Starch Wastewater-integrated Microalgae Cultivation: A Circular Bioeconomy Approach for Bioremediation and Natural Carotenoids Production

The rapid expansion of starch processing industries has led to the discharge of large volumes of high-strength starch wastewater (SW). Conventional physicochemical wastewater treatments are limited by high energy consumption, substantial operational costs, and secondary sludge generation, thereby necessitating the development of sustainable alternatives. Interestingly, microalgae exhibit nutrient removal efficiencies of up to 99% chemical oxygen demand, 76.48% total nitrogen, and 89.9% total phosphorus, highlighting the potential for SW bioremediation while concurrently producing valuable biomass. Additionally, microalgae demonstrate significant potential for the biosynthesis of commercially valuable carotenoids. However, the large-scale commercialization of microalgal carotenoids is constrained by cost-associated barriers, particularly the requirement for freshwater and exogenous nutrient inputs in microalgae cultivation. Thus, integrating nontoxic nutrient-rich SW into the cultivation of microalgae would be a resource-efficient and sustainable alternative culture medium. Hence, this review discusses SW-integrated microalgae cultivation for bioremediation and carotenoids production, primarily focusing on resource recovery from corn, cassava, and potato SW. Moreover, SW pretreatment and optimization strategies for microalgae cultivation, alongside the potential valorization of residual algal biomass, will be explored. Additionally, challenges and potential solutions are discussed to outline future research directions of SW-integrated microalgae cultivation for carotenoids production, aligning with circular bioeconomy principles.