Advanced BioFuels USA – To Fulfill Biofuels’ Promise, Scientists Boost Plant Oils with Gene Editing

by Cici Zhang (Chemical and Engineering News) Increasing the fatty acids in crops’ seeds, leaves, and stems could make biofuels more economically viable -- ... Plant scientist Heike Sederoff of North Carolina State University, however, is very familiar with the oils that camelina offers. The highly concentrated fatty acids produced by the flaxlike plant are sought for their ability to be converted into biofuel, which Sederoff studies. Camelina seeds, in fact, have already been used to manufacture commercial jet biofuel.

Despite how environmentally friendly it sounds to use plants like camelina to make biofuels for transportation needs, how to do it in a cost-effective and sustainable way has been an issue.

Some studies suggest that the use of biofuels could reduce greenhouse gas emissions by 60 to 94% relative to fossil fuels (Agriculture 2017, DOI: 10.3390/agriculture7040032). ...

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One avenue of innovation being pursued by Sederoff and others is to genetically tinker with plants like camelina to either boost their oil production or reduce the chain length of the fatty acids they generate, diminishing the energy that refineries have to use to convert those compounds into usable fuels. These actions, the scientists hope, would make biofuels more economically viable.

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Even with funding in hand, however, scientists who are genetically engineering crops to increase biofuels’ profitability could face a big roadblock. Skepticism over gene-edited crops has led to stringent regulations in the European Union: A July 25 ruling will make it difficult for scientists to conduct field trials in EU countries and to bring gene-edited products to the European market.

In the U.S., though, the Department of Agriculture says it is not going to regulate gene-edited crops that could otherwise be produced by conventional breeding methods, as long as the crop isn’t edited to include a plant-pest-derived DNA sequence. According to Neil Hoffman, a scientific adviser at USDA’s Animal & Plant Health Inspection Service (APHIS), USDA would be more likely to regulate a gene-edited crop if it were considered a plant pest or weed and would harm other plants if the gene-edited version spread into the environment.

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For example, if someone engineered switchgrass, a weedy plant that can be converted to biofuel, to have improved drought tolerance, would a serious weed problem occur?

“We don’t believe that genetically engineered organisms need to be regulated” just because they are genetically engineered, Hoffman says. Researchers and companies planning to release a gene-edited crop into the environment can go through a process called “Am I Regulated?” to identify whether their products need to apply for a permit from USDA.

A recent gene-edited plant that received APHIS’s nonregulated status is a camelina plant from Yield10 Bioscience, a biotech company that hopes to improve plant oil production and oil quality.

Oliver Peoples, Yield10’s CEO, tells C&EN the company is planning on field trials for this camelina line in 2019. Having the plant identified as nonregulated by USDA definitely accelerated the process for the firm to pursue development in a cost-effective way, Peoples says.

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If the current techniques work well in camelina, the company will attempt similar gene edits in canola and soybeans.

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Recognizing the need to streamline processing steps and reduce cost in biofuel manufacturing, Sederoff is also working to engineer camelina to produce oil that requires less energy to convert it into biodiesel.

When plants take in carbon dioxide and then “fix” the molecule’s carbon during photosynthesis, the carbon can end up in a number of places. It might end up in sugar, cellulose, lignin, starch, proteins, or lipids. One of the main components that biofuel proponents care about is a group of lipid compounds called triacylglycerides (TAGs). One role for TAGs in plants is energy storage. Biofuel manufacturers can convert TAGs into biodiesel via transesterification or into jet biofuel via hydrotreatment.

The TAGs produced naturally by camelina plants are fatty acids that contain unsaturated, 16-to-18-carbon chains. Genetic engineering might not only reduce the length of those chains but also take them from unsaturated to saturated (PLOS One 2017, DOI: 10.1371/journal.pone.0172296). Such TAGs wouldn’t have to go through as much energy-intensive hydrogenation and cracking to convert them into usable fuel, Sederoff explains.

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TAGs are typically stored in the fruits, nuts, and seeds of plants and are present in only small amounts in vegetative tissues such as leaves and stems. To increase oil production, some scientists are looking to engineer plants to bulk up the fatty acids synthesized in their leafy, green bits.

One study performed on tobacco plants, a model organism typically used in plant biotechnology research, demonstrated that tobacco’s leaves could reach a level of TAG accumulation similar to what’s found in soybean seeds.

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Another plant that scientists recently engineered to accumulate oil in its leaves and stems is sugarcane. Sugarcane is attractive to biofuel proponents because of its high biomass. Typically, sugarcane would be harvested by biofuel manufacturers for its sugars, and they would convert the saccharides into ethanol.

But researchers have calculated that increasing TAGs to 5% of sugarcane’s stem weight could, because of the plant’s high biomass, produce about four times as much oil per hectare of land as soybeans, plus more than 10,000 L of ethanol (GCB Bioenergy 2017, DOI: 10.1111/gcbb.12478). READ MORE

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