Cold water strain collection efforts.

Re-Distributed by http://www.tpub.com

National Renewable Energy Laboratory

temperature of 30EC or higher, except for PLEUR1 and THALA2, which had optimal

temperatures of 25EC and 28EC, respectively. Most of the strains grew well in a wide range of

salinities (e.g., five of the eight strains exhibited a growth rate greater than one doubling$day-1

at conductivities between 10 and 70 mmho@cm-1). With respect to the effect of water type on

growth, CHAET39, CYCLO4, and PLEUR1 grew best on SERI Type I medium. On the other

hand, CHAET6, CHAET9, and CHAET10 grew best in SERI Type II medium, but also exhibited

good growth on Type I medium and artificial seawater. CHAET15 and THALA2 achieved

maximal growth rates on artificial seawater, and, along with PLEUR1, grew very poorly on Type

II medium. These results again highlight the need to have a variety of algal strains available for

the specific water resources that would be available for mass culture in various locations.

The lipid contents of these 10 strains were also determined for exponentially growing cells, as

well as for cells that were grown under nutrient-limited conditions. Nitrogen deficiency led to an

increase in the lipid contents of CHAET6, CHAET9, CHAET10, CHAET15, CHAET39, and

PLEUR1. The mean lipid content of these strains increased from 11.2% (of the total organic

mass) in nutrient-sufficient cells to 22.7% after 4 days of N deficiency. Silicon deficiency led to

an increase in the lipid content of all strains (although in some cases the increase was small and

probably not statistically significant). The mean lipid content of the eight strains increased from

12.2% in nutrient-sufficient cells to 23.4% in Si-deficient cells. A few strains were poor lipid

producers, such as CHAET6, CYCLO4, and PLEUR1, which did not produce more than 20%

lipid under any growth conditions

Cold water strain collection efforts.

Most microalgal collection efforts carried out under the auspices of the ASP before 1987 focused

on sites that were expected to naturally experience high temperatures; indeed, one subcontractor,

Keith Cooksey (Montana State University) specifically searched for thermophilic strains isolated

from hot springs. This was because the temperatures of production ponds in the southwestern

United States during the prime growing season were expected to reach high levels; thus the

production strains would have to thrive under such conditions. However, temperatures in this

region are quite cool for several months of the year and can drop to below freezing at night.

Consequently, an effort was initiated by SERI researchers to collect, screen, and characterize

strains from cold-water habitats.

Four collecting trips were made between October 1986 and March 1987 to various inland saline

water sites in Utah and eastern Washington, and to the coastal lagoon waters in southern

California. Water samples were enriched with N, p, trace metals, and vitamins; artificial media

were not used in the initial selection protocol for these experiments. The rotary screening

apparatus was maintained at 15EC for the duration of the screening process by including a copper

cooling coil inside the screening chamber. The cultures were incubated for 5-10 days, which is

longer than for warm water strains because of the slower growth at the cooler temperature. This

procedure created a problem, however, in that many more strains survived the selection process

than when 30EC was used as the selection temperature. As a consequence, separating strains from

each other and identifying which were best for further characterization were more difficult.

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