Evaluation of phenotype stability and ecological risk of a genetically engineered alga in open pond production

Abstract

A B S T R A C TGenetically engineered (GE) algae offer the promise of producing food, fuel, and other valuable products with reduced requirements for land and fresh water. While the gains in productivity measured in GE terrestrial crops are predicted to be mirrored in GE algae, the stability of phenotypes and ecological risks posed by GE algae in large-scale outdoor cultivation remain unknown. Here, we describe the first US Environmental Protection Agency (EPA)-sanctioned experiment aimed at understanding how GE algae perform in outdoor cultivation. Acutodesmus dimorphus was genetically engineered by the addition of two genes, one for enhanced fatty acid biosynthesis, and one for recombinant green fluorescence protein (GFP) expression; both the genes and their associated phenotypes were maintained during fifty days of outdoor cultivation. We also observed that while the GE algae dispersed from the cultivation ponds, colonization of the trap ponds by the GE strain declined rapidly with increasing distance from the source cultivation ponds. In contrast, many species of indigenous algae were found in every trap pond within a few days of starting the experiment. When inoculated in water from five local lakes, the GE algae's effect on biodiversity, species composition, and biomass of native algae was indiscernible from those of the wild-type (wt) progenitor algae, and neither the GE nor wt algae were able to outcompete native strains. We conclude that GE algae can be successfully cultivated outdoors while maintaining GE traits, and that for the specific GE algal strain tested here they did not outcompete or adversely impact native algae populations when grown in water taken from local lakes. This study provides an initial evaluation of GE algae in outdoor cultivation and a framework to evaluate GE algae risks associated with outdoor GE algae production.

Metabolic engineering of phosphite metabolism in Synechococcus elongatus PCC 7942 as an effective measure to control biological contaminants in outdoor raceway ponds

“…In addition to phenotype stability in outdoor conditions, the ecological risk due potential accidental environmental releases of genetically engineered microalgae/cyanobacteria has emerged as a major concern during large-scale cultivation [54,55]. Evaluation in open pond production systems represent a crucial step in understanding potential ecological risk of genetically engineered cyanobacteria/microalgae.…”

Emerging Technologies in Algal Biotechnology: Toward the Establishment of a Sustainable, Algae-Based Bioeconomy

“…While there are currently limited studies on genetic engineering of microalgae for bioremediation purposes, Chiaiese et al (2011) successfully demonstrated fungal laccase POX A1b expression in the green alga, Chlorella emersonii, which enhanced microalgal biodegradation of phenols by up to about 40%. However, while genetically engineering microalgae for enhanced biodegradation appears promising, the potential environmental risks intrinsic to the use of genetically modified organisms (GMO) that would limits their application in outdoors settings need to be evaluated (Szyjka et al, 2017). In addition to this, for many countries, the legislation around the limited use, or the total ban of, GMOs means that transgenic microalgae for ECs biodegradation would not be a viable option, at present.…”

Gene Editing of Microalgae: Scientific Progress and Regulatory Challenges in Europe

“…EFSA reviewed this area and commented as follows: “According to our experience, the current European legislative framework for GMOs and for food/feed products of microbial origin (whether they are GM or not) would cover GM microalgae sufficiently.” Regardless of the category of organism, the regulations considered herein relate to GMOs broadly and would include both GMMs and GM Plants. With regard to production of GM algae beyond labscale, contained use—often double-contained or restricted-access greenhouse—is considered to be a safe working model at the current time, although outdoor trials have gone ahead and have been reported in the USA [ 29 ].…”