Researchers at Los Alamos National Laboratory, with colleagues at NREL and the University of Georgia report that a freshwater production strain of microalgae, Auxenochlorella protothecoides UTEX 25, is capable of directly degrading and utilizing non-food plant substrates, such as switchgrass, for cell growth. In addition, the use of plant substrates increases lipids production.

The researchers suggest that utilization of plant-based carbon substrates in addition to photosynthesis (mixotrophic growth) for biochemical assimilation into biomass, biofuels, and bioproducts, can increase cultivation productivity and improve the economic viability of algal-derived biofuels. Their open-access paper appears in the journal Algal Research.

Algae hold great potential as a source of renewable fuel due to their ability to produce refinery-compatible diesel and jet fuel precursors. Identifying algae strains that can use plant substrates, such as switchgrass and corn stover (the part of the plant left in a field after harvest) to grow faster and with more lipids suggests that waste plant material can be used to increase the productivity of algae during cultivation for biofuels or bioproducts.

Pinpointing the unique enzymes and biochemical pathways algae use to break down complex plant lignocellulose increases our understanding of algal biology, and it opens up new avenues of future designer engineering to improve algal biofuel production strains.

—Amanda Barry of Los Alamos’ Bioenergy and Biome Sciences group, corresponding author

The study presents the first example of algae degradation and utilization of untreated plant substrate, the putative genetic and molecular mechanisms behind this degradation, and identifies potential glycosyl hydrolases that may be involved in plant deconstruction.

This research identifies potential gene targets for future genetic engineering of plant substrate degradation and calls attention to the potential benefits of growing algae with plant substrate at larger scales to generate greater algae biomass and lipid production.

—Vogler et al.

This work was partly supported by a grant from the Laboratory Directed Research and Development Early Career Research Program at Los Alamos National Laboratory and funds provided by the US Department of Energy’s Bioenergy Technologies Office.

Resources

• Brian W. Vogler, Shawn R. Starkenburg, Nilusha Sudasinghe, Jenna Y. Schambach, Joseph A. Rollin, Sivakumar Pattathil and Amanda N. Barry (2018) “Characterization of plant carbon substrate utilization by Auxenochlorella protothecoides” Algal Research 34C pp. 37-48 doi: 10.1016/j.algal.2018.07.001