Efficient pH and dissolved CO2 conditions for indoor and outdoor cultures of green alga Parachlorella

Akari Takagi; Misato Nagao; Yuya Uejima; Daisaku Sasaki; Munehiko Asayama

doi:10.3389/fbioe.2023.1233944

Efficient pH and dissolved CO₂ conditions for indoor and outdoor cultures of green alga Parachlorella

Front Bioeng Biotechnol. 2023 Sep 11:11:1233944. doi: 10.3389/fbioe.2023.1233944. eCollection 2023.

Authors

Akari Takagi¹, Misato Nagao¹, Yuya Uejima¹, Daisaku Sasaki², Munehiko Asayama^{1

3}

Affiliations

¹ College of Agriculture, Ibaraki University, Ibaraki, Japan.
² BioX Chemical Industries Co., Ltd., Hiroshima, Japan.
³ United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.

Abstract

Efficient pH and dissolved CO₂ conditions for indoor (50-450 mL scale) and outdoor (100-500 L scale) culture of a green alga BX1.5 strain that can produce useful intracellular lipids and extracellular polysaccharides were investigated for the first time in Parachlorella sp. The cultures harvested under 26 different conditions were analysed for pH, dissolved CO₂ concentration, and the biomass of extracellular polysaccharides. The BX1.5 strain could thrive in a wide range of initial medium pH ranging from 3 to 11 and produced valuable lipids such as C16:0, C18:2, and C18:3 under indoor and outdoor culture conditions when supplied with 2.0% dissolved CO₂. Particularly, the acidic BG11 medium effectively increased the biomass of extracellular polysaccharides during short-term outdoor cultivation. The BG11 liquid medium also led to extracellular polysaccharide production, independent of acidity and alkalinity, proportional to the increase in total sugars derived from cells supplied with high CO₂ concentrations. These results suggest Parachlorella as a promising strain for indoor and outdoor cultivation to produce valuable materials.

Keywords: Parachlorella; algae; biorefinery; carbohydrate; lipid; polysaccharide.

Grants and funding

This research was partially supported by a project from Ibaraki University (to MA), the Japan Society for Bioscience, Biotechnology, and Agrochemistry (MA and DS: Academic-Industrial R&D Support for Small-to-Medium Enterprises, SME-3), the Japan Science and Technology Agency (to MA and DS: OPERA, JPMJOP1832), and the Japan Science and Technology Agency (MA and DS: A-STEP and JPMJTM19BT).