Enhanced Acetoin Production by Serratia marcescens H32 Using Statistical Optimization and a Two-stage Agitation Speed Control Strategy

Jianan Sun,Liaoyuan Zhang,Ben Rao,Yunbin Han,Ju Chu,Jiawen Zhu,Yaling Shen,Dong-Zhi Wei 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.3

Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett–Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L)and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed,and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved. Enhanced acetoin production was carried out by Serratia marcescens H32. First, medium compositions were optimized statistically for shake flask fermentations to produce acetoin. Sucrose and corn steep liquor powder (CSLP) were identified as the most significant factors by Plackett–Burman design. The path of steepest ascent and response surface methodology were then employed to determine the optimal concentrations of the two factors. Acetoin yield was up to 41.5 g/L in flask fermentations using the optimized medium. Furthermore, the optimal medium was used to conduct fermentation experiments in a 3.7-L bioreactor. The influences of different agitation speeds on acetoin production were investigated. Based on a process analysis, a two-stage agitation speed control strategy was proposed, in which the agitation speed was controlled at 700 rpm during the first 8 h and then switched to 600 rpm. A relatively high acetoin concentration (44.9 g/L)and high acetoin productivity (1.73 g/L/h) were achieved by applying this strategy. Fed-batch fermentation based on the two-stage agitation speed control strategy was performed,and a maximum acetoin concentration of 60.5 g/L with productivity of 1.44 g/L/h was achieved.

Wake vortex interaction effects on energy extraction performance of tandem oscillating hydrofoils

Jianan Xu,Hongyu Sun,Songlin Tan 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

An energy extracting technology based on tandem oscillating hydrofoils from flow field is presented in this paper. Numerical simulation were performed to optimize the spatial arrangement for tandem oscillating hydrofoils, the position of the downstream hydrofoil relative to the wake vortex shed by the upstream hydrofoil is seen as critical. Optimized position of the two hydrofoils improves the energy extraction performance through positive interactions between the downstream hydrofoil and the wake vortices of the upstream hydrofoil, and the highest energy extraction efficiency reaches 53.8%. The downstream hydrofoil has a slight impact on the energy extraction performance of the upstream hydrofoil, and the contribution from the upstream hydrofoil is usually slightly inferior to the single hydrofoil results. Leading edge vortex (LEV) is formed and shed from the upstream hydrofoil, which is seen as critical in the energy transformation between the fluid and the energy extraction device. For different reduced frequencies, the energy extraction of a single hydrofoil is heavily influenced by the dynamics of vortex forming and shedding. The investigation was also undertaken over a wide range of kinematic parameters, including hydrofoil separation distance and reduced frequency. Results reveal that energy extraction of tandem oscillating hydrofoils shows better performance than a single hydrofoil for optimal reduced frequency and suitable hydrofoil separation distance.

Microstructure and Mechanical Properties of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr Alloy

Jianan Liu,Xiaoru Zhang,Wenxue Lv,Yumei Zhou,Daqing Fang,Xiangdong Ding,Jun Sun 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

The microstructural evolution of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr (GWZK) alloy during homogenization and subsequentaging heat-treatment and the tensile properties of the peak-aged sample at various temperatures have been investigated. Thephase transformation during homogenization, static precipitation during aging, and deformation mechanisms at 250 °C aresystematically analyzed through XRD, TEM and EBSD measurements. The peak-aged GWZK alloy has good combinationof strength and ductility at elevated temperatures owing to its high thermal stability by the LPSO phases distributed alongthe grain boundaries. The change (19 MPa) in the yield strength of peak-aged samples between RT and 250 °C is mainlyrelated to easy gliding of dislocations on the non-basal planes due to the decrease in critical resolved shear stress of slip. Two strengthening models are applied to quantitatively describe the efect of {11 −2 0}훼precipitate plates on Orowanstrengthening corresponding to RT and 250 °C. Ignoring changes in solid solution strengthening and grain boundary strengthening of the peak-aged sample caused by increasing temperature, the calculated reduction value (16.5 MPa) in macroscopicyield strength from RT (based on the basal<a>slip mode) to 250 °C (based on the pyramidal<c+a>slip mode) is in goodagreement with the measured reduction value (19 MPa).

Highly Sensitive Diagnosis of Small Hepatocellular Carcinoma Using pH-Responsive Iron Oxide Nanocluster Assemblies

Lu, Jingxiong,Sun, Jihong,Li, Fangyuan,Wang, Jin,Liu, Jianan,Kim, Dokyoon,Fan, Chunhai,Hyeon, Taeghwan,Ling, Daishun American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.32

<P>Iron oxide nanoparticle (IONP)-based magnetic resonance imaging (MRI) contrast agents have been widely used for the diagnosis of hepatic lesions. However, current IONP-based liver-specific MRI contrast agents rely on single-phase contrast enhancement of the normal liver, which is not sensitive enough to detect early stage small hepatocellular carcinomas (HCCs). We herein report i-motif DNA-assisted pH-responsive iron oxide nanocluster assemblies (termed RIAs), which provide an inverse contrast enhancemt effect to improve the distinction between normal liver and target HCC tissues. The acidic pH of the tumor microenvironment triggers the disassembly of the RIAs, which leads to a drastic decrease in their relaxivity ratio (<I>r</I><SUB>2</SUB>/<I>r</I><SUB>1</SUB>), thus converting the RIAs from a T2 to T1 contrast agent. This inverse contrast enhancement of normal liver darkening and HCC brightening under T1 imaging mode was validated on an orthotopic HCC model. Our design provides a novel strategy for the exploitation of the next-generation intelligent MRI contrast agents.</P> [FIG OMISSION]</BR>

Renal-Clearable Hollow Bismuth Subcarbonate Nanotubes for Tumor Targeted Computed Tomography Imaging and Chemoradiotherapy

