The collection and screening effort resulted in a large number of strains that had many characteristics deemed important for a biodiesel production organism. In reviewing the many procedures used by ASP researchers, however, it is clear that a more consistent screening protocol might have yielded results that could be compared more meaningfully. Although these types of standard protocols were being developed near the end of the collection and screening effort, they were not consistently used. Furthermore, because an optimized microalgal-based biofuel production process was never fully developed, the screening protocols could not be based on an actual process. Therefore, whether the screening criteria used in the ASP were accurate predictors of good performance in a biodiesel production facility is not really known. For example, lipid productivity over a given amount of time is one of the most important factors in a production process. There were no clear guidelines as to whether lipid productivity in an outdoor pond was better in a continuous, steady-state process or in a multistage process involving substantial culture manipulation (e. g., nutrient level control, “ripening” tanks). This information is critical, and has a profound impact on the type of screening that should be conducted.

In addition to the need for a better understanding of the most economically feasible commercial biodiesel production process, additional information about the true constraints with regard to lipid properties (e. g., fatty acid chain length, degree of unsaturation, polar lipid constituents, etc.) there is a need for better information on the impact of lipid composition on fuel quality. The lipophilic dye Nile Red was used as a screening tool to rapidly assess the lipid contents of isolates, but in retrospect this technique probably does not provide the level of detail regarding lipid quality that may be necessary. Indeed, the variability in the ability of various strains to take up this dye is a major problem that must be recognized. With the rapid advances that have been made in recent years in automated high performance liquid chromatography and detection, this technique seems readily adaptable for use as a powerful screening tool.

For future screening endeavors, we recommend that an effort be made to naturally select strains at the locations that would likely be commercial microalgal production sites. In this manner, the algae would be exposed to the prevailing environmental conditions, particularly the indigenous waters. In small open-air vessels, the medium would be “inoculated” with a variety of indigenous strains, and a process of natural selection would occur such that the most competitive strains would dominate the cultures after a short while. Of course, the disadvantage of this method is that the dominant strains may not be good lipid producers. For this reason, genetically manipulating the dominant strains by classical or recombinant means may be necessary, such that they remain competitive and yet make acceptable amounts of lipid. Whether such manipulations can be made awaits further experimentation.

One thing that was clear from the collection and screening effort was that diatoms and green algae would most likely be well represented in a “natural selection” screen as described in the preceding paragraph. Therefore, future efforts should probably focus on developing sophisticated genetic engineering tools focused on these groups. Such tools could be transferable to many different species within these groups; such transfer would be facilitated by the fact that powerful methods for generating genetic sequence information are becoming routine.