ABSTRACT
This chapter discusses the four main types of microorganisms that are used for the production of biodiesel: bacteria, yeast, fungi, and microalgae. Oleaginous microorganisms, that is, yeast, filamentous fungi, and microalgal species, are very interesting organisms that are able to accumulate lipids at levels greater than 20" of their cellular dry weight. Microorganisms have long been used in industrial processes, starting with alcohol fermentation using Saccharomyces cerevisiae. Microalgae are rich in some products, such as pigments and chlorophyll, which make them particularly attractive for other applications, like cosmetics, pharmaceuticals, and food. Microalgae can be classified into four main classes: diatoms, green algae, blue-green algae, and golden algae. Single-cell oils are lipids that are extracted from unicellular microorganisms. The oil extraction and purification of single cell oils still represent major costs in the production process. It is therefore important to have efficient downstream processing.