Hu, Xi,Sun, Jihong,Li, Fangyuan,Li, Ruiqing,Wu, Jiahe,He, Jie,Wang, Nan,Liu, Jianan,Wang, Shuaifei,Zhou, Fei,Sun, Xiaolian,Kim, Dokyoon,Hyeon, Taeghwan,Ling, Daishun American Chemical Society 2018 Nano letters Vol.18 No.2

<P>Although metallic nanomaterials with high X-ray attenuation coefficients have been widely used as X-ray computed tomography (CT) contrast agents, their intrinsically poor biodegradability requires them to be cleared from the body to avoid any potential toxicity. On the other hand, extremely small-sized nanomaterials with outstanding renal clearance properties are not much effective for tumor targeting because of their too rapid clearance in vivo. To overcome this dilemma, here we report on the hollow bismuth subcarbonate nanotubes (BNTs) assembled from renal-clearable ultrasmall bismuth subcarbonate nanoclusters for tumor-targeted imaging and chemoradiotherapy. The BNTs could be targeted to tumors with high efficiency and exhibit a high CT contrast effect. Moreover, simultaneous radio- and chemotherapy using drug-loaded BNTs could significantly suppress tumor volumes, highlighting their potential application in CT imaging-guided therapy. Importantly, the elongated nanotubes could be disassembled into isolated small nanoclusters in the acidic tumor microenvironment, accelerating the payload release and kidney excretion. Such body clearable CT contrast agent with high imaging performance and multiple therapeutic functions shall have a substantial potential for biomedical applications.</P>

Metabolic engineering for the microbial production of marine bioactive compounds

Mao, Xiangzhao,Liu, Zhen,Sun, Jianan,Lee, Sang Yup Elsevier 2017 BIOTECHNOLOGY ADVANCES Vol.35 No.8

<P>Many marine bioactive compounds have medicinal and nutritional values. These bioactive compounds have been prepared using solvent-based extraction from marine bio-resources or chemical synthesis, which are costly, inefficient with low yields, and environmentally unfriendly. Recent advances in metabolic engineering allowed to some extent more efficient production of these compounds, showing promises to meet the increasing demand of marine natural bioactive compounds. In this paper, we review the strategies and statuses of metabolic engineering applied to microbial production of marine natural bioactive compounds including terpenoids and their derivatives, omega-3 polyunsaturated fatty acids, and marine natural drugs, and provide perspectives. (C) 2017 Elsevier Inc. All rights reserved.</P>

基于网络课程的中国大学生网络学习行为分析

张晓飞(Xiaofei Zhang),曹欣杰(Xinjie Cao),崔欧阳(Ouyang Cui),孙佳楠(Jianan Sun) YIXIN 출판사 2023 教育教学研究论丛 Vol.1 No.2

网络课程的快速发展,促进了教育教学观念转变、教学内容更新和教学方法的改革,但是这也增加了教学组织管理和学习效果测评的难度。本文基于平顶山学院学习通网络平台的《概率论与数理统计》课程监测数据,对大学生网络学习行为进行研究,分析学习平台的各类监测数据与学习效果之间的关联性以及大学生网络学习行为存在的问题,最后给出合理的改进建议,为教师对大学生的网络学习行为进行科学引导提供有力支撑,从而达到提升学习效果的目的。 The rapid development of online courses has promoted the transformation of educational and teaching concepts, the updating of teaching content and the reform of teaching methods, but it also increases the difficulty of teaching organization management and learning effect evaluation. Based on the monitoring data of “probability theory and mathematical statistics” course of Pingdingshan University’s learning network platform, this paper studies the online learning behaviors of college students, analyzes the correlation between various monitoring data on the learning platform and learning effects, and the existence of online learning behaviors of college students. Finally reasonable improvement suggestions are given to provide strong support for teachers to scientifically guide college students’ online learning behaviors, so as to achieve the purpose of improving learning effects.

Arginine-Rich Manganese Silicate Nanobubbles as a Ferroptosis-Inducing Agent for Tumor-Targeted Theranostics

Wang, Shuaifei,Li, Fangyuan,Qiao, Ruirui,Hu, Xi,Liao, Hongwei,Chen, Lumin,Wu, Jiahe,Wu, Haibin,Zhao, Meng,Liu, Jianan,Chen, Rui,Ma, Xibo,Kim, Dokyoon,Sun, Jihong,Davis, Thomas P.,Chen, Chunying,Tian, American Chemical Society 2018 ACS NANO Vol.12 No.12

<P>Ferroptosis, an iron-based cell-death pathway, has recently attracted great attention owing to its effectiveness in killing cancer cells. Previous investigations focused on the development of iron-based nanomaterials to induce ferroptosis in cancer cells by the up-regulation of reactive oxygen species (ROS) generated by the well-known Fenton reaction. Herein, we report a ferroptosis-inducing agent based on arginine-rich manganese silicate nanobubbles (AMSNs) that possess highly efficient glutathione (GSH) depletion ability and thereby induce ferroptosis by the inactivation of glutathione-dependent peroxidases 4 (GPX4). The AMSNs were synthesized <I>via</I> a one-pot reaction with arginine (Arg) as the surface ligand for tumor homing. Subsequently, a significant tumor suppression effect can be achieved by GSH depletion-induced ferroptosis. Moreover, the degradation of AMSNs during the GSH depletion contributed to <I>T</I><SUB>1</SUB>-weighted magnetic resonance imaging (MRI) enhancement as well as on-demand chemotherapeutic drug release for synergistic cancer therapy. We anticipate that the GSH-depletion-induced ferroptosis strategy by using manganese-based nanomaterials would provide insights in designing nanomedicines for tumor-targeted theranostics.</P> [FIG OMISSION]</BR>