Evaluation of the potential of two native microalgae isolates of the Persian Gulf in different culture scales for possible bioethanol production

In the wake of extensive fossil fuel use and CO2 accumulation in the environment, biofuel production from microalgae may be more effective and leave a less environmental footprint. The nutritional and environmental factors and their interactions affect the growth performance and biochemical constitution of different microalgae. The behavior of microalgal cells in different culture scales depends on the mentioned factors. The present study evaluates the potential of two microalgae isolates, Picochlorum D8, and Chlorella S4, in different culture scales. High biomass and carbohydrate productivity were considered as important factors to identify the potent microalga. Acid-thermal pretreatment was applied to measure the carbohydrate concentration. The carbohydrate composition of selected microalga was investigated using thin-layer chromatography (TLC). According to the observations, Chlorella S4 exhibited the best dry biomass and carbohydrate productivity of 62 ± 6 mg/L/d and 19.16 ± 1.57 mg/L/d in a 200 L indoor open raceway pond, respectively. For Picochlorum D8, the highest biomass productivity of 26.24 ± 0.625 mg/L/d and carbohydrate productivity of 7.45 ± 0.53 mg/L/d were achieved in a 2 L Erlenmeyer flask. Based on TLC analysis, glucose, galactose, and xylose were detected as the main monosaccharides in Chlorella S4 hydrolysate. The current study demonstrated Chlorella S4’s capacity to produce biomass in a large-scale system. The relatively high carbohydrate content of this microalga makes it a promising raw material for potentially producing bioethanol.