###### Abstract  
This study investigated anaerobically digested swine wastewater (ADSW) as a nutrient source for _Chlorella vulgaris_ FACHB-8 cultivation under mixotrophic conditions with carbon supplementation. The microalgal strain was grown in ADSW supplemented with six carbon sources, followed by concentration optimization. Under optimized conditions (20 g/L glucose), FACHB-8 demonstrated a high biomass productivity (271.31 mg/L/day) and a specific growth rate of 0.42 per day. The system achieved an 88.70% total nitrogen removal and an 82.93% total phosphorus removal. The biomass contained 45.59% lipids, 29.72% proteins, and 13.05% carbohydrates, with fatty acid methyl esters showing balanced proportions of saturated (50.77%) and unsaturated fatty acids (49.23%). These findings highlight the potential of glucose-based mixotrophic cultivation for simultaneous wastewater treatment, renewable biomass production, and value-added lipid production. This work proposes a scalable swine wastewater treatment system that synergizes bioremediation and renewable energy production via carbon-enhanced microalgae cultivation, offering a dual-functional strategy for sustainable livestock wastewater reuse. w +
Footnote †: journal: Applied sciences  
0000-0001-1001-1001-1001-1001-1001-1001-1001-1001-1001-10011-1001-1001-1001-1001-10011-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-1001-100101-1001-1001-100101-1001-1001-1001-100101-100 weight, with some species containing a lipid content of up to 75% [6]. Their rapid growth rates under optimal conditions make them promising candidates for biofuel production. Microalgae biodiesel, produced through the biochemical conversion of algal biomass [7], presents a renewable alternative to petroleum diesel with comparable combustion properties but a reduced carbon footprint [8]. However, the current production costs of microalgae biodiesel are still relatively high, primarily due to the higher cultivation expenses of algal cells [9; 10]. Therefore, cost reduction strategies focusing on low-cost nutrient sources could enhance the economic viability [11]. Recently, the use of wastewater as a nutrient source for microalgae cultivation has been suggested as a viable approach to effectively lower the production costs [12]. The microalgae-based wastewater treatment process enables microalgae to utilize nitrogen and phosphorus nutrients from low-cost wastewater for cell growth and bioremediation, simultaneously accumulating high-value bioactive compounds such as lipids [12; 13; 14; 15]. Recent advances highlight the potential of algae-bacteria symbiotic systems, where algal oxygen supports bacterial organic matter oxidation while bacterial respiration provides CO\({}_{2}\) for photosynthesis, achieving a lower energy consumption than axenic algal processes [16]. Emerging low-cost strategies seek to enhance these bioremediation and bioproduction processes through nutrient modulation (e.g., nitrogen deprivation) and organic carbon supplementation, though wastewater-derived contaminants necessitate a strain-specific adaptability for effective cultivation [11]. Microalgae can be cultivated under photoautotrophic, heterotrophic, and mixotrophic conditions [17]. Photoautotrophic cultivation relies on light-driven photosynthesis for energy conversion, while heterotrophic cultivation utilizes organic carbon substrates (e.g., simple sugars) under dark conditions. Mixotrophic cultivation synergistically combines both photosynthetic and heterotrophic modes [18; 19]. Although photoautotrophic cultivation remains the predominant commercial-scale method, due to its operational simplicity and cost-effectiveness, it presents critical limitations in wastewater treatment applications. The reduced light penetration caused by shadowing effects within the cultivation medium lead to a lower biomass productivity [20; 21].