Assessment of a novel oleaginous filamentous microalga Klebsormidium sp. Lgx80 (Streptophyta, Klebsormidiales) for biomass and lipid production

Commercial cultivation of eukaryotic microalgae has so far employed a unicellular form of species only (e.g., Chlorella pyrenoidosa, Dunaliella salina and Haematococcus pluvialis). In this study, we assessed the feasibility of using the filamentous eukaryotic microalga Klebsormidium sp. LGX80 as a new cultivar for biomass and lipid production. The effects of different forms and concentrations of nitrogen on growth and lipid production of Klebsormidium sp. LGX80 were studied by using a glass column (o4.5×60 cm) photobioreactor under laboratory conditions. Growth and lipid production of the new strain were further evaluated in a pilot-scale tubular photobioreactor outdoors. The results showed that when supplied with urea as a source of nitrogen Klebsormidium sp. LGX80 yielded a final biomass concentration of 8.49±0.10 g · L-1 in which a cellular lipid content of was 59.2±0.4% DW. Under such conditions, the biomass and lipid productivities were 471.7±5.9 and 248.1±0.0 mg · L-1 · d-1 , respectively. Fatty acid analysis revealed that the main fatty acids of Klebsormidium sp. LGX80 were palmitic acid (C16:0), linoleic acid (C18:2ω6) and linolenic acid (C18:3ω3), of which linoleic acid (C18:2ω6) accounted for up to 67.5±0.1% of total fatty acids. When grown in a 13,000 liter tubular photobioreactor outdoors with an initial nitrogen concentration of 3 mM urea, Klebsormidium sp. LGX80 reached the highest biomass concentration of 2.63±0.09 g · L-1 with the cells containing 38.0±0.5% lipids (% DW), resulting in the volumetric biomass and lipid productivities of 147.2±3.6 and 37.9±0.9 mg · L-1 d-1 respectively. The results of light:dark cycle experiment showed that a durative and prolonged light irradiation hindered the biosynthesis of chlorophyll a and chlorophyll b in the cells, but promoted the carotenoid accumulation. These results suggested that Klebsormidium sp. LGX80 can be a potential oleaginous filamentous microalga for commercial production of microalgal oils.