Inoculum Optimization in Chlorella Cultivation: Enhancing Biomass Production for Marine Aquaculture and Environmental Remediation

Chlorella, a unicellular microalga, is widely recognized for its rapid growth and high nutritional value. This study investigated the effect of different inoculum concentrations on the growth performance of Chlorella spp. over nine days in batch culture. Cultures were grown in 250-mL Erlenmeyer flasks containing BG-11 medium under a 14-hour light (4800 lux)/10-hour dark photoperiod at 27 °C. The initial inoculation density was set to 2×10 6 cells/mL, and five inoculum concentrations (2.5%, 5%, 10%, 15%, and 20%) were prepared from cultures harvested at the early stationary phase and tested under controlled laboratory conditions. Optical density (OD₆₈₀) was measured daily to monitor growth. All cultures exhibited exponential growth during the first five days, reflecting favorable environmental conditions and active cellular metabolism. By day seven, the 15% and 20% inocula achieved the highest biomass, reaching a maximum OD₆₈₀ of approximately 1.5–1.6. The 15% inoculum was identified as optimal, balancing biomass yield and resource efficiency by achieving comparable productivity to the 20% inoculum while requiring less initial biomass input. These results provide important insights into optimizing Chlorella spp. cultivation, particularly regarding inoculum concentration as a key factor for maximizing biomass productivity. The observed growth dynamics and biomass yields highlight the suitability of Chlorella spp. for integration into marine aquaculture systems, where efficient nutrient recycling and high-value biomass production are essential. Moreover, the robust growth under controlled conditions supports its potential application in biotechnology-based environmental remediation, such as wastewater treatment and carbon sequestration, due to its capacity to absorb excess nutrients and pollutants from aquatic environments.