Enhancing Chlorella vulgaris Productivity Through Coordinated CO₂ and pH Regulation with Consideration of Post-harvest Storage Stability

Abstract

Microalgae such as Chlorella vulgaris are increasingly recognized as sustainable biological resources that support several UN Sustainable Development Goals (SDGs), particularly those related to affordable clean energy, sustainable production, and climate action. Despite their promise, large-scale cultivation remains constrained by environmental factors and nutrient availability. This study aimed to enhance the biomass productivity of Chlorella vulgaris by coordinating CO₂ enrichment and pH regulation under pilot-scale cultivation conditions. The result showed that alkaline pH gave an initial boost to growth during the first 10 days. Still, as pH shifted towards neutrality, biomass growth accelerated, reaching its highest chlorophyll concentration of 1,853.5 µg L⁻¹. Moreover, CO₂ injection at 2 mL min⁻¹ further enhanced growth, with chlorophyll concentration increasing to 2,211 µg L⁻¹. Under optimal integrated conditions, total chlorophyll increased from 827.48 to 2,055.7 µg L⁻¹, and metabolic activity improved from 57.43% to 82.65% within two weeks. Also, storage at 8 °C preserved chlorophyll content, showing the importance of post-harvest management. These results highlight that integrated CO2 and pH management could significantly shorten cultivation time and improve process efficiency in Chlorella vulgaris cultivation. As a result, it can support more efficient and sustainable strategies for microalgae-based bioprocesses.