Enhanced Acid Tolerance in Lactobacillus casei by Adaptive Evolution and Compared Stress Response during Acid Stress

Juan Zhang,Chongde Wu,Guocheng Du,Jian Chen 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.2

This study aimed to improve the acid tolerance of Lactobacillus casei Zhang and compare the stress response of the parental strain and the acid-resistant mutant during acidic conditions. Adaptive evolution was conducted for 70 days to generate acid-tolerant L. casei. The evolved mutant lb-2 exhibited more than a 60% increase in biomass as well as a 13.6 and 65.6% increase in concentrations of lactate and acetate, respectively, when cultured at pH 4.3 for 64 h. Lactic acid tolerances of the parental strain and the evolved mutant were determined. As a result,the evolved mutant showed a 318-fold higher survival rate than that of the parental strain. Physiological analysis showed that the evolved mutant exhibited higher intracellular pH (pHi), NH4+ concentration and lower inner membrane permeability than that of the parental strain during acid stress. Moreover, higher amounts of intracellular arginine and aspartate were also detected in lb-2under acid stress. Validation of the relationship between the acid tolerance and the intracellular arginine and aspartate accumulation was conducted by experiments that showed the survival of L. casei at pH 3.3 was improved 1.36-,2.10-, or 3.42-fold by the addition of 50 mM aspartate,arginine or both of them, respectively. Taken together,results presented here not only supply an effective way to select acid-resistant strains for the food industry, but also contribute to reveal the mechanisms of acid tolerance and provide new strategies to enhance the industrial utility and health-promoting properties of this species.

Multi-linear regression model for chlorine consumption by waters

Guocheng Zhu,Shanshan Zhang,Yongning Bian,Andrew S Hursthouse 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.4

In drinking water treatment, disinfection is a key step to ensure the safety of water quality and people’s health but little is known of the relationship between chlorine consumption and water matrix properties from varied sources (BWM). In this study, we measured the fluorescence from fractions of NOM (FFN) for the relevant BWM. This included the evaluation of three components: the chlorine-dependence factor (CDF) (DOC and NH₃-N), the BWM (such as NO₃⁻, NO₂⁻ and turbidity), and FFN (I-V fluorescence fractions). Multi-linear regression model was used to fit the data. Results showed that when using the CDF, BWM and FNN, in the prediction of chlorine consumption showed the (R²) values were 0.72, 0.71 and 0.41, respectively. While the FNN did not fit the model well it did enhance the model using CDF by 11.26%. The FNN is not effective in enhancement of the BWM response to the model. Combination of the CDF, BWM and FNN or that of the CDF and BWM were both effective in prediction of chlorine consumption.

Production of Cellulases by Rhizopus stolonifer from Glucose-Containing Media Based on the Regulation of Transcriptional Regulator CRE

( Yingying Zhang ),( Bin Tang ),( Guocheng Du ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.3

Carbon catabolite repression is a crucial regulation mechanism in microorganisms, but its characteristic in Rhizopus is still unclear. We extracted a carbon regulation gene, cre, that encoded a carbon catabolite repressor protein (CRE) from Rhizopus stolonifer TP-02, and studied the regulation of CRE by real-time qPCR. CRE responded to glucose in a certain range, where it could significantly regulate part of the cellulase genes (eg, bg, and cbh2) without cbh1. In the comparison of the response of cre and four cellulase genes to carboxymethylcellulose sodium and a simple carbon source (lactose), the effect of CRE was only related to the concentration of reducing sugars. By regulating the reducing sugars to range from 0.4% to 0.6%, a glucose-containing medium with lactose as the inducer could effectively induce cellulases without the repression of CRE. This regulation method could potentially reduce the cost of enzymes produced in industries and provide a possible solution to achieve the largescale synthesis of cellulases.

Enhancement of α-ketoglutarate Production in Torulopsis glabrata: Redistribution of Carbon Flux from Pyruvate to α-ketoglutarate

Dandan Zhang,Nan Liang,Zhongping Shi,Liming Liu,Jian Chen,Guocheng Du 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.2

This manuscript aimed at increasing the production of α-ketoglutarate by the multi-vitamin auxotrophic yeast Torulpsis glabrata CCTCC M202019. The carbon flux was redistributed from pyruvate to α-ketoglutarate node by manipulating the specific activity of pyruvate dehydrogenase complex (PDH), pyruvate carboxylase (PC), pyruvate decarboxylase (PDC), and α-ketoglutarate dehydrogenase complex (KGDH). By proper increase of PDH, PC, and PDC activities, α-ketoglutarate in fermentation broth could be accumulated to the levels of 17.1 g/L, 21.6 g/L, and 31.2 g/L, respectively. In addition, decrease in the specific activity of KGDH also resulted in an enhanced α-ketoglutarate synthesis. With a proposed combinational enzymes regulation strategy, the highest α-ketoglutarate concentration of 37.7 g/L was achieved This manuscript aimed at increasing the production of α-ketoglutarate by the multi-vitamin auxotrophic yeast Torulpsis glabrata CCTCC M202019. The carbon flux was redistributed from pyruvate to α-ketoglutarate node by manipulating the specific activity of pyruvate dehydrogenase complex (PDH), pyruvate carboxylase (PC), pyruvate decarboxylase (PDC), and α-ketoglutarate dehydrogenase complex (KGDH). By proper increase of PDH, PC, and PDC activities, α-ketoglutarate in fermentation broth could be accumulated to the levels of 17.1 g/L, 21.6 g/L, and 31.2 g/L, respectively. In addition, decrease in the specific activity of KGDH also resulted in an enhanced α-ketoglutarate synthesis. With a proposed combinational enzymes regulation strategy, the highest α-ketoglutarate concentration of 37.7 g/L was achieved

Enzymatic Transformation of 2-O-α-D-glucopyranosyl-L-ascorbic Acid by α-cyclodextrin Glucanotransferase from Recombinant Escherichia