A new mechanism for efficient hydrocarbon electro-extraction from Botryococcus braunii

Alexis Guionet,Justin Teissié,Hidenori Akiyama,Hamid Hosseini,Bahareh Hosseini

doi:10.1186/s13068-017-0724-1

Abstract

BackgroundRecent understanding that specific algae have high hydrocarbon production potential has attracted considerable attention. Botryococcus braunii is a microalga with an extracellular hydrocarbon matrix, which makes it an appropriate green energy source.ResultsThis study focuses on extracting oil from the microalgae matrix rather than the cells, eliminating the need for an excessive electric field to create electro-permeabilization. In such a way, technical limitations due to high extraction energy and cost can be overcome. Here, nanosecond pulsed electric fields (nsPEF) with 80 ns duration and 20–65 kV/cm electric fields were applied. To understand the extraction mechanism, the structure of the algae was accurately studied under fluorescence microscope; extraction was quantified using image analysis; quality of extraction was examined by thin-layer chromatography (TLC); and the cell/matrix separation was observed real-time under a microscope during nsPEF application. Furthermore, optimization was carried out by screening values of electric fields, pulse repetition frequencies, and energy spent.ConclusionsThe results offer a novel method applicable for fast and continues hydrocarbon extraction process at low energy cost.

Highlights

Recent understanding that specific algae have high hydrocarbon production potential has attracted considerable attention
There was a small unwanted spike of around 12% of maximal voltage at 0.9 μs after the pulse, which, under our experimental conditions, generated an electric field near 7.5 kV/cm, insufficient to have any impact on extraction
Fluorescence microscopy of Botryococcus braunii colony Protocol for fluorescence microscopy is described in the Additional file 1: Section 1-3)

Summary

Introduction

Recent understanding that specific algae have high hydrocarbon production potential has attracted considerable attention. Biodiesel from algae is a promising solution in the field of green energy. While energy derived from petroleum generates a huge carbon footprint, biodiesel generates an identical amount of carbon as is captured by the feed algae production [1]. While growing, algae captures carbon from atmospheric CO2 for diverse metabolic activity, especially hydrocarbon formation. All carbon used for fatty acid formation comes from atmospheric CO2, one reason why biodiesel has grown increasingly important in the new field of bioenergy. Biodiesel is generally derived from plant crops, Pulsed electric field (PEF) is anticipated as a promising method for hydrocarbon extraction from microalgae as it is able to permeabilize membranes and to weaken walls of cells [5,6,7,8]. Nanosecond pulsed electric fields (nsPEF) have been shown to be more energy efficient than millisecond or microsecond pulsed electric fields (msPEF or μsPEF); as nsPEF pulses are shorter, they

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