Transcriptomics Analysis Reveals The Response Mechanism Of Chlorococcus Sp.GD To Different Concentrations Of Glucose

Microalgae wastewater treatment technology is a new type of "green technology" that can accumulate biomass as raw materials for biodiesel,aquatic feed and high value-added products while removing pollutants in wastewater.Although wastewater can provide an organic carbon source for the growth of microalgae,the carbon concentration is often insufficient or too high,which will affect the accumulation of microalgae biomass and the efficiency of wastewater treatment.In this study,a strain of Chlorococcum sp.GD cultivated with different glucose concentrations(1000-10000 mg/L)was used to explore the growth characteristics,photosynthetic activity and nutrients remove ability.Moreover,transcriptome sequencing was carried out to clarify the response mechanism of Chlorococcum sp.GD to different concentrations of glucose.The main findings were as follows:(1)The response of Chlorococcum sp.GD to different concentrations of glucose was studied.The results showed that in,the biomass accumulation and photosynthetic activity of Chlorococcum sp.GD significantly increased as the microalga was cultivated with synthetic wastewater containing 1000-4000 mg/L of glucose.The removal efficiency of COD and ammonia nitrogen was up to 92% and 92.62%,respectively.When the glucose concentration increased to 6000-10000 mg/L,the biomass accumulation of Chlorococcum sp.GD didn’t increase significantly,and pollutants removal efficiency and photosynthetic activity decreased.When the glucose concentration especially exceeded 8000 mg/L,removal efficiency of COD and ammonia nitrogen were 63% and 45.72%,respectively.Besides,the high concentration of glucose also inhibited the photosynthetic performance of Chlorococcum sp.GD.(2)Based on transcriptomics sequencing,the response mechanism of Chlorococcum sp.GD to different concentrations of glucose was preliminarily analyzed.Glucose metabolism mainly depended on the glycolysis and the pentose phosphate pathway(PPP)as the microalga was cultivated with 10000 mg/L glucose.Meanwhile,the tricarboxylic acid(TCA)cycle,oxidative phosphorylation and photosynthesis were significantly inhibited.The significant change on carbon metabolic flux caused by the increase in glucose concentration affected the synthesis of reducing power and ATP,which ultimately influenced the growth of the microalga.