Algae are made up of prokaryatic as well as eukaryotic cells. These are cells with nuclei and organelles. All algae have plastids, the bodies with chlorophyll that carry out photosynthesis. But the various lines of algae have different combinations of chlorophyll molecules. Some have only Chlorophyll A, some A and B, while other lines, A and C.

All algae primary comprise of the following, in varying proportions: Proteins, Carbohydrates, Fats and Nucleic Acids. While the percentages vary with the type of algae, there are algae types that are comprised up to 40% of their overall mass by fatty acids. It is this fatty acid (oil) that can be extracted and converted into biodiesel.

Table 1 - Chemical Composition of Algae Expressed on A Dry Matter Basis (%)

Source: Becker, (1994) 

Algal-oil is very high in unsaturated fatty acids. Some UFA's found in different algal-species include:

• Arachidonic acid(AA)
• Eicospentaenoic acid(EPA)
• Docasahexaenoic acid(DHA)
• Gamma-linolenic acid(GLA)
• Linoleic acid(LA)
  

The interest in algal oil is not new, though the widespread interest in making Biodiesel from algal oil is more recent. Algae oil has been produced and used for the cosmetic industry, primarily from macroalgae (larger sized algae) such as oarleaf Seaweed etc. Most current research on oil extraction from algae is however focused on microalgae.

See also:

• Lipid Content of Algae – Biodiesel Now Forums
• SERI Microalgae Culture Collection - Wikipedia
• Preliminary Report of Distribution of Aliphatic Hydrocarbons in Algae & Bacteria (PDF)
• Chemical Constituents of Marine Algae off Karachi Coast (PDF)
• Marine Micro-algae as a Source of Omega-3 Fatty Acids
  

More articles & news on algal chemical composition: Visitors may kindly have a look at the Oilgae Blog Directory for relevant blog articles.

Reference: Chemistry & Structure of Fixed Oils

Fixed oils from seeds, nuts & vegetables are typically composed of triglyceride molecules (also known as triacylglycerol or triacylglyceride). A triglyceride is a glyceride in which the glycerol is esterified with three fatty acids - a triglyceride is typically composed of a 3-carbon alcohol (glycerol) plus three 18-carbon (or 16-carbon) fatty acids. The 18-carbon fatty acids are Linoleic acid, Stearic acid & Oleic acid.

• Glycerol + Three Fatty Acids = A Fat Molecule (Triglyceride)
• Linoleic Acid Polyunsaturated: 2 Double Bonds In The Molecule
• Stearic Acid Saturated: All Single Bonds Between Atoms Of Carbon
• Oleic Acid Monounsaturated:1 Double bond between Carbon 9 & 10
  

The fatty acids may be saturated (with all single bonds), mono-unsaturated (with one double bond) or polyunsaturated (with 2 or more double bonds). Plant fatty acids are usually unsaturated and liquid at room temperature, with one or more double bonds between the carbon atoms (mono-unsaturated and polyunsaturated). A notable exception is the palm fatty acid – palmitin – which is saturated and contains 16 rather than 18 carbon atoms. Since the plant fatty acids are unsaturated, the plant oils it is liquid at room temperature.

See also: Triglycerides – from Wikipedia, Linoleic Acid – from Wikipedia, Stearic Acid – from Wikipedia, Oleic Acid Physical & Chemical Properties, Fats, Oils, Fatty Acids, Triglycerides Chemical Structure, See also: Food, Fats & Oils – from ISEO (PDF), Determining the Contents of Oilseeds (PDF)

Cis & Trans Fatty Acids

Fatty acid isomers containing double bonds may have the cis or trans configuration. In cis fatty acids, all the hygrogen atoms adjacent to the double bonds are on the same side of the longitudinal carbon axis. In trans fatty acids, the hygrogen atoms adjacent to the double bonds occur on alternate sides of the main axis.

The trans configuration is chemically more stable. It is typically produced during partial hydrogenation of polyunsaturated vegetable oils.

Trans fatty acids tend to raise the level of low density lipoproteins (LDLs = bad) and lower the level of high density lipoproteins (HDLs = good). These changes in blood Lipids (cholesterol levels) may increase the risk of heart disease (atherosclerosis) in some people. Dieticians generally recommend the use of mono-unsaturated, unhydrogenated oils and the avoidance of trans fatty acids found in french fries, cookies and crackers.

Unsaturated fatty acids found in plant oils and seeds are typically Omega-6 Fatty Acids in which the first double bond is located on the sixth carbon atom, counting backwards from right to left. Omega-3 fatty acids – in which the first double bond in on carbon #3 - are prevalent in fish oils and flax seeds.

• Chemical & Nutritional Properties of Olive Oil – Olive Oil Source
• Algae – New Source of Omega-3 Fats
• Trans Fatty Acids – from American Heart Association
• The Influence of Trans Fatty Acids on Health (PDF)
• Trans Fatty Acids & Coronary Heart Disease – Harvard School of Public Health
  

Other Related Sections

Blue Green Algae, Red Algae, Green Algae, Marine Algae, String Algae, Pond Algae, Pond Algae Control, Algae Control