Potentials, Challenges of Biotech Poplars for Biofuels

The results of field trials with genetically modified (GM) poplar trees in Belgium and France have shown improved conversion of wood biomass into sugars for making bio-ethanol. The GM poplars produce low levels of cinnamoyl-CoA reductase (CCR) enzyme to suppress the formation of lignin polymer which is a tough barrier in biomass processing.

The study, published as an open access paper in Proceedings of the National Academy of Sciences (PNAS), also found that strong down-regulation of CCR affected biomass yield. The research team from Belgium, France and the United States concluded that the strategy of down-regulating the CCR may work to improve biomass processing if such yield penalty can be overcome.

The study showed that the suppression of the lignin biosynthesis in some trees is stronger than others, indicated by varying intensity of red coloration of the wood beneath the bark. The branches with the highest red coloration produce 160 percent more ethanol. On the average, the ethanol yield per gram of modified wood is 20 percent higher than that of non-modified wood.

The negative effect of CCR down-regulation points to the fact that the modified poplar trees appear to grow less rapid than non-modified trees. As the scientists begin to understand what causes the growth retardation, they plan to start to work on poplars that grow normally, but still have a stable suppression of the lignin production. In a new field trial in Belgium in 2014, trees that have been developed to suppress another enzyme through modern technique, for a more uniform lignin supression will be tested.