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Characterization of a High-Productivity Recombinant Strain of Zymomonas mobilis for Ethanol Production from Glucose/Xylose Mixtures

机译:从葡萄糖/木糖混合物生产乙醇的运动发酵单胞菌高产重组菌株的表征

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The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have shown that the strain ZM4(pZB5) was capable of converting a mixture of 65 g/L of glucose and 65 g/L of xylose to 62 g/L of ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of 50 g/L, an ethanol productivity of approx 5 g/(L*h), and a yield (r_(P/S)) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state (40-60 h); a slow bleed of concentrated cells may be required to overcome this problem.
机译:进一步研究了能够将葡萄糖和木糖均转化为乙醇的运动发酵单胞菌ZM4(pZB5)重组菌株的发酵特性。先前的研究表明,菌株ZM4(pZB5)能够在48小时内将65 g / L葡萄糖和65 g / L木糖的混合物转化为62 g / L乙醇,总产量为0.46 g / g 。较高的糖浓度(例如75/75 g / L)导致木糖利用不完全(80小时)。在本研究中,报道了在高糖水平下的进一步动力学评估。乙酸盐抑制研究以及对温度和pH值影响的评估表明,在应激条件下,最大的葡萄糖和木糖最大比摄取速率随着代谢解偶联的增加而增加。开发了一种高效率的系统,该系统涉及具有膜回收功能的膜生物反应器。在糖浓度约为50/50 g / L的葡萄糖/木糖,乙醇浓度为50 g / L,乙醇生产率为约5 g /(L * h)和产量(r_(P / S))的情况下达到0.50g / g。在达到初始稳定状态(40-60小时)后,发现该系统中细胞活力下降。要解决此问题,可能需要缓慢排出浓缩细胞。

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