Effective cultivation of microalgae for biofuel production: a pilot-scale evaluation of a novel oleaginous microalga Graesiella sp. WBG-1

Abstract

BackgroundCommercial production of microalgal biodiesel is not yet economically viable, largely because of low storage lipid yield in microalgae mass cultivation. Selection of lipid-rich microalgae, thus, becomes one of the key research topics for microalgal biodiesel production. However, the laboratory screening protocols alone cannot predict the ability of the strains to dominate and perform in outdoor ponds. Comprehensive assessment of microalgae species should be performed not only under the laboratory conditions, but also in the fields.ResultsLaboratory investigations using a bubbled column photobioreactor indicated the microalga Graesiella sp. WBG-1 to be the most productive species among the 63 Chlorophyta strains. In a 10 L reactor, mimicking the industrial circular pond, Graesiella sp. WBG-1 produced 12.03 g biomass m−2 day−1 and 5.44 g lipids (45.23 % DW) m−2 day−1 under 15 mol m−2 day−1 artificial light irradiations. The lipid content decreased to ~34 % DW when the microalga was cultured in 30 L tank PBR under natural solar irradiations, but the decline of lipid content with scaling up was the minimum among the tested strains. Based on these results, the microalga was further tested for its lipid production and culture competitiveness using a pilot-scale raceway pond (200 m2 illuminated area, culture volume 40,000 L). Consequently, Graesiella sp. WBG-1 maintained a high lipid content (33.4 % DW), of which ~90 % was storage TAGs. Results from the outdoor experiments indicated the nice adaptability of the Graesiella sp. WBG-1 to strong and fluctuating natural solar irradiance and temperature, and also demonstrated several other features, such as large cell size (easy for harvest and resistant to swallow by protozoa) and tolerance to high culture pH (helpful to CO2 fixation).ConclusionsGraesiella sp. WBG-1 was a promising strain capable of accumulating large amount of storage lipid under nature solar irradiance and temperature. The high lipid content of 33.4 % DW was achieved for the first time in pilot-scale raceway pond. The results also provide evidence for the feasibility of using low-cost raceway pond for autotrophic cultivation of microalgae for biodiesel production.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0541-y) contains supplementary material, which is available to authorized users.

Impact of Flue Gas Compounds on Microalgae and Mechanisms for Carbon Assimilation and Utilization

“…cultivated Graesiella sp. WBG‐1 in a 40 000 L raceway pond with an illumination area of 200 m 2 for lipid production . The utilization rate of CO 2 under a high pH (9.0±0.5) environment in this system was reported to be 65.7 %.…”

An open outdoor algal growth system of improved productivity for biofuel production

“…Seven samples were collected from the light distributed Growth System 1 – four from the bottom horizontal region at different locations and three from different vertical panels. Volume of individual samples utilized for the dry mass measurements was 20–40 mL (depending on the culture density) . The algal samples were filtered through a Millipore glass fibre filter (0.2 µm pore size; 47 mm diameter) held in a Sterifil filter assembly (connected to vacuum).…”

“…Volume of individual samples utilized for the dry mass measurements was 20-40 mL (depending on the culture density). 22 The algal samples were filtered through a Millipore glass fibre filter (0.2 μm pore size; 47 mm diameter) wileyonlinelibrary.com/jctb held in a Sterifil filter assembly (connected to vacuum). They were washed twice with deionized water and dried at 100 ∘ C in a hot air oven (for an hour) to constant weight.…”

Emerging Technologies in Algal Biotechnology: Toward the Establishment of a Sustainable, Algae-Based Bioeconomy

“…Besides stagnant ponds, the cheapest option for large-scale microalgal production is a shallow open pond raceway design that includes basic mixing. Compared to other photo-bioreactor (PBR) designs, they also have lower energy requirements, lower capital and operating costs, and can be built at a large scale (Brennan and Owende, 2010;Borowitzka and Vonshak, 2017). However, they generally have the lowest areal productivity (<10 g m −2 d −1 compared to >20 g m −2 d −1 in some PBRs) (De Vree et al, 2015).…”