Laboratory Studies

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National Renewable Energy Laboratory

II.

Laboratory Studies

II.A.

Collection, Screening, and Characterization of Microalgae

II.A.1.

Collection, Screening, and Characterization of Microalgae by SERI In-House

Researchers

II.A.1.a.

Introduction

This chapter describes the research performed at SERI in the area of microalgal collection and

screening. In addition to performing actual research in this area, SERI personnel were responsible

for coordinating the efforts of the many subcontractors performing similar activities, and for

standardizing certain procedures and analyses. These efforts ultimately resulted in the

development of the SERI Microalgal Culture Collection, which is more fully described in Chapter

II.A.3.

Brief review of algal taxonomic groups and characteristics:

For the purposes of this report, microalgae are defined as microscopic organisms that can grow

via photosynthesis. Many microalgae grow quite rapidly, and are considerably more productive

than land plants and macroalgae (seaweeds). Microalgae reproduction occurs primarily by

vegetative (asexual) cell division, although sexual reproduction can occur in many species under

certain growth conditions.

There are several main groups of microalgae, which differ primarily in pigment composition,

biochemical constituents, ultrastucture, and life cycle. Five groups were of primary importance

to the ASP: diatoms (Class Bacillariophyceae), green algae (Class Chlorophyceae), golden-brown

algae (Class Chrysophyceae), prymnesiophytes (Class Prymnesiophyceae), and the

eustigmatophytes (Class Eustigmatophyceae). The blue-green algae, or cyanobacteria (Class

Cyanophyceae), were also represented in some of the collections. A brief description of these

algal groups follows.

Diatoms. Diatoms are among the most common and widely distributed

groups of algae in existence; about 100,000 species are known. This group

tends to dominate the phytoplankton of the oceans, but is commonly found

in fresh- and brackish water habitats as well. The cells are golden-brown

because of the presence of high levels of fucoxanthin, a photosynthetic

accessory pigment. Several other xanthophylls are present at lower levels,

as well as β-carotene, chlorophyll a and chlorophyll c. The main storage

compounds of diatoms are lipids (TAGs) and a β-1,3-linked carbohydrate

known as chrysolaminarin. A distinguishing feature of diatoms is the

presence of a cell wall that contains substantial quantities of polymerized Si.

A Look Back at the Aquatic Species Program--Technical Review