Silicon in cereal straw: role of transport proteins, interactions with nitrogen supply and implications for bioenergy potential

Research output: Book/ReportPh.D. thesisResearch

  • Emiko Murozuka
Silicon (Si) is known to be a beneficial element for plants. However, when plant residues are to be used as feedstock for second generation bioenergy, Si may reduce the suitability of the biomass for biochemical or thermal conversion technologies.
The objective of this PhD study was to investigate how Si influences cell wall composition in cereal straw and, consequently, the enzymatic saccharification efficiency. Considering the importance of Nitrogen (N) fertilization in cereal production, an additional objective was to elucidate the effect of N supply on Si concentration and cell wall composition.
The Si concentration in wheat straw differed significantly among genotypes and growth locations. Wheat straw with high Si concentration released less xylose during enzymatic saccharification suggesting inhibition by Si deposited in hemicelluloses. N supply had a distinct effect on Si concentration in both wheat and rice straw. In field grown wheat, the Si concentration decreased by more than 50 % in response to N application, while at the same time the concentration of lignin increased. Assuming that there was no limitation in Si availability under field conditions, the drastic reduction in straw Si concentration was likely to be associated with decreased Si uptake. A significant reduction in xylose release was observed during enzymatic saccharification of the straw grown with high N supply, probably reflecting their higher lignin concentration.
To further study Si uptake and transport, a mutant in Si influx transporter BdLsi1 was identified. BdLsi1 belongs to the major intrinsic protein family. The mutant BdLsi1 protein had an amino acid change from proline to serine in the highly conserved NPA motif. The mutation caused a defect in channeling of Si as well as other substrates such as germanium and arsenite. The Si concentration in the mutant plant was significantly reduced by more than 80 %. Rice mutants defective in Si transporters OsLsi1 and OsLsi2 also showed significantly lower straw Si concentration.
It is concluded that the quality of straw biomass for bioenergy purposes can be optimized by proper selection of genotype. Optimization of the level of N supply is also important considering the fact that both organic and inorganic cell wall components with impact on saccharification efficiency are affected
Original languageEnglish
PublisherDepartment of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
Number of pages185
Publication statusPublished - 2013

ID: 91897496