Assessment of the lipid production potential of six benthic diatom species grown in airlift photobioreactors

In recent years diatoms have emerged as a major algal source for the production of bioactive compounds. Marine diatoms grow quickly and can store high amount of lipids. Unfortunately, they are little studied and underexploited resources. The current work deals with an original and rarely investigated source of diatoms: intertidal mudflats. It aims to evaluate the lipid production potential of some strains of benthic diatom species, isolated and hosted in the Nantes Culture Collection (NCC) when cultivated in an airlift photobioreactor. Six strains known for their high biomass and/or lipid productivity: Amphora sp. (NCC169), Entomoneis paludosa (NCC18.2), Nitzschia alexandrina (NCC33), Nitzschia sp. (NCC109), Opephora sp. (NCC366), and Staurosira sp. (NCC182) were cultivated in airlift photobioreactors for the first time. Their lipid class composition, fatty acid, and sterol distribution were studied. Total lipid production varied from 11.4 ( Amphora sp.) to 41%DW ( Staurosira sp.). Neutral lipid amounts varied from 23 ( Amphora sp.) to 76% ( Staurosira sp.) of total lipids (%TL). Glycolipids ranged from 18 ( Staurosira sp.) to 59%TL ( Opephora sp.) and phospholipids accounted for 6 ( Staurosira sp.) to 26%TL ( Amphora sp.). Some qualitative and quantitative differences were identified in both fatty acid and sterol composition in the different strains analyzed. Staurosira sp. seems to be the most promising species in terms of lipid production and most particularly in triacylglycerol production. Entomoneis paludosa produced phytosterols and eicosapentaenoic acid (EPA), compounds with potential for application in the pharmaceutical sector. Nitzschia alexandrina produced squalene and low levels of saturated fatty acids which could both be interesting in the nutraceutical industry as antioxidants.