5.4.1 Small Molecules

The microalga Dunaliella salina can contain up to 40% of its dry weight as glycerol. However, the low price of glycerol (as a coproduct of biodiesel production) means that the algal product would not be competitive. Other algal species accumulate high concentrations of proline under conditions of high salinity (Benemann and Oswald 1996).

Although a number of algal strains were investigated for growth and lipid pro­duction properties, the best candidates were found in two classes, Chlorophyceae (green algae) and Bacilliarophyceae (diatoms). Organisms were identified in both classes that showed high productivity, an ability to grow in large-scale culture, and lipid accumulation upon nutrient stress. However, in some ways the diatoms may turn out to be better candidate organisms for biofuel production.

A dozen potential by — and coproducts can be obtained from algae. These are io­dine, algin, mannitol, and lignin-related fraction, the first three being commercial products. The lignin-related fraction was suggested as a feedstock or as a compo­nent for making specialty plastics, adhesives, and timed-release substances such as pharmaceuticals or pesticides (Chynoweth et al. 1993).