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

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.

Isolation and Characterization of Novel Chlorella Vulgaris Mutants With Low Chlorophyll and Improved Protein Contents for Food Applications

“…In addition, increased ash content in chlorophyllfree biomass has also been previously reported (Li et al, 2016), suggesting that the mineral metabolism might have also been affected in the mutants. Overall, WT cultures revealed proximate composition values within those previously reported for C. vulgaris grown in heterotrophic conditions (Kim et al, 2019;Canelli et al, 2020), while MT01 and MT02 displayed significantly higher protein contents. Therefore, the low ash associated with high protein contents of mutants, adds to these cultures improved nutritional profiles with commercial interest for their application as feedstocks for food products.…”

Enhancement of Lipid Production under Heterotrophic Conditions by Overexpression of an Endogenous bZIP Transcription Factor in Chlorella sp. HS2

“…In efforts to improve growth and lipid production of Chlorella sp. HS2, various cultivation methods have been reported [22,[37][38][39]43]. Particularly, Yun et al (2019) and reported optimized heterotrophic conditions for Chlorella sp.…”

Plant anti-aging: Delayed flower and leaf senescence in Erinus alpinus treated with cell-free Chlorella cultivation medium

“…ABC001 and HS2 were previously found to be highly efficient strains for the production of beneficial compounds such as specific lipids and antioxidant pigments. [21][22][23][24][25]31 Especially, Chlorella sp. HS2 accumulated high levels of the antioxidant pigments β-carotenoid and lutein.…”

“…ABC001 and HS2 were not previously applied to higher plants but demonstrated high efficiency growth characteristics suitable for biofuel production. [21][22][23][24][25] Rootdrenching of three Chlorella supernatant significantly delayed flower and leaf senescence of E. alpinus through different function immunity-eliciting chemical or fertilizer. This is the first report of the novel plant anti-aging strategy using cellfree supernatant of microalgae Chlorella.…”