The effects of microalgal cell disruption via FeCl3-based synergistic effect between Fenton-like and Lewis acid reaction for lipid extraction

Lipid extraction from microalgae cell using persulfate-based oxidation

In this study, persulfate, a solid-type oxidant, was adopted as a substitute for hydrogen peroxide in extracting lipid from microalgae biomass. Microalgae cells were concentrated at pH 3 and with 200mg/L of ferric chloride, conditions which can activate oxidants such as hydrogen peroxide and persulfate. At a persulfate concentration of 2mM and a reaction temperature of 90°C, exceedingly high extraction efficiency over 95% was obtained, which was higher than with 0.5% hydrogen peroxide at the same temperature. This result showed that persulfate is sufficiently powerful and incomparably cheap enough to replace the potent yet expensive oxidant. It appears that combining iron-based coagulation and persulfate-based lipid extraction is indeed a competitive approach that can possibly lighten the process burden for the microalgae-derived biodiesel production.

Cell-wall disruption and lipid/astaxanthin extraction from microalgae: Chlorella and Haematococcus

Recently, biofuels and nutraceuticals produced from microalgae have emerged as major interests, resulting in intensive research of the microalgal biorefinery process. In this paper, recent developments in cell-wall disruption and extraction methods are reviewed, focusing on lipid and astaxanthin production from the biotechnologically important microalgae Chlorella and Haematococcus, respectively. As a common, critical bottleneck for recovery of intracellular components such as lipid and astaxanthin from these microalgae, the composition and structure of rigid, thick cell-walls were analyzed. Various chemical, physical, physico-chemical, and biological methods applied for cell-wall breakage and lipid/astaxanthin extraction from Chlorella and Haematococcus are discussed in detail and compared based on efficiency, energy consumption, type and dosage of solvent, biomass concentration and status (wet/dried), toxicity, scalability, and synergistic combinations. This report could serve as a useful guide to the implementation of practical downstream processes for recovery of valuable products from microalgae including Chlorella and Haematococcus.

Lipid extraction from microalgae cell using UV-Fenton-like reaction

In this study, UV light was adopted to make it possible to attain sufficiently high extraction efficiency even with a minimal amount of H2O2. The Fenton-like reaction showed 80% of lipid extraction efficiency with 0.5% H2O2, whereas the provision of 16 W UV increased efficiency to 85% and decreased H2O2 consumption to 0.3%. This oxidation-based lipid extraction means have one fortuitous yet beneficial effect to remove chlorophylls, which are known to degrade the quality of the final product like biodiesel. The UV-Fenton-like reaction was found to eliminate 77% of chlorophylls. Such oxidation-based lipid extraction approaches as the Fenton-like reaction appear to have the sure application potential; and it is more so with the help of UV.

An integrated process for microalgae harvesting and cell disruption by the use of ferric ions

In this study, a simultaneous process of harvesting biomass and extracting crude bio-oil was attempted from wet microalgae biomass using FeCl3 and Fe2(SO4)3 as both coagulant and cell-disrupting agent. A culture solution of Chlorella sp. KR-1 was firstly concentrated to 20 g/L and then proceeded for cell disruption with the addition of H2O2. Optimal dosage were 560 and 1060 mg/L for FeCl3 and Fe2(SO4)3, showing harvesting efficiencies of more than 99%. Optimal extraction conditions were identified via the response surface method (RSM), and the extraction yield was almost the same at 120 °C for both iron salts but FAME compositions after transesterification was found to be quite different. Given iron salts were a reference coagulant in water treatment in general and microalgae harvesting in particular, the present approach of using it for harvesting and oil-extraction in a simultaneous manner can serve as a practical route for the microalgae-derived biodiesel production.