Effect of Different Mixed Light-Emitting Diode Light Wavelengths on Co2 Absorption from Biogas and Nutrient Removal from Biogas Slurry by Microalgae and Fungi Induced Using Strigolactone and Endophytic Bacteria

In this study, biogas and biogas slurry were simultaneously treated using two symbiotic systems: Chlorella vulgaris-Ganoderma lucidum-S395-2 (endophytic bacteria) and Scenedesmus obliquus-G. lucidum-S395-2. The influence of different mixed illumination (red and blue) intensity ratios on the algal symbionts' extracellular carbonic anhydrase activities was investigated, as well as the rates of microalgal growth and photosynthesis. The treatment performance was simultaneously assessed in terms of the efficiency of organic matter or nutrient removal and the level of CO2 absorption. The results indicated that red-blue light combinations with an intensity ratio of 5:5 were optimal. When comparing the performance of the two symbiotic systems, the C. vulgaris-G. lucidum-S395-2 symbiont co-culture system achieved significantly improved photosynthetic rates, biomass growth, and treatment effects. Under the optimal treatment conditions, the organic matter and nutrient removal rates were 81.06% +/- 7.06% for chemical oxygen demand, 82.32% +/- 7.18% for total nitrogen, and 82.98% +/- 7.26% for total phosphorus. In addition, the rate of CO2 removal from biogas was 63.38% +/- 5.35%. Practitioner Points The red and blue light intensity ratio of 5:5 showed the best removal performance.C. vulgaris-G. lucidum-S395-2 system obtained the best photosynthetic performance.The carbonic anhydrase activity had positive effects on CO2 removal performance.