Desikan Ramesh

Department of Farm Machinery

Agricultural Engineering College and Research Institute Tamil Nadu Agricultural University Coimbatore, Tamil Nadu, India

CONTENTS

7.1 Lipid Quantification……………………………………………………………………………………. 89

7.2 Lipid Profiles……………………………………………………………………………………………….. 90

7.2.1 Identification of Algae Lipid Profiles…………………………………………….. 90

7.2.2 Suitability of Algae Lipid for Biodiesel Production………………………… 90

7.3 Oil Extraction………………………………………………………………………………………………. 92

7.3.1 Mechanical Extraction………………………………………………………………….. 92

7.3.1.1 Oil Expeller………………………………………………………………………. 93

7.3.2 Chemical Extraction……………………………………………………………………… 93

7.3.2.1 Solvent Extraction………………………………………………………….. 93

7.3.2.2 Supercritical Fluid Extraction (SFE)………………………………… 94

7.4 Conclusion………………………………………………………………………………………………….. 95

References…………………………………………………………………………………………………………… 96

7.1 LIPID QUANTIFICATION

Due to their high oil content, microalgae have attracted substantial research atten­tion for biodiesel production and furthermore, algae have the capability to replace conventional biodiesel feedstocks. Algal strains collected from diverse aquatic environments require the evaluation of various important parameters such as oil content, lipid composition, growth rate, and metabolic efficiency under different conditions. One can decide whether the selected algal strain is suitable/unsuitable for biodiesel production based on the preliminary lipid analysis (both lipid yield and lipid composition).

Microalgal strains have the potential to produce up to 50% lipid by dry cell weight, depending on the species and specific growth conditions (Chisti, 2007). The neutral lipids present in microalgae are primarily in the form of triacylglycerols (TAGs). TAGs can be converted to fatty acid methyl esters (FAMEs) via transesterification. Recovery of the accumulated algae lipids from algae paste is generally carried out after rupturing the cells to free the lipids. Different cell disruption techniques are used to rupture the algae cells, including autoclaving, microwave, sonication, osmotic shock, and bead beating. Lee et al. (2010) evaluated five different cell disruption techniques for enhancing lipid extraction efficiency. They reported that the micro­wave oven method is an efficient method for extracting lipids from microalgae. Because of its simplicity and cost effectiveness, solvent extraction is widely used by researchers (Letellier and Budzinski, 1999). For laboratory-scale studies, lipid con­tent and composition can be determined using well-established techniques. The most commonly used method for lipid extraction is the Bligh and Dyer method, or some variation thereof. Methods for simultaneous extraction and transesterification of algal biomass to extract the algal lipids are also available (Belarbi et al., 2000; Lewis et al., 2000).