Biocontainment of Genetically Engineered Algae

Environmental Applications of GM Microorganisms: Tiny Critters Posing Huge Challenges for Risk Assessment and Governance

In recent years, the interest in developing genetically modified microorganisms (GMMs), including GMMs developed by genome editing, for use in the environment has significantly increased. However, the scientific knowledge on the ecology of such GMMs is severely limited. There is also little experience at the hands of regulators on how to evaluate the environmental safety of GMMs and on how to assess whether they provide sustainable alternatives to current (agricultural) production systems. This review analyzes two different GMM applications, GM microalgae for biofuel production and nitrogen-fixing GM soil bacteria for use as biofertilizers. We assess the challenges posed by such GMMs for regulatory environmental risk assessment (ERA) against the background of the GMO legislation existing in the European Union (EU). Based on our analysis, we present recommendations for ERA and the monitoring of GMM applications, and in particular for the improvement of the existing EU guidance. We also explore whether existing approaches for technology assessment can provide a framework for the broader assessment of GMM applications. To this end, we recommend developing and implementing an evidence-based sustainability analysis and other methods of technology assessment to support decision making and to address broader societal concerns linked to the use of GMM applications in the environment.

Genetic Engineering for Cereal Crop Yield Improvement and Disease Resistant Breeding

Genetic engineering has revolutionized the field of agriculture, providing innovative solutions to enhance crop productivity and resilience against diseases. Among the various crops, cereals hold a pivotal position in global food security, feeding a significant portion of the world population. Genetic engineering, in cereal crop breeding, has opened new avenues for yield improvement and the development of disease-resistant varieties. Growing population and climate change, traditional breeding methods alone are insufficient to meet the increasing demand for food while ensuring sustainability. Genetic engineering offers a precise and efficient approach to introduce desirable traits into cereal crops, thereby improving yield and reducing the impact of diseases. One of the primary objectives of genetic engineering in cereal crops is to enhance yield potential. This can be achieved by modifying genes associated with key traits such as photosynthetic efficiency, stress tolerance, and nutrient use efficiency. For instance, genetic engineering can be used to increase the efficiency of light capture and conversion into biomass, thereby boosting yield. Disease resistance is another critical area where genetic engineering can make a significant impact. Pathogens and pests pose a constant threat to cereal crops, leading to significant yield losses. Genetic engineering techniques allow the introduction of genes encoding resistance to diseases, such as those from wild relatives or from other organisms. Here, evidence shows that the incorporation of Bacillus thuringiensis (Bt) genes into maize has effectively controlled corn borer infestations, reducing the need for chemical pesticides. This not only reduces yield losses but also minimizes the development of pathogen resistance to single-gene interventions.

Influence of Environmental Conditions on the Escape Rates of Biocontained Genetically Engineered Microbes

The development of genetically engineered microbes (GEMs) has resulted in an urgent need to control their persistence in the environment. The use of biocontainment such as kill switches is a critical approach to prevent the unintended proliferation of GEMs; however, the effectiveness of kill switches─reported as escape rates, i.e., the ratio of the number of viable microbes when the kill switch is triggered relative to the number when it is not triggered─is typically assessed under laboratory conditions that do not resemble environmental conditions under which biocontainment must perform. In this study, we discovered that the escape rate of an Escherichia coli GEM biocontained with a CRISPR-based kill switch triggered by anhydrotetracycline (aTc) increased by 3-4 orders of magnitude when deployed in natural surface waters as compared to rich laboratory media. We identified that environmental conditions (e.g., pH, nutrient levels) may contribute to elevated escape rates in multiple ways, including by altering the chemical speciation of the kill switch trigger to reduce its uptake and providing limited nutrients required for the kill switch to function. Our study demonstrated that conditions in the intended environment must be considered in order to design effective GEM biocontainment strategies.

