Nisin是一种由乳酸链球菌产生的细菌素,因其对李斯特氏菌、梭状芽胞杆菌、葡萄球菌等有抗菌作用且对人安全,已被美国食品药品监管局(Food Drug Administration,FDA)批准用作食品添加剂。然而野生型乳酸链球菌Nisin产量低,生产成本高,是...Nisin是一种由乳酸链球菌产生的细菌素,因其对李斯特氏菌、梭状芽胞杆菌、葡萄球菌等有抗菌作用且对人安全,已被美国食品药品监管局(Food Drug Administration,FDA)批准用作食品添加剂。然而野生型乳酸链球菌Nisin产量低,生产成本高,是限制其推广应用的重要因素。近年来,通过对Nisin生产菌株的基因改造和发酵工艺优化,其产量得到了显著提高,但仍无法满足人们对Nisin日益增长的需要。本文综述了Nisin的生物合成途径、近几年改造乳酸链球菌生产Nisin取得的成果和面临的问题。展开更多
The thermodynamics of Mo-O- C and Ca-Mc-O-C systems was studied in order to understand the carbothermic reduction of molybdenum trioxide, and kinetic studies were also carried out by means of thermogravimetrie analysi...The thermodynamics of Mo-O- C and Ca-Mc-O-C systems was studied in order to understand the carbothermic reduction of molybdenum trioxide, and kinetic studies were also carried out by means of thermogravimetrie analysis under argon atmosphere with a heating rate of 10 ℃/min. Subsequently, reaction products at various temperatures were identified by X-ray diffraction （XRD） and the results confirmed the previous thermodynamics analysis. Mean- while, it was found that intermediate products MoO2 and CaMoO4 appeared in the process of carbothermic reduction of MoO3 with or without CaO, which were subsequently reduced to Mo or molybdenum carbide. An experimentally determined reaction mechanism was proposed and discussed. The reduction reaction of MoO3 with carbon could be divided into two stages. The first stage includes the direct reaction between MoO3 and carbon and the carbon gasifica- tion reaction. The second stage is the gas-solid reaction between CO and MoO2, and the diffusion of gases through the surface of MoO2 determines the overall reaction rate. The activation energies of the mixtures with or without CaO were estimated to be 56.6 and 52.9 kJ/mol, respectively.展开更多
文摘Nisin是一种由乳酸链球菌产生的细菌素,因其对李斯特氏菌、梭状芽胞杆菌、葡萄球菌等有抗菌作用且对人安全,已被美国食品药品监管局(Food Drug Administration,FDA)批准用作食品添加剂。然而野生型乳酸链球菌Nisin产量低,生产成本高,是限制其推广应用的重要因素。近年来,通过对Nisin生产菌株的基因改造和发酵工艺优化,其产量得到了显著提高,但仍无法满足人们对Nisin日益增长的需要。本文综述了Nisin的生物合成途径、近几年改造乳酸链球菌生产Nisin取得的成果和面临的问题。
基金Item Sponsored by Science and Technology Achievement Special Foundation of Jiangsu Province of China(BA2010139)
文摘The thermodynamics of Mo-O- C and Ca-Mc-O-C systems was studied in order to understand the carbothermic reduction of molybdenum trioxide, and kinetic studies were also carried out by means of thermogravimetrie analysis under argon atmosphere with a heating rate of 10 ℃/min. Subsequently, reaction products at various temperatures were identified by X-ray diffraction （XRD） and the results confirmed the previous thermodynamics analysis. Mean- while, it was found that intermediate products MoO2 and CaMoO4 appeared in the process of carbothermic reduction of MoO3 with or without CaO, which were subsequently reduced to Mo or molybdenum carbide. An experimentally determined reaction mechanism was proposed and discussed. The reduction reaction of MoO3 with carbon could be divided into two stages. The first stage includes the direct reaction between MoO3 and carbon and the carbon gasifica- tion reaction. The second stage is the gas-solid reaction between CO and MoO2, and the diffusion of gases through the surface of MoO2 determines the overall reaction rate. The activation energies of the mixtures with or without CaO were estimated to be 56.6 and 52.9 kJ/mol, respectively.
