Assessment of a Novel Oleaginous Filamentous Microalga Klebsormidium sp. Lgx80 (Streptophyta, Klebsormidiales) for Biomass and Lipid Production1.

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 (ø4.5 × 60 cm) photobioreactor under laboratory conditions. Growth and lipid production of the new strain were further evaluated in an outdoor pilot-scale tubular photobioreactor. 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 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 outdoors in a 13,000-L tubular photobioreactor 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.

Evaluation of several flocculants for flocculating microalgae.

Flocculation of microalgae with chitosan, polyacrylamide, Al2(SO4)3, NaOH and HNO3 was evaluated. Their flocculation efficiencies and optimal dosages were discussed. The effects of the flocculants on cells viability were also investigated and the cells were found to be intact during the flocculation process. Moreover, the effects of flocculants on the extractions were evaluated. Lipid content after flocculants treatments showed no significant differences. Carbohydrate content was lower but protein content was higher after NaOH treatment than those after other treatments. Furthermore, the five flocculated media maintained approximate growth yields to that of the fresh medium in microalgal cultivation, indicating the five flocculated media could be recycled, thereby reducing the cost of biodiesel production from microalgae. Finally, economic comparison of the flocculants was made and the cost of using HNO3, including flocculating cells and recycling medium, was found to be the lowest.

Profiling of carotenoids in six microalgae (Eustigmatophyceae) and assessment of their ß-carotene productions in bubble column photobioreactor.

The profiles of carotenoids and production of ß-carotene by six eustigmatophytes, Eustigmatos magnus, Eustigmatos polyphem, Eustigmatos vischeri, Vischeria helvetica, Vischeria punctata and Vischeria stellata, grown in a bubble column photobioreactor were measured. All eustigmatophytes contained ß-carotene, violaxanthin and vaucheriaxanthin as their major carotenoids and accumulated large amount of ß-carotene, which accounted for over 50 % of total carotenoids. Maximum intracellular ß-carotene contents ranged 1.5-3.5 % of dry wt and in V. stellata it reached 5.9 % dry wt, accompanied by a biomass dry wt >7.3 g/l, with the highest up to 9.8 g/l. These eustigmatophytes are thus promising producers of ß-carotene.