Assessment of biomass potentials of microalgal communities in open pond raceways using mass cultivation

Seung-Woo Jo; Jeong-Mi Do; Ho Na; Ji Won Hong; Il-Sup Kim; Ho-Sung Yoon

doi:10.7717/peerj.9418

Assessment of biomass potentials of microalgal communities in open pond raceways using mass cultivation

PeerJ. 2020 Jul 16:8:e9418. doi: 10.7717/peerj.9418. eCollection 2020.

Authors

Seung-Woo Jo¹, Jeong-Mi Do^{2

3}, Ho Na^{2

3}, Ji Won Hong⁴, Il-Sup Kim⁵, Ho-Sung Yoon^{1

2

3

5}

Affiliations

¹ Department of Energy Science, Kyungpook National University, Daegu, South Korea.
² Department of Biology, Kyungpook National University, Daegu, South Korea.
³ School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daegu, South Korea.
⁴ Department of Hydrogen and Renewable Energy, Kyungpook National University, Daegu, South Korea.
⁵ Advanced Bio-resource Research Center, Kyungpook National University, Daegu, South Korea.

Abstract

Metagenome studies have provided us with insights into the complex interactions of microorganisms with their environments and hosts. Few studies have focused on microalgae-associated metagenomes, and no study has addressed aquatic microalgae and their bacterial communities in open pond raceways (OPRs). This study explored the possibility of using microalgal biomasses from OPRs for biodiesel and biofertilizer production. The fatty acid profiles of the biomasses and the physical and chemical properties of derived fuels were evaluated. In addition, the phenotype-based environmental adaptation ability of soybean plants was assessed. The growth rate, biomass, and lipid productivity of microalgae were also examined during mass cultivation from April to November 2017. Metagenomics analysis using MiSeq identified ∼127 eukaryotic phylotypes following mass cultivation with (OPR 1) or without (OPR 3) a semitransparent film. Of these, ∼80 phylotypes were found in both OPRs, while 23 and 24 phylotypes were identified in OPRs 1 and 3, respectively. The phylotypes belonged to various genera, such as Desmodesmus, Pseudopediastrum, Tetradesmus, and Chlorella, of which, the dominant microalgal species was Desmodesmus sp. On average, OPRs 1 and 3 produced ∼8.6 and 9.9 g m^-2 d^-1 (0.307 and 0.309 DW L^-1) of total biomass, respectively, of which 14.0 and 13.3 wt% respectively, was lipid content. Fatty acid profiling revealed that total saturated fatty acids (mainly C16:0) of biodiesel obtained from the microalgal biomasses in OPRs 1 and 3 were 34.93% and 32.85%, respectively; total monounsaturated fatty acids (C16:1 and C18:1) were 32.40% and 31.64%, respectively; and polyunsaturated fatty acids (including C18:3) were 32.68% and 35.50%, respectively. Fuel properties determined by empirical equations were within the limits of biodiesel standards ASTM D6751 and EN 14214. Culture solutions with or without microalgal biomasses enhanced the environmental adaptation ability of soybean plants, increasing their seed production. Therefore, microalgal biomass produced through mass cultivation is excellent feedstock for producing high-quality biodiesel and biofertilizer.

Keywords: Biodiesel; Biofertilizer; Mass cultivation; MiSeq; Microalgal community.

Grants and funding

This study was supported by a grant from the National Research Foundation of Korea (NRF-2017R1A2B4002016). This work was supported by a grant from the Next-Generation BioGreen 21 Program (No. PJ013240), Rural Development Administration, Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.