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. 2019 Dec 18;9(1):19383.
doi: 10.1038/s41598-019-55854-9.

Optimization of heterotrophic cultivation of Chlorella sp. HS2 using screening, statistical assessment, and validation

Hee Su Kim  1 , Won-Kun Park  2 , Bongsoo Lee  3 , Gyeongho Seon  1 , William I Suh  4 , Myounghoon Moon  5 , Yong Keun Chang  6   7
Affiliations

Optimization of heterotrophic cultivation of Chlorella sp. HS2 using screening, statistical assessment, and validation

Hee Su Kim et al. Sci Rep. .

Abstract

The heterotrophic cultivation of microalgae has a number of notable advantages, which include allowing high culture density levels as well as enabling the production of biomass in consistent and predictable quantities. In this study, the full potential of Chlorella sp. HS2 is explored through optimization of the parameters for its heterotrophic cultivation. First, carbon and nitrogen sources were screened in PhotobioBox. Initial screening using the Plackett-Burman design (PBD) was then adopted and the concentrations of the major nutrients (glucose, sodium nitrate, and dipotassium phosphate) were optimized via response surface methodology (RSM) with a central composite design (CCD). Upon validation of the model via flask-scale cultivation, the optimized BG11 medium was found to result in a three-fold improvement in biomass amounts, from 5.85 to 18.13 g/L, in comparison to a non-optimized BG11 medium containing 72 g/L glucose. Scaling up the cultivation to a 5-L fermenter resulted in a greatly improved biomass concentration of 35.3 g/L owing to more efficient oxygenation of the culture. In addition, phosphorus feeding fermentation was employed in an effort to address early depletion of phosphate, and a maximum biomass concentration of 42.95 g/L was achieved, with biomass productivity of 5.37 g/L/D.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Effects of various concentrations of (a) carbon (glucose, sucrose, sodium acetate, and lactic acid) and (b) nitrogen sources (sodium nitrate, urea, ammonium chloride, and yeast extract) on the cell growth (calculated dry cell weight, DCW) under heterotrophic cultivation of Chlorella sp. HS2. Asterisks (*P <0.05, **P <0.01, ***P <0.001) refers to significant differences when compared with each glucose or nitrate concentrations.
Figure 2
Figure 2
Three-dimensional response surface and contour plots for dry cell weight (g/L) showing the effects of (a) glucose and sodium nitrate, (b) glucose and dipotassium phosphate, and (c) sodium nitrate and dipotassium phosphate concentrations.
Figure 3
Figure 3
Dry cell weight (DCW), total lipid productivity, and nutrient concentrations throughout the cultivation period under optimum conditions in 5-L fermenter: (a) DCW and glucose concentration; (b) nitrate and phosphate concentrations; (c) total lipid productivity and contents.
Figure 4
Figure 4
Dry cell weight (DCW), total lipid productivity, and nutrient concentrations throughout the cultivation period under P-feeding process conditions in 5-L fermenter: (a) DCW and glucose concentration; (b) nitrate and phosphate concentrations; (c) total lipid productivity and contents.
See this image and copyright information in PMC

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