title: Biosynthesis of silicon-germanium oxide nanocomposites by the marine diatom Nitzschia frustulum.
abstract: The biomineralization capacity of the photosynthetic marine diatom Nitzschia frustulum was harnessed to fabricate Si-Ge oxide nanocomposite materials. Germanium was incorporated into the diatom cell by a two-stage cultivation process. In stage 1, the N. frustulum cell suspension was grown up to cell density of 3 x 10(6) cells/mL in 0.35 mM silicic acid within a bubble-column photobioreactor. In stage 2, when all of the soluble silicon was consumed, 0.10 mM Ge(OH)4 or a mixture of 0.020 mM Ge(OH)4 and 0.25 mM Si(OH)4 were added to Si-starved cells. The cells assimilated soluble germanium by a surge uptake mechanism. The cell mass was thermally annealed in air at 800 degrees C for 6 h to oxidize carbonaceous materials. The thermally annealed cell biomass was characterized by TEM-EDS, FT-IR, and XRD. These measurements confirmed the formation nanostructured Ge-Si oxides composed of CaSiO3 and Ca3GeO5.
authors.affiliation: Department of Chemical Engineering, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Rorrer
authors.forename: Chih-Hung
authors.initials: CH
authors.lastname: Chang
authors.forename: Shu-Hong
authors.initials: SH
authors.lastname: Liu
authors.forename: Clayton
authors.initials: C
authors.lastname: Jeffryes
authors.forename: Jun
authors.initials: J
authors.lastname: Jiao
authors.forename: James A
authors.initials: JA
authors.lastname: Hedberg
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry / Q000378:metabolism*; D018929:Cell Culture Techniques / Q000379:methods*; D003460:Crystallization / Q000379:methods; D017377:Diatoms / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D005857:Germanium / Q000737:chemistry / Q000378:metabolism*; D008386:Marine Biology / Q000379:methods; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D017640:Silicates / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017610:Calcium Compounds; D017640:Silicates; D005857:Germanium; C040516:germanium oxide; C031293:calcium silicate