Lee et al, 2010; Halim et al, 2012), microwave heating (Lee et al, 2010; McMillan et al, 2013), bead milling (Postma et al, 2015) and osmotic shock (Lee et al, 2010) have been tested on algal suspensions and all have generally been shown to have a positive effect on lipid extraction

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