Abstract
In this study, we characterized the potential of colony-forming green algae, Botryosphaerella sudetica KNUA107, isolated from Ulleung Island, South Korea, as a bioresource and analyzed the effects of mixotrophic cultivation on its bioresource production efficiency. Internal transcribed spacer (ITS) (ITS1, 5.8S, and ITS2), ribulose bisphosphate carboxylase large subunit (rbcL), and elongation factor Tu (tufa) regions were used for molecular identification and phylogenetic analysis. B. sudetica KNUA107 had a strong relationship with the green algae of Botryococcus and Botryosphaerella genera, which are colony-forming species, and was also associated with members of the Neochloris genus. To improve biomass productivity, we tested mixotrophic cultivation conditions using several organic carbon sources. Glucose supplementation stimulated B. sudetica KNUA107 growth and reduced the time needed to reach the stationary phase. In addition, the colony size was 1.5–2.0 times larger with glucose than in photoautotrophic cultures, and settleability improved in proportion to colony size. The total lipid content and biomass productivity were also higher in cultures supplemented with glucose. Among the lipid components, saturated fatty acids and monounsaturated fatty acids had the highest proportion. Our study suggests that B. sudetica KNUA107, which has enhanced efficiency in biomass production and lipid components under mixotrophic cultivation, has high potential as a bioresource.
Highlights
Green algae are photosynthetic organisms used as bioresources (Vanthoor-Koopmans et al, 2013; Muhammad et al, 2020)
The sequence analyses suggested that B. sudetica KNUA107 was a species similar to Botryococcus sp., Botryosphaerella sudetica, and Neochloris aquatica (Supplementary Table 2)
Previous data indicated that some members of these three green algae genera have colony-forming abilities and morphological characteristics similar to those of B. sudetica KNUA107 (Komárek, 1989; Senousy et al, 2004; Pribyl and Cepák, 2007; Tanoi et al, 2011)
Summary
Green algae are photosynthetic organisms used as bioresources (Vanthoor-Koopmans et al, 2013; Muhammad et al, 2020) They are promising bioenergy feedstocks and can produce more biomass per unit area than terrestrial plants (Cooney et al, 2009; Vanthoor-Koopmans et al, 2013; Bhushan et al, 2020), wherever water, light, and inorganic materials (nitrogen, phosphorous, and trace elements) are available (Smith and Wiedeman, 1964; Cooney et al, 2009; Lu et al, 2020). Several processes are needed to harvest biomass from culture (centrifugation or filtering) and extract lipids from the harvested biomass (Shelef et al, 1984; Cooney et al, 2009; Li et al, 2020). To efficiently produce bioenergy with green algae, it is necessary to reduce the associated costs by improving the process efficiency (Delrue et al, 2012)
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