Magnetically modified nanogold-biosilica composite as an effective catalyst for CO oxidation

•The temperature-dependent biosynthesis of gold nanoparticles and its subsequently anchoring on diatom cells in one step.•Simple magnetic modification of prepared bionanocomposite by ferrofluid.•First testing of magnetically modified and unmodified nanogold-biosilica composites in CO catalytic oxidation.•100% of CO conversion at 330 °C over magnetically modified nanogold-biosilica sample.