Adding glucose to a green microalga culture induces accumulation of fatty acids and other valuable bioproducts.
Algae can make dramatic shifts in their metabolism in response to changes in their environment. Some microscopic green algae stop photosynthesizing and start accumulating fats and other valuable molecules when certain changes happen. However, scientists don’t know the details of those swift metabolic changes. A team examined a green microalga to better understand this process. After a few days of feeding this microbe sugar, it completely dismantled its photosynthetic apparatus while accumulating fat. In contrast, after the team stopped feeding it sugar, the microbe returned to its normal metabolism.
Algae could be a sustainable source of biofuels and other valuable chemicals. As they trap carbon dioxide from the air by photosynthesis, they convert greenhouse gases into oils and other useful industrial products. Scientists need to know how algae control their metabolism to engineer strains that can make desirable products. This study showed that feeding glucose (sugar) to this alga affects one-third of its genes. This extensive catalog of affected genes opens the door to identify and manipulate critical genes that will dramatically increase oil production along with other tailored bioproducts.
Microalgae can produce large quantities of valuable oils and other chemicals, but their tight metabolic regulation poses a challenge for engineering these organisms for industrial-level production of biofuels and bioproducts. Using a variety of imaging and genomics technologies, a team from the University of California and national laboratories determined that only a few days after adding glucose to a culture of the green alga Chromochloris zofingiensis growing in the light, algal cells accumulate large amounts of the biofuel precursors triacylglycerols, as well as economically important products such as carotenoids. Further, they observed that photosynthesis shut off and the photosynthetic apparatus disappeared, while the overall culture biomass increased. At the same time, nearly one-third of the genes in the genome changed their expression during these growth and metabolic alterations. The researchers also discovered that these changes were readily reversed when they removed the glucose from the culture. Elucidation of the pathways that lead to high accumulation of those biofuels and bioproducts will allow scientists to engineer algae as sustainable biofactories.
U.S. Department of Energy Office of Science, Office of Biological and Environmental Research
Biological Systems Science Division (SC-23.2)
Foundational Genomics Research and Biosystems Design
University of California, Berkeley
Krishna K. Niyogi
University of California, Berkeley
This research was supported by the Office of Biological and Environmental Research within the U.S. Department of Energy (DOE) Office of Science. The authors acknowledge work performed by the DOE Joint Genome Institute (a DOE Office of Science user facility), the DOE Joint BioEnergy Institute, and the National Center for X-ray Tomography. The cryo-soft X-ray tomography was supported by the Photosynthetic Systems program in the Office of Basic Energy Sciences within the DOE Office of Science. The authors also acknowledge funding and support from the U.S. Department of Agriculture National Institute of Food and Agriculture, the National Institutes of Health, the National Science Foundation, and the Howard Hughes Medical Institute.
Roth, M. S., S. D. Gallaher, D. J. Westcott, et al. “Regulation of oxygenic photosynthesis during trophic transitions in the green alga Chromochloris zofingiensis.” The Plant Cell 31, 579–601 (2019). [DOI:10.1105/tpc.18.00742].
University of California, Los Angeles news release: Discovery of an alga’s ‘dictionary of genes’ could lead to advances in biofuels, medicine
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