Polyphosphate kinase deletion increases laboratory productivity in cyanobacteria

Identification and manipulation of cellular energy regulation mechanisms may be a strategy to increase productivity in photosynthetic organisms. This work tests the hypothesis that polyphosphate synthesis and degradation play a role in energy management by storing or dissipating energy in the form of ATP. A polyphosphate kinase (ppk) knock-out strain unable to synthesize polyphosphate was generated in the cyanobacterium Synechocystis sp. PCC 6803. This mutant strain demonstrated higher ATP levels and faster growth than the wildtype strain in high-carbon conditions and had a growth defect under multiple stress conditions. In a strain that combined ppk deletion with heterologous expression of ethylene-forming enzyme, higher ethylene productivity was observed than in the wildtype background. These results support the role of polyphosphate synthesis and degradation as an energy regulation mechanism and suggest that such mechanisms may be effective targets in biocontainment design.

Enzymatic Conversion of CO2: From Natural to Artificial Utilization

Enzymatic carbon dioxide fixation is one of the most important metabolic reactions as it allows the capture of inorganic carbon from the atmosphere and its conversion into organic biomass. However, due to the often unfavorable thermodynamics and the difficulties associated with the utilization of CO2, a gaseous substrate that is found in comparatively low concentrations in the atmosphere, such reactions remain challenging for biotechnological applications. Nature has tackled these problems by evolution of dedicated CO2-fixing enzymes, i.e., carboxylases, and embedding them in complex metabolic pathways. Biotechnology employs such carboxylating and decarboxylating enzymes for the carboxylation of aromatic and aliphatic substrates either by embedding them into more complex reaction cascades or by shifting the reaction equilibrium via reaction engineering. This review aims to provide an overview of natural CO2-fixing enzymes and their mechanistic similarities. We also discuss biocatalytic applications of carboxylases and decarboxylases for the synthesis of valuable products and provide a separate summary of strategies to improve the efficiency of such processes. We briefly summarize natural CO2 fixation pathways, provide a roadmap for the design and implementation of artificial carbon fixation pathways, and highlight examples of biocatalytic cascades involving carboxylases. Additionally, we suggest that biochemical utilization of reduced CO2 derivates, such as formate or methanol, represents a suitable alternative to direct use of CO2 and provide several examples. Our discussion closes with a techno-economic perspective on enzymatic CO2 fixation and its potential to reduce CO2 emissions.

Cyanobacteria as a Promising Alternative for Sustainable Environment: Synthesis of Biofuel and Biodegradable Plastics

With the aim to alleviate the increasing plastic burden and carbon footprint on Earth, the role of certain microbes that are capable of capturing and sequestering excess carbon dioxide (CO2) generated by various anthropogenic means was studied. Cyanobacteria, which are photosynthetic prokaryotes, are promising alternative for carbon sequestration as well as biofuel and bioplastic production because of their minimal growth requirements, higher efficiency of photosynthesis and growth rates, presence of considerable amounts of lipids in thylakoid membranes, and cosmopolitan nature. These microbes could prove beneficial to future generations in achieving sustainable environmental goals. Their role in the production of polyhydroxyalkanoates (PHAs) as a source of intracellular energy and carbon sink is being utilized for bioplastic production. PHAs have emerged as well-suited alternatives for conventional plastics and are a parallel competitor to petrochemical-based plastics. Although a lot of studies have been conducted where plants and crops are used as sources of energy and bioplastics, cyanobacteria have been reported to have a more efficient photosynthetic process strongly responsible for increased production with limited land input along with an acceptable cost. The biodiesel production from cyanobacteria is an unconventional choice for a sustainable future as it curtails toxic sulfur release and checks the addition of aromatic hydrocarbons having efficient oxygen content, with promising combustion potential, thus making them a better choice. Here, we aim at reporting the application of cyanobacteria for biofuel production and their competent biotechnological potential, along with achievements and constraints in its pathway toward commercial benefits. This review article also highlights the role of various cyanobacterial species that are a source of green and clean energy along with their high potential in the production of biodegradable plastics.