利用农业废弃物发酵生产D-乳酸

利用农业废弃物玉米芯酶解液替代葡萄糖作为碳源,棉籽粕替代酵母膏作为氮源发酵生产D-乳酸。结果表明:在初始还原糖质量浓度为100 g/L(葡萄糖88.5 g/L,木糖11.5 g/L)、棉籽粕3.5 g/L、每升发酵体积添加3 U的中性蛋白酶以及pH 6.5的情况下,采取补料发酵措施,菌株Sporolactobacillus sp.YBS1-5在90 h内产生了111.8 g/L的D-乳酸,糖酸转化率为87%,光学纯度达98%以上,生产强度达1.24 g/(L·h)。本文提供了一种利用农业废弃物发酵产D-乳酸的新途径。     

大肠杆菌琥珀酸和乙酸合成途径的删除及其重组菌株的D-乳酸发酵

菌株CICIM B0013-030 (B0013,ack-pta,pps,pflB) 可积累D-乳酸作为主要发酵产物,然而副产物琥珀酸和乙酸的含量分别高达乳酸的11.9％和7.1％。为构建副产物含量低的产D-乳酸重组大肠杆菌菌株,本研究删除了菌株B0013-030的琥珀酸 (frdA) 和乙酸 (tdcDE) 合成途径,并考察了重组菌株在摇瓶和发酵罐中经两阶段发酵 (好氧生长菌体和厌氧发酵产酸) 利用葡萄糖发酵D-乳酸的性能。结果表明,分别构建含有frdA::difGm和tdcDE::difGm突变盒的重组质粒,并利用Red重组系统将突变盒整合于染色体上的目的基因,再利用Xer重组系统去除抗生素抗性基因,依次获得了重组菌株B0013-040B (B0013-030,frdA) 和B0013-050B (B0013-040B,tdcDE)。摇瓶发酵结果表明,frdA基因的删除使得菌株B0013-040B副产物琥珀酸的含量降低了80.8％;在7 L发酵罐中进行乳酸发酵,菌株B0013-040B的D-乳酸产量达114.5 g/L,光学纯度大于99.9％,但仍积累1.0 g/L琥珀酸和5.4 g/L乙酸。进一步删除了tdcD和tdcE基因的菌株B0013-050B,在7 L发酵罐中生产111.9 g/L D-乳酸,乙酸和琥珀酸的合成量分别降低为0.4 g/L,其他副产物含量也维持较低水平,表明该菌株具有较优良的D-乳酸发酵性能。     

菊糖芽孢乳杆菌DS2-18中试规模的D-乳酸发酵研究

研究了菊糖芽孢乳杆茵DS2的突变株DS2-18在中试规模的D-乳酸发酵.在容积为300L自控发酵罐中,DS2-18茵在合适的发酵条件下,即培养基组成(g/L):葡萄糖120,玉米浆8,蛋白胨6,豆粕水解液100,接种量8%(v/v),发酵温度40℃,以轻质碳酸钙作为中和剂调pH 5～6,发酵期间交替不通气和通气,发酵6...     

重组大肠杆菌利用木糖发酵产高纯度L-乳酸

对重组大肠杆菌JH16利用木糖产高纯度的三一乳酸进行研究。通过无氧管驯化EscherwhiacdiJH12菌株得到E．coliJH16,驯化后的菌株茵体浓度提高了31％,乙酸积累减少了43％;在摇瓶中考察不同Mg2＋浓度对EcoliJHl6产三一乳酸的影响,确定最适Mg2＋质量浓度为0．25g/L;EcoEJH16以60g/L木糖为C源,在7L全自动发酵罐中添加0．25g／LMg2＋,乳酸积累量提高了18％,达38．18g/L,乳酸纯度高达95％;E．coliJH16在30g／L木糖和30g／L葡萄糖混合C源中,优先利用葡萄糖,当葡萄糖质量浓度低于1．56g/L后,菌体开始利用木糖进行乳酸发酵,最终得到39g／L乳酸。     

菊糖芽孢乳杆菌利用麸皮水解液发酵生产D-乳酸

考察菊糖芽孢乳杆菌YBS1-5利用麸皮的水解液发酵生产D-乳酸的性能。首先研究了不同蛋白酶对麸皮中蛋白组分的水解效率,优选酸性蛋白酶并对其进行水解工艺的优化,最终其水解液中的含氮量为4.6 g/L,水解效率为85.8%。对酸性蛋白酶的水解液残渣进行稀酸预处理后,利用纤维素酶对其进行酶解。通过批次补料酶解,水解液中的还原糖质量浓度达141.2 g/L,其中葡萄糖质量浓度为138.1 g/L、木糖质量浓度为1.4 g/L。利用麸皮的蛋白酶水解液和纤维素酶水解液替代葡萄糖和酵母粉发酵制备D-乳酸。在96 h内,D-乳酸产量达99.5 g/L,生产速率达1.04 g/(L·h),转化率89.1%。     

