基于聚磷菌群(PAOs)内聚磷酸盐推动的PHB的合成与积累动力学及机理研究

Sequencing batch reactor activated sludge process (SBR A) is an original way to produce poly-β-hydroxybutyrate (PHB) which is a reverse process similar to biodephosphorization. This process is derived from excess sludge at the end of aerobic phase of biodephosphorization and utilizes the polyphosphates and glycogens in the polyphosphate accumulationg bacteria (PAO) as energy and reducing power, synthesizing acetates into PHB under anaerobic condition. This technology is advantage over traditional process in two aspects: (1) overcoming the low productivity as well as large consumption of saccharide materials and energy during single microorganism fermentation; (2) avoiding the contaminant risk of PHB residuals during the extracting process from the cultures of mixed micro-species fermentation or dephosphorization sludge under anaerobic phase. This project plans to optimize the SBR A and achieve following goals: (1) obtain highly effective and stable polyphosphate accumulationg bacteria community; (2) deduce the fundamental equation on PHB formation according to the conversion relationships among acetates, glycogens, polyphosphates and PHB, namely the quantitative coefficients involved in transformation of intracellular components; (3) establish, testify and modify the kinetic equation on acetates absorption, phosphates release and PHB synthesis based on conversion rate and specific rate of the vital substances during one anaerobic cycle; (4) partially reveal the reactive mechanisms, including phosphates release and ATP formation under anaerobic condition, glycogen consumption and NADPH formation, especially the starting, coupling, signal transmission together with spatio-temporal order between acetate absorption and PHB synthesis. This work will contribute to the further technical improvements and theoretical basis of management and control for SBR A.

以生物脱磷好氧段末端剩余污泥为起点，利用污泥聚磷菌群中的聚磷、糖原为能源、还原力原,厌氧驱动乙酸合成PHB，该工艺（SBR A）类似生物脱磷的逆过程,是生产PHB的一个新思路。其绕过纯种发酵产率低、消耗糖质物料、耗能大；混合菌群直接发酵废水或脱磷厌氧段污泥直接提取PHB污染物残留风险等问题。本项目拟优化建立该工艺，获得高效稳定的聚磷菌群；研究乙酸、糖原、聚磷和PHB等物质间转化的量式关系，推导出聚磷转化乙酸生成PHB的基本方程式即细胞内各组分之间转化的计量系数；研究一个厌氧期内乙酸吸收、释磷和PHB合成的速率及比速率间的关系，建立乙酸吸收、释磷、PHB合成动力学方程并验证和修正；利用该方程可揭示或部分揭示厌氧释磷与ATP形成，糖原消耗与NADPH形成，HAc吸收与PHB合成相互间的启动、偶联、信号传递和时空顺序等机理。为进一步改进、完善该工艺，提升工艺管理、控制水平提供理论基础。

聚羟基丁酸（PHB）是由聚磷菌合成的生物聚酯，在C源过多，N、P、S等受限时，会利用碳源在胞内合成PHB并积累。本项目取自污水处理厂的剩余污泥经过活性恢复、聚磷菌驯化和高产PHB聚磷菌的富集获取具高产PHB能力的聚磷菌群。通过自制A/O SBR反应器交替循环进行污泥活性恢复，系统COD去除率达到80%以上且维持5天共20周期，周期污泥生长量也维持稳定，沉降性能良好，并有一定除磷能力证明剩余污泥活性恢复成功；然后在污泥活性恢复后通过调整周期运行过程中COD浓度，N源浓度，分为三步，各20周期。第一步COD/N/P=450/45/15，第40周期COD去除率为86.98%，除磷率为43.00%；第二步COD/N/P=600/60/15，第60周期COD去除率为90.6%，除磷率为69.66；第三步COD/N/P=600/30/15，第80周期COD去除率为90.35%，除磷率为85.12%，厌氧末端剩余污泥中PHB浓度为410.08 mg/L。富集具有高产PHB能力的聚磷菌分为四步,第一步等比增加COD、N，COD浓度提升至1200 mg/L，COD/N/P=1200/60/15，第100周期COD去除率为94.94%，除磷率为76.94%，厌氧末端PHB/MLSS为18.89%；第二步COD/N/P=1200/30/15，第120周期COD去除率为94.86%，除磷率为62.78%，厌氧末端PHB/MLSS为25.29%;第三步COD/N/P=1200/24/15，第140周期COD去除率为94.41%，除磷率为53.52%，厌氧末端PHB/MLSS为28.95%；第四步COD/N/P=1200/12/15，第140周期COD去除率为94.44%，除磷率为33.10%，厌氧末端PHB/MLSS为35.65%。本项目通过研究乙酸、糖原、聚磷和PHB等物质间转化的量式关系，推导出聚磷转化乙酸生成PHB的基本方程式；研究一个厌氧期内乙酸吸收、释磷和PHB合成的速率及比速率间的关系，建立乙酸吸收、释磷、PHB合成动力学方程并验证和修正；揭示厌氧释磷与ATP形成，糖原消耗与NADPH形成，HAc吸收与PHB合成相互间的启动、偶联、信号传递和时空顺序等机理。为进一步改进、完善该工艺，提升工艺管理、控制水平提供理论基础。