北京棒杆菌Corynebacterium pekinense天冬氨酸激酶P184M酶动力学分析及酶学性质表征

目的研究北京棒杆菌天冬氨酸激酶(aspartate kinase,AK)184位点脯氨酸(proline,P)突变为蛋氨酸(DL-methionine,M)对酶动力学及酶学性质的影响。方法对北京棒杆菌AK家族同源序列比对,选择出高度保守且远离底物结合位点的Pro184位点,对其进行饱和定点突变,成功构建突变体P184M。结果动力学和酶学性质研究表明:P184M AK Vmax比WT(wide type)提高了5.06倍;n值为0.19,突变体由WT的正协同性变为负协同性,同时Km(mol/L)值增大;突变体AK最适pH为6.5,低于野生型最适pH 7.0;最适反应温度28℃,低于WT的30℃,适宜温度区间变窄;半衰期由WT的2.1 h降为1.2 h;金属离子、有机溶剂和抑制剂Thr+Met、Lys+Met、Thr+Lys+Met对突变株AK均表现出激活作用。结论突变体天冬氨酸激酶P184M的酶动力学性质和酶学性质改变显著,为构建高产蛋氨酸菌株提供了一定的参考依据。     

From Microbial Succinic Acid Production to Polybutylene Bio-Succinate Synthesis

A simplified and scalable one-pot process for the anaerobic production of succinic acid using a metabolically engineered Corynebacterium glutamicum strain is demonstrated. With targeted bioprocess optimization, succinic acid titer of 78 g L⁻¹ and yield of 1.41 mol_SAmol_GLC⁻¹ were achieved. Succinic acid was recovered from the neutral fermentation broth by electrochemically induced crystallization and applied for polybutylene bio-succinate synthesis using a biocompatible zinc catalyst. Except for a slight color change, the final biopolymer was comparable to the polymer from commercial precursors.     

北京棒杆菌单体天冬氨酸激酶T379N/A380C/T65I/D173G突变体酶学性质表征及工程菌构建

选取天冬氨酸激酶抑制剂赖氨酸(Lys)的结合位点苏氨酸(Thr) 379和丙氨酸(Ala) 380、底物天冬氨酸(Asp)的结合位点Thr65、既是底物也是ATP结合位点的催化活性中心Asp 173,对4个关键残基位点进行定点饱和突变.采用高通量筛选方法成功构建突变体T379N/A380C/T65I/D 173G,与野...     

表面活性剂作为糖蜜发酵谷氨酸促发剂的研究

通过对预先选择的5种表面活性剂作为谷氨酸发酵促进剂效果的初步筛选,得知五甲基三聚氧乙烯三胺和3-氯-2-羟丙基三乙基氯化铵对提高产酸率有较为明显的效果;进而从加入时间、加入剂量两个方面研究了筛选出的两种表面活性剂对谷氨酸棒状杆菌(Corynebacterium glutamicum)T-613菌体生长和谷氨酸发酵产酸的影响,从而得到最佳的发酵工艺参数。研究结果表明:发酵中后期(22 h)加入质量分数为0.5%3-氯-2-羟丙基三乙基氯化铵0.8 mL,菌种生长对数期(9 h)加入质量分数为1%的五甲基三聚氧乙烯三胺型表面活性剂2 mL,在不影响菌种生长的前提下,促使谷氨酸发酵产酸率由0.8718%提高到1.8027%,有效地提高了生产效率。     

Molecular basis of human body odour formation: insights deduced from corynebacterial genome sequences

During the past few decades, there has been an increased interest in the essential role of commensal skin bacteria in human body odour formation. It is now generally accepted that skin bacteria cause body odour by biotransformation of sweat components secreted in the human axillae. Especially, aerobic corynebacteria have been shown to contribute strongly to axillary malodour, whereas other human skin residents seem to have little influence. Analysis of odoriferous sweat components has shown that the major odour-causing substances in human sweat include steroid derivatives, short volatile branched-chain fatty acids and sulphanylalkanols. In this mini-review, we describe the molecular basis of the four most extensively studied routes of human body odour formation, while focusing on the underlying enzymatic processes. Considering the previously reported role of β-oxidation in odour formation, we analysed the genetic repertoire of eight Corynebacterium species concerning fatty acid metabolism. We particularly focused on the metabolic abilities of the lipophilic axillary isolate Corynebacterium jeikeium K411.     

谷氨酸棒杆菌生产缬氨酸的代谢工程研究进展

L-缬氨酸是人体必需的三种支链氨基酸之一,在生命代谢过程中起着非常重要的作用,因此被广泛应用于食品、医药及饲料等行业。目前,L-缬氨酸主要采用微生物发酵法生产,而谷氨酸棒杆菌是最常用的生产菌种。作者分析了谷氨酸棒杆菌中L-缬氨酸的生物合成途径和代谢调控,综述了对其进行代谢工程改造来提高L-缬氨酸产量的最新研究进展。     

生长圈法应用于选育L-异亮氨酸菌株的条件优化

生长圈测定法是L-异亮氨酸高产菌筛选育种工作中较为简单、方便、经济、有效的一种测定方法。本文对影响生长圈法测定的检测培养基加入指示菌时温度、指示菌加入量、检测板琼脂浓度、琼脂块琼脂浓度等因素进行了研究。结果得到优化方法为测定平板和琼脂块均选用基本培养基;测定平板采用上层为10mL混菌培养基,下层为10mL基本培养基的双层平板,其琼脂浓度都为1%;琼脂块的琼脂浓度为1.5%;混菌平板中指示菌培养时间为18h,加入量为4%,混菌时最佳培养基温度为55℃。