Reviewer Comments - EERE

2011 Algae Platform Review – Reviewer Comments
Reviewer Comments are direct transcripts of commentary and material provided by the Platform’s
Review Panel. They have not been edited or altered by the Biomass Program.
Reviewer: 4 Criteria Score: 2
For lemna to be a useful biofuel crop, it must have high biomass and/or oil productivity under mass
cultivation conditions. The presenter stated that his projections of high biomass productivity stem from
commercial sources. These may not be reliable. For example, low productivity (~4 g/m2-d) was measured
by Ryer in the 1970s. A literature review on lemna productivity should be a high priority.
What is the potential to genetically manipulate lemna to have high lipid productivity if they are a
naturally low productivity organism? Are the lemna production facility designs technically and
economically feasible. This is presumably not the expertise of the presenter, who is a biologist, but since
the stated goal of the project is to create a biofuel crop, these techno-economic matters must be addressed.
The statement "Lemna spp. are already in widespread commercial use for animal feed and bioremediation
of waste water" is an exaggeration. There may be a handful of sites in existence. Lemna Corp. was not
very successful in commercializing lemna wastewater treatment in the 1990s.
Reviewer: 5 Criteria Score: 3
The objective is to increase oil content of duckweed. The approach is genetic: genome sequencing of
lemna, followed by development of transformation and expression system in duckweed. Although the
science is sound, the presenter did not convey any understanding of the larger picture (use and value of
duckweed production systems). This lack of understanding unnecessarily limits the value of this research.
Reviewer: 7 Criteria Score: 3
Independent varification of growth rate claims should be made before research work is initiated.
Presenter Response
We apologize for not giving a longer introduction to the considerable research already published
concerning the enormous growth and yield potential of duckweed and other aquatic plants as biofuel
feedstocks. The Ryan study is generally considered an outlier in these studies. Geographic distributions of
each species were determined by Elias Landolt in amassing a live culture collection of 1300 isolates. The
phytochemical composition of the Lemnaoideae, including carbohydrate, lipid, and protein content, has
been studied since the early 20th century. Cheng and Stomp (2009) provide a good survey of potential
commercialization avenues for duckweed aquaculture, including promising data on efficient starch
production. Duckweed may constitute an excellent feedstock for ethanol biofuels, yet this does not
diminish the value of investigating the potential for lipid production in the plant, as the demand for lipidbased
biofuels remains. Cheng and Stomp (2009):
http://www.mekarn.org/MSc_CTU/literature/cheng%20et%20al%202009.pdf We recommend the
following white paper as a source of reviews:
http://lemna.rutgers.edu/Michael_duckweed_JGIDOE_2008_final.pdf This white paper forms the basis
for the S.polyrhiza genome sequencing program at the DOE JGI genome sequencing center. As described
during our presentation, our program will build on this reference genome sequence, first by sequencing
several other genera that have superior potential as biofuels (eg. Oil content, geographical range, genetic
properties). We have begun with Lemna gibba, described in the presentation. With respect to progress in
our research proposal, preliminary analysis of TAG content in several accessions of S. polyrhiza was
presented in additional slides at the end of the presentation. However, new technology developed over the
last decade has made genomics a powerful alternative to classical physiological analysis of lipid and other
feedstock composition. As we described in the presentation, the gene catalog will form the foundation for
a model of carbon paritioning that can be further tested in a more diected way. By analogy, the genome of
microalgae and diatoms has proven to be an essential component of biofuel strategies seeking to increase
lipid content. We learned at the review meeting that lipid content is the limiting factor in energy balance
and so we have made it the focus of our project. We have already made substantial progress in stable
Page 194 of 223