沼液兼养培养微藻潜力及不同有机碳源影响

利用沼液培养微藻可在收获藻生物质的同时回收碳、氮、磷养分,是沼液资源化利用极具潜力的途径。与光合自养相比,兼养培养可实现藻生物量快速积累,且对光、碳利用灵活,与透光性不佳的沼液相性较好,但目前缺乏相关研究论证其可行性。本文首先选取了小球藻 Chlorella sp.、蛋白核小球藻 Chlorella pyrenoidosa、栅藻 Scenedesmus sp.,以葡萄糖为碳源利用猪粪沼液对 3株微藻进行了兼养培养。结果显示,兼养策略可在大幅强化藻生物量积累的同时协同提升沼液污染物去除。其中,Chlorella pyrenoidosa展现出最佳的生物量及养分去除优势,培养7 d生物量可达1.51 g·L^-1,为光合自养的6.12倍,沼液COD、氨氮、总氮、总磷去除率较自养分别提高了20、36、41个和32个百分点。本研究进一步考察了具备两种典型碳代谢路径的有机碳源（葡萄糖-三羧酸循环,乙酸钠-乙醛酸循环）对Chlorella pyrenoidosa沼液兼养培养的影响,发现葡萄糖相较于乙酸钠更适宜作为沼液兼养培养的有机碳源,且葡萄糖浓度与利用效率呈负相关,1 g·L^-1葡萄糖浓度条件下Chlorella pyrenoidosa具有最高的单位有机碳生物量产率。此外,兼养微藻通过代谢葡萄糖可协同提升光合性能,使PSⅡ最大量子产量、实际量子产量、调节性能量耗散量子产量等维持较高水平,既弥补了沼液弱透光下光能不足,也强化了持续光照后的光系统损伤恢复机制。因此,本研究认为以添加1 g·L^-1葡萄糖的沼液兼养培养Chlorella pyrenoidosa是克服沼液养藻光衰减等不利因素,强化微藻生物量产量及养分回收效率的有效方式,在畜禽养殖场沼液生物消纳与资源化利用方面有较好的应用前景。

Potential of mixotrophic microalgal cultivation in biogas slurry and the effects of using various organic carbon sources

Cultivating microalgae in biogas slurry can recover carbon, nitrogen, and phosphorus nutrients while producing algal biomass. This approach offers a promising way to utilize biogas slurry resources. Mixotrophic culture, compared to photosynthetic autotrophy, can rapidly accumulate algal biomass, flexibly use light and carbon, and is well-suited to biogas slurry with poor light transmittance. Despite its potential, there is currently limited research demonstrating its feasibility. This study initially selected Chlorella sp., Chlorella pyrenoidosa, and Scenedesmus sp., using glucose as the carbon source to culture these microalgal strains in pig manure biogas slurry. The results indicated that the mixotrophic strategy significantly enhanced algal biomass accumulation and synergistically improved pollutant removal from biogas slurry, showing promising feasibility. Chlorella pyrenoidosa exhibited the greatest advantages in biomass production and nutrient removal, achieving 1.51 g·L^-1 after 7 days of cultivation, which is 6.12 times the value of photoautotrophy. It also increased the removal rates of COD, NH+ 4-N, TN, and TP by 20%, 36%, 41%, and 32%, respectively, compared with autotrophy. Additionally, in this study we examined the impacts of organic carbon sources on the mixed culture Chlorella pyrenoidosa in biogas slurry, focusing on two typical carbon metabolism pathways（glucose-tricarboxylic acid cycle and sodium acetate-glyoxylic acid cycle）. These findings suggested that glucose, especially at a concentration of 1 g·L^-1, was more suitable than sodium acetate as an organic carbon source for biogas slurry, showing a negative correlation with utilization efficiency. Moreover, Chlorella pyrenoidosa maintained high levels of photosynthetic performance by metabolizing glucose, maintaining the maximum quantum yield of PSII, actual quantum yield, regulatory energy dissipation quantum yield, and others, at a high level, which not only makes up for the lack of light energy under weak light transmission of biogas slurry, but it also strengthened the photosystem damage recovery mechanism after continuous illumination. The findings suggest that cultivating Chlorella pyrenoidosa in biogas slurry with the addition of 1 g·L^-1 glucose is an effective way to overcome unfavorable factors such as the light attenuation of algae culture in biogas slurry and enhance microalgae biomass production and nutrient recovery. These findings have good application prospects in livestock and poultry breeding, biological consumption, and resource utilization of on-site biogas slurry.