To ease the industrial processing of plant biomass into energy, plants are engineered to contain less lignin. Unfortunately, this intervention typically leads to reduced yield. Researchers have now discovered a way to overcome this problem.
Moreover, the strategy the researchers at the VIB-Ghent University Center for Plant Systems Biology does not just restore the biomass yield. It increases the yield beyond that of wildtype plants. The findings of their study are an important step in the development of feedstock for biofuels and other bio-based materials. The results are published in the leading scientific journal Plant Physiology.
The increasing energy demand, depletion of fossil feedstock and global warming make a shift from today’s fossil-based economy towards a bio-based economy inevitable. Plant biomass serves as a renewable and carbon-neutral raw material for the production of bio-energy and a plethora of chemicals. However, the industrial processing of biomass is hindered by the presence of lignin, a building block of lignocellulose.
Lignocellulosic biomass is very rich in sugar, which can be used to produce e.g. bio-ethanol. But getting that sugar out of the plant is easier said than done. Indeed, although lignin strengthens the plant cell walls, it also essentially traps the sugars in there.
Prof. Wout Boerjan (VIB-UGent): "To tackle this problem, plants are engineered to contain less lignin. These plants show large improvements in processing efficiency for downstream applications - meaning we can get the sugar out of them more easily. But at the same time, a new problem arises: they have a yield penalty."
In their most recent study, prof. Wout Boerjan, PhD student Barbara De Meester and dr. Ruben Vanholme, looked for a solution to this problem. The starting point for their experiments was a dwarfed, mutant Arabidopsis plant containing only half the normal amount of lignin.
Barbara De Meester (VIB-UGent): "The water-conducting cells of the mutant plants collapse due to the lack of lignin, which negatively affects the transport of water through the stem. To restore normal growth, we allowed the biosynthesis of lignin to take place specifically in these water-conducting cells. Surprisingly, we didn’t just restore growth, but also increased the biomass of the plants by up to 60%."
Dr. Ruben Vanholme (VIB-UGent): "The combination of a low lignin amount and increased biomass in our engineered plants led to a four-fold increase in sugar release compared to wild plants. And it’s exactly that sugar we need to move from a fossil-based to a bio-based economy".
To take their findings to the next level, the scientists are currently investigating whether this strategy also works in poplar. Because of its fast growth, poplar is a promising feedstock for future biorefineries.
Vessel-Specific Reintroduction of CINNAMOYL-COA REDUCTASE1 (CCR1) in Dwarfed ccr1 Mutants Restores Vessel and Xylary Fiber Integrity and Increases Biomass, De Meester et al., Plant Physiology, 2018