Limin Yang

Food processing wastewater (FPW) poses significant environmental risks due to its high nutrient load yet offers untapped potential as a low-cost feedstock for high-value compound production. This review critically evaluates the valorization of FPW for astaxanthin production through the mixotrophic fermentation of microalgae. Key microalgal species (e.g., Haematococcus pluvialis and Chromochloris zofingiensis) effectively remediate nutrients (nutrients removal of up to 100%) while synthesizing astaxanthin under stress-inducing conditions, such as nutrient starvation, salinity, and oxidative stress. Advanced strategies, such as two-stage cultivation, nutrient profile adjustment, and microbial co-cultivation, which could enhance astaxanthin yields and wastewater treatment efficiency were reviewed comprehensively. The resulting astaxanthin-rich biomass demonstrates multifunctional benefits in animal feed, improving meat quality, immunity, growth, and shelf life. However, this review identifies some challenges, including wastewater management risks, low digestibility of microalgae biomass, and astaxanthin instability during feed processing, which should be addressed properly in real-world applications. This integrated approach aligns with circular bio-economy principles, transforming FPW from an environmental liability into a resource for sustainable biotechnology.

Introduction: Endogenous algal consortia were cultivated in a recirculating aquaculture system to recover nutrients from wastewater and facilitate carbon sequestration.Methods: This study investigated the microbial community composition of the algal consortia, the roles of algae and associated microorganisms, the optimization of operational parameters, and the carbon emissions of the pilot-scale system.Results and discussion: The results showed that filamentous algae, particularly Schizomeris sp., are the dominant species in algal consortia. The interaction of algae and bacteria enhanced biomass production (0.90 g/L) and improved TOC removal efficiency (80.38%), demonstrating the excellent performance of algal consortia in wastewater treatment. In laboratory research, under optimal conditions, the carbon retention of algae-based aquaculture wastewater treatment reached 185.20 mg carbon/L of wastewater. In the 150-day pilot-scale experiment, 50.76 kg of carbon (feed) was input into the aquaculture system, while 11.50 kg of carbon was outputted as fish product, and algae biomass containing 39.27 kg of carbon was produced, resulting in an aquaculture process with net-zero carbon emission. The results of this study will provide a theoretical basis and practical strategies for the development of an eco-friendly aquaculture mode toward carbon neutrality.

Microalgae, with their unparalleled capabilities for sunlight-driven growth, CO₂ fixation, and synthesis of diverse high-value compounds, represent sustainable cell factories for a circular bioeconomy. However, industrial deployment has been hindered by biological constraints and the inadequacy of conventional genetic tools. The advent of CRISPR-Cas systems initially provided precise gene editing via targeted DNA cleavage. This review argues that the true transformative potential lies in moving decisively beyond cutting to harness CRISPR as a versatile synthetic biology “Swiss Army Knife”. We synthesize the rapid evolution of CRISPR-derived tools—including transcriptional modulators (CRISPRa/i), epigenome editors, base/prime editors, multiplexed systems, and biosensor-integrated logic gates—and their revolutionary applications in microalgal engineering. These tools enable tunable gene expression, stable epigenetic reprogramming, DSB-free nucleotide-level precision editing, coordinated rewiring of complex metabolic networks, and dynamic, autonomous control in response to environmental cues. We critically evaluate their deployment to enhance photosynthesis, boost lipid/biofuel production, engineer high-value compound pathways (carotenoids, PUFAs, proteins), improve stress resilience, and optimize carbon utilization. Persistent challenges—species-specific tool optimization, delivery efficiency, genetic stability, scalability, and biosafety—are analyzed, alongside emerging solutions and future directions integrating AI, automation, and multi-omics. The strategic integration of this CRISPR toolkit unlocks the potential to engineer robust, high-productivity microalgal cell factories, finally realizing their promise as sustainable platforms for next-generation biomanufacturing.