By Cara Burke
The need for renewable and sustainable fuels is growing more and more urgent as the current climate crisis continues to worsen. Fossil fuels which contribute to the ever-growing rise of greenhouse gas emissions are not only continuing to be used but used to such extent that they are running out. A possible and tempting alternative? Biofuels.
Biofuels are fuels produced from organic material such as animal or plant waste. First-generation biofuels, which use food-crops as raw materials, have serious disadvantages as it encourages land use to grow crops for biofuel rather than food. Food shortages and deforestation can often be the result, as seen in countries in South America and Southeast Asia.
Second-generation biofuels, on the other hand, are produced from non-food crops, primarily those with high lignocellulose content (the complex of cellulose and lignin that is present in the cell walls of particularly woody plants). One of their big advantages is that they can be produced from agricultural or industrial waste products. They are, therefore, much better in terms of their environmental impact than first-generation biofuels.
Third-generation biofuels have the potential to be even better for the environment. These biofuels are produced directly from microorganisms, and particularly from green algae (Chlorophyceae), which produce fatty lipids in their dormant phase.
There is still a lot of progress to be made when it comes to making and using biofuels in an efficient and environmentally friendly way. Thankfully, CRISPR-Cas9 has allowed for huge advances to be made in biofuel production. Enzymes produced by bacteria, algae and fungi are used in every step and gene editing is very useful tool in biofuel production. It allows these organisms to be hardier against the antimicrobial products of biofuel production and to produce more of the enzymes essential to the biofuel manufacturing process. Most organisms used in biofuel production processes have been genetically modified in some way. What’s new is how much quicker and easier modifying these organisms becomes with CRISPR-Cas9.
The most recent exciting CRISPR-Cas9 development for biofuels has come from a group of researchers in Brazil who genetically engineered the fungi Trichoderma reesei to produce a cocktail of enzymes that effectively break down carbohydrates into second-generation ethanol. T. reesei already accounts for up to 80% of the enzyme formulations that are used to break down lignocellulosic materials in the biofuels industry. CRISPR-Cas9 was used to increase the effectiveness of the enzymes produced by the fungus, the enzyme’s secretion rate, and the survival rate of that fungus on a cheaper carbon source (sucrose-rich molasses). They were able to produce 80 grams of enzymes per litre, double of what this fungus was previously reported to produce. This is an important improvement since culture medium components account for around 60% of enzyme production costs. Modifying the fungus to grow on a cheaper medium creates a much more cost-effective way of producing biofuels. This is particularly exciting in Brazil, where the sugar cane industry produces 70 million metric tons of waste every year that could be used to produce useful fuels.
CRISPR-Cas9 is also proving to be very useful in the modification of algae for third-generation biofuels. Photosynthetic microalgae can fix carbon, providing us with the opportunity to produce carbon-neutral biofuels, the need for which is increasingly growing. In 2017, CRISPR was used to double the rate at which a certain strain of microalgae produces lipids, without affecting the growth rate of the algae itself. Whilst this is an exciting development there is a lot more to be done for microalgae to be a good source of biofuel. Their growth can be limited, especially the highest lipid producing strains, and need specific conditions to produce lipids in the levels required for effective biofuel production. A better understanding of lipid synthesis and its regulation in microalgae will allow CRISPR-Cas9 to be used as an effective tool for modifying algae to effectively produce biofuels.
Genetic engineering, particularly using CRISPR-Cas9, has been very effective in improving the way we produce biofuels and offers so many more opportunities for better biofuel production in the future. Genetically engineered organisms required decades of research in the past and various methods to form new, useful strains. CRISPR-Cas9 allows us to modify organisms a lot quicker and publicly available strains of organisms can be used, making this technology of innovate biofuel production more accessible. It has shown huge promises for the modification of organisms in efficient biofuels production, and we are already starting to see the very exciting results.