recently published paper on diatoms, based on work by M. Thomas Kiran, Chief Technology Office of Kadambari Consultants Pvt Ltd, considers the potential for Cylindrotheca as a potential source for eicosapentaenoic acid, or EPA Omega-3 fatty acid.
Cylindrotheca, an epipelic benthic pennate diatom, was shown to hold promise as a nutraceutical source, and may be useful for aquaculture. Experiments were done on two Cylindrotheca species: Cylindrotheca fusiformis (UTEX 2084) and C. closterium, which was isolated from seawater collected offshore from Visakhapatnam, India. C. closterium was identified through microscopy and rDNA typing.
Type and concentration of nutrient components in the culture medium that promoted best growth and highest lipid accumulation were identified. Lipid content was gravimetrically estimated. For relative comparison of the effects of different culture media on lipid content, the researchers made estimations through rapid in situ screening method using Nile red staining and spectrofluorimetry.
The fatty acid profile of lipid was obtained through gas chromatography-mass spectroscopy. Nualgi, a commercially available micronutrient ready-mix with elements adsorbed as nanoparticles on a modified silica sol, was found to significantly boost growth in both Cylindrotheca species when used in lieu of a conventional micronutrient mix prepared from eight compounds.
Among the three nitrogen sources tested – sodium nitrate (NaNO3), urea, and ammonium chloride (NH4Cl) – best growth of C. fusiformis occurred on nitrate and urea, while NH4Cl was best for C. closterium. Lipid productivity was much higher in cultures supplied with NH4Cl for both Cylindrotheca species and compensated for lower biomass in C. fusiformis.
Both Cylindrotheca species were lipid rich; lipid constituted 18–27% of dry biomass in the medium with NaNO3. Among total fatty acids, polyunsaturated fatty acids constituted <40%, eicosapentaenoic acid 25%, and arachidonic acid ∼8% and ∼4% in C. fusiformis and C. closterium, respectively. NH4Cl, phosphate, and Nualgi micronutrient ready-mix in concentrations optimal for each strain contribute to a good culture medium for Cylindrotheca.
The research was performed by Keerthi Suman, Thomas Kiran, Uma Koduru Devi, and Nittala S. Sarma, collectively representing the Department of Botany and the Department of Marine Chemistry, School of Chemistry, Andhra University, Visakhapatnam 530003, Andhra Pradesh, India. Their work was published in Botanica Marina journal.