Scientists manipulate plant genes for biofuel
Europeans are concerned about finding ways to sustain energy for the future. With this in mind, researchers are examining ways to generate biofuels from plant biomass at a low cost. The problem, however, is that some plants contain lignin and hemicelluloses, which are not easily converted into biofuels. Researchers from Denmark, Thailand and the United States may have found a solution to this problem. They used gene manipulation techniques to engineer plants that can be broken down into biofuels. The study was recently presented in the journal Biotechnology for Biofuels.
Experts have identified how plants high in lignin and hemicelluloses - lignocellulosic biomass - contain high levels of pentose sugars that cannot easily ferment into fuels compared to plants with hexose sugars. Led by the Lawrence Berkeley National Laboratory in the United States, the researchers in this study decided to engineer plants with smaller quantities of xylan - the major non-cellulosic polysaccharide - present in secondary cell walls so as to contribute to biofuel production.
The team used three mutant strains of Arabidopsis deficient in xylan - irregular xylem (irx) mutants irx7, irx8 and irx9 - to engineer plants that contain low xylan and to improve properties that make the breakdown of carbohydrate into simple sugars (saccharification) more simple.
According to the researchers, the irx mutants usually show severe dwarf phenotypes triggered by xylem vessel collapse and consequent impaired transport of water and nutrients. They believed restoring the plants' xylan biosynthesis would complement the mutations.
They manipulated the promoter regions of vessel-specific VND6 and VND7 transcription factor genes in order to reintroduce xylan biosynthesis into the xylem of irx7, 8 and 9. The team observed that the ensuing phenotypes totally restored wild-type growth patterns in some cases, making plants stronger because the mechanical properties were restored. They also succeeded in maintaining a low overall xylan content and in boosting saccharification properties. The outcome? Improved breakdown into biofuels.
The xylose levels in some plants dropped by up to 23%, while lignin levels in others fell by 18%. The researchers succeeded in restoring normal xylem function in the plants. They identified a 42% jump in the plants' saccharification yield after pretreatment.
'These results show that it is possible to obtain plants that have reduced amounts of xylan in their walls while still preserving the structural integrity of the xylem vessels,' said co-author Henrik V. Scheller from the Physical Biosciences Division, Lawrence Berkeley National Laboratory, as well as from the Joint Bioenergy Institute and the University of California, Berkeley. 'The xylan engineering system we present here is a great step towards tailored bioenergy crops that can be easily converted into biofuels. This approach in Arabidopsis has the potential to be transferred to other biofuel crop species in the near future, in particular, the poplar species.'
The researchers believe their findings could help lead to the development of an alternative energy that could significantly decrease the use of fossil fuels.
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Data Source Provider: Biotechnology for Biofuels; Lawrence Berkeley National Laboratory
Document Reference: Petersen, P.D., et al. 'Engineering of plants with improved properties as biofuels feedstocks by vessel-specific complementation of xylan biosynthesis mutants', Biotechnology for Biofuels, 2012.
Subject Index: Biotechnology; Coordination, Cooperation; Life Sciences; Scientific Research