New research has shown that genetically modified trees with less lignin could reduce the energy and climate impacts of paper products.
Paper products are desirable – they are recyclable, biodegradable and renewable.
The main ingredient of paper is cellulose fibre. However, the separation of these fibres from other substances found in the plant – for example stiff, woody material lignin, which forms key structural materials in the support tissues of most plants – has a heavy environmental cost. In the process, paper mills generate millions of tonnes of chemical waste and greenhouse gas emissions.
Researchers have shared details of a new approach that could help reduce this environmental burden. The answer can be found in a process known as CRISPR- or ‘clustered regularly interspaced short palindromic repeats’, which can be used by scientists to selectively modify the DNA of living organisms.
Using this gene-editing technology, the team grew engineered poplar trees containing much less lignin than usually found. They claim milling such trees will help lower the pollution associated with papermaking and save the sector billions of dollars.
Poplars – a fast-growing tree common in plantations – are a popular input source for paper production. Water and chemicals are used to penetrate the tough lignin structures and separate out a wet pulp of cellulose fibres. These are then pressed and dried to produce paper.
Jack Wang and Rodolphe Barrangou, both biotechnologists at North Carolina State University (NC), alongside a team of colleagues, built a computer model based on decades worth of forest biotechnology studies. This data was used to predict how simultaneously changing poplar genes related to lignin production might affect the wood composition and growth rate of the trees, among other things.
After evaluating nearly 70,000 different gene-editing combinations, the team discovered that 99.5 per cent of the changes would be detrimental, leading to effects such as drooping limbs and stems. However, 347 combinations seemed to boost cellulose, reduce lignin, or both.
The NC team used CRIPSR to create the gene changes associated with 174 of the most promising combinations. They grew these engineered trees in a greenhouse.
Six months later, the lignin content of the most promising varieties had reduced by 49.1% and their cellulose-to-lignin content increased by 228 per cent.
According to the researchers, if an average paper mill used these varieties it could increase its paper output by 40 per cent, cut its greenhouse emissions by 20 per cent, and boost its lifetime profits by about $1 billion.
Barrangou said these stats should create an impetus for industry to adopt the new technology.
However, adopting and embracing this new approach is likely to take some time.
The team now needs to conduct field trials to ensure the novel trees can grow to maturity under real-world conditions. Lignin not only helps trees stand up to windstorms, but also protects them from insects.
And as the research team explained, some of the trees with edited DNA did not grow to have the same volume as regular poplars.
Wang and Barrangou aim to commence field trials of CRISPR-edited poplars. They are also working to introduce similar gene edits into eucalyptus and pine trees, which are also widely used to make paper.
Source – Science.org
