Near-infrared spectroscopy for microalgae studies: A comprehensive review of applications and outlooks

Microalgae are photosynthetic organisms typically found in natural freshwater and marine environments. They are important in wastewater treatment for pollution removal and resource recovery. Due to species-specific differences in physiological structure and biochemical composition, microalgae exhibit complex internal metabolisms and dynamic interactions with external environmental factors. However, many of their traits such as components, elements, and genetic information, and key mechanisms including growth and development, metabolism, and toxicological responses, remain insufficiently understood. As an effective, efficient, accurate, and nondestructive optical method, near-infrared (NIR) spectroscopy has great potential for studying microalgal properties. Considering the lack of literature reviews in this field, this paper highlights NIR applications on microalgae from three major categories: components testing, growth monitoring, and contaminants supervision using microalgae as a mediating object. It also discusses the existing challenges and future directions from aspects of microalgae, NIR, predictive modeling, and sustainability. Overall, this review aims to provide a comprehensive overlook and promote further advances at the intersection of microalgae research and NIR spectroscopy.