Lipid and chitin nanofiber production during cultivation of the marine diatom Cyclotella sp. to high cell density with multistage addition of silicon and nitrate
2017
Ozkan, Altan | Rorrer, Gregory L.
The centric marine diatom Cyclotella sp. requires silicon in the form of Si(OH)₄ for cell wall biosynthesis, makes lipids for biofuels, and extrudes novel chitin nanofibers as a valued co-product for biomedical and nutraceutical applications. Due to the low solubility of Si(OH)₄ in seawater (<2 mM), to achieve high cell number density, dissolved Si was added in steps, with Si consumption between each step. A multistage nutrient delivery process with 19 mM cumulative Si delivery achieved a cell number density of 4 · 10⁷ cells mL⁻¹ (5.0 g ash-free dry weight (AFDW) L⁻¹), ten times higher than that of the two-stage Si addition process. Cell number and chitin production profiles were linear with time, commensurate with the Si consumption profile. The productivities of biomass and chitin were 0.29 g AFDW L⁻¹ day⁻¹ and 45 mg chitin L⁻¹ day⁻¹, with chitin yield of 19 wt% in the biomass. Lipid production could not be sustained due to light attenuation, and yield decreased from 39 wt% (two-stage process) to 8 wt% (multistage process).
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