2,3-丁二醇生产菌株生产能力的比较和培养基优化

对5株克雷伯氏肺炎杆菌 (包括两株乳酸途径被敲除的工程菌株) 发酵生产2,3-丁二醇能力进行了比较,其中K. pneumonia HR521 LDH (乳酸合成途径中ldhA基因被敲除) 具有最佳的发酵性能。通过正交试验优化了其发酵培养基的主要组分,优化后的培养基组成为：葡萄糖 90 g/L,(NH4)2HPO4 3 g/L,玉米浆 (CLSP) 6 g/L,乙酸钠 5 g/L,KCl 0.4 g/L,MgSO4 0.1 g/L,FeSO4·7H2O 0.02 g/L,MnSO4 0.01 g/L。在优化后的发酵培养基中进行摇瓶发酵,24 h发酵乙偶姻和2,3-丁二醇的终浓度为37.46 g/L,比未优化前增加了10 g/L,2,3-丁二醇得率达到了理论得率的90.53％,生产强度1.56 g/(L·h),检测不到副产物乳酸的生成,利于后提取工艺的进行和工业生产的应用。     

戊糖乳杆菌发酵产乳酸及高产菌株诱变选育

戊糖乳杆菌(Lactobacillus pentosus)是能利用木质纤维素水解液发酵产乳酸的潜力菌株,发酵条件优化与高产菌株的选育是提高乳酸产量的重要手段。通过单因素试验、Plackett-Burman设计与响应面试验,对戊糖乳杆菌ATCC 8041产乳酸的发酵培养基及发酵条件进行了优化。结果表明,该菌株发酵培养基的最佳组合为葡萄糖93.11 g/L、酵母浸粉5.19 g/L、碳酸钙29.43 g/L、蛋白胨10.00 g/L、Na2HPO4·12H2O 5.00 g/L、Mg SO4 0.20 g/L、Mn SO4 50 mg/L;最佳发酵条件为37℃、p H6.5、接种量6%、装液量80%。在此优化条件下,该菌株发酵产乳酸为54.12 g/L。进一步以戊糖乳杆菌ATCC 8041为出发菌株,通过原生质体进行紫外诱变,经多重筛选,最终获得一株遗传稳定性好的高产乳酸突变株,命名为戊糖乳杆菌Lactic UVC-02,由中国典型培养物保藏中心保存,注册号为CCTCC M 2013209。该突变株Lactic UVC-02经葡萄糖发酵,乳酸产量达64.17 g/L,比出发菌株ATCC 8041(54.12g/L)提高18.6%。     

产D-乳酸重组大肠杆菌ptsG基因的敲除及其混合糖同步发酵

为构建能够同时高效利用五碳糖和六碳糖发酵产D-乳酸的重组大肠杆菌工程菌,以能高效利用五碳糖发酵产D-乳酸的大肠杆菌工程菌E.coli JH13为出发菌株,通过Red同源重组技术敲除葡萄糖跨膜转运基因pts G。实验结果表明,pts G缺陷菌株E.coli JH15在10%混合糖(5%葡萄糖和5%木糖)培养基中发酵,可同时利用五碳糖和六碳糖以完成发酵;而对照菌葡萄糖消耗完才利用木糖,发酵结束还有18 g/L木糖残留;JH15乳酸产量为83.04 g/L,相比于对照菌株提高了25.86%;在稻草秸秆水解液中发酵,JH15同时利用葡萄糖、木糖和L-阿拉伯糖,乳酸产量为25.15 g/L,转化率为86.42%。JH15作为能利用混合糖同步发酵产D-乳酸的大肠杆菌工程菌,它的成功构建为利用廉价的木质纤维素水解物为原料发酵生产D-乳酸提供参考依据。     

丁酸梭杆菌发酵甘油制备1,3-丙二醇的研究

本研究采用丁酸梭芽孢杆菌(Clostridium butyricum)从甘油发酵制备1,3—丙二醇。该发酵需厌氧培养,发酵培养基为：甘油6％,葡萄糖1％,玉米浆2％,(NH4)2SO40．2％。发酵温度为34℃,pH为6．5～7。在最佳条件下,发酵50h可产1,3—丙二醇40．7g／L,甘油摩尔转化率达68％。     

羰基还原酶产生菌SW2026的产酶条件及其不对称催化还原4＇-氯苯乙酮

以4＇-氯苯乙酮为模型底物,对筛选得到的Candida krusei SW2026的羰基还原酶产酶条件进行研究。结果表明：适宜的发酵培养基组成为甘油50g/L,玉米浆20g／L,KH2PO4 4g／L,MgSO4·7H2O 1．5g／L;适宜的培养条件为温度30℃,初始pH6,摇床转速200r／min,发酵周期48h。在产酶发酵条件下培养的湿细胞对4＇-氯苯乙酮进行不对称还原反应,产物（S）-4＇-氯-α-苯乙醇的产率最高达88．56％,e．e．值稳定在87％左右。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.