Regulation of wastewater treatment by synechococcus under the influence of process parameters and exogenous signals
Efficient recycling and utilization of wastewater resources are key components in achieving carbon neutrality.The use of microalgae for wastewater treatment not only promotes the degradation of pollutants in wastewater but also converts organic matter in wastewater into biomass raw materials,further push the process of carbon neutrality.In addition,exogenously added bacterial signaling substances have shown significant effects on the growth and metabolic production of microalgae,yet there is a lack of research on the regulation of high-value product synthesis in microalgae by exogenous signaling substances.To investigate the potential of microalgae in the reduction of wastewater pollutants and the regulatory effects of exogenous microbial signaling molecules on its treatment efficiency,this study optimized the key conditions for wastewater treatment by Synechocystis sp.PCC 6 803 using Response Surface Methodology(RSM),including temperature,light intensity,and the addition of microalgae.The results showed that under optimal process parameters(temperature of 25.73℃,light intensity of 1 722.39 Lux,and Synechocystis sp.PCC 6 803 addition of 10％),the removal rates of COD(Chemical Oxygen Demand),ammonia nitrogen,total phosphorus,and total nitrogen could reach 59.57％,87.01％,50.99％,and 55.79％,respectively,and Synechocystis sp.PCC 6 803 still maintained high growth(OD680=0.448).Further,the regulatory role on wastewater resource recovery was studied by adding exogenous signaling molecules(1 000 nmol·L-1 of homoserine lactone),and it was found that the addition of homoserine lactone further promoted starch accumulation in Synechocystis sp.PCC 6 803.Through transcriptome sequencing,it was revealed that homoserine lactone regulates the starch metabolism pathway of Synechocystis sp.PCC 6 803(upregulating genes 2.4.1.18 and 3.2.1.68),affecting the synthesis of starch from ADP-glucose by influencing the 14-α-glucan branching enzyme and the glycogen operator protein GlgX homolog.This study optimized the process parameters for microalgae treatment of domestic wastewater and established the use of exogenous microbial signaling molecules to regulate microalgal carbon metabolism and effectively promote the conversion of wastewater pollutants to high-value products(starch),providing new strategies for the application of microalgae in environmental governance and renewable energy development.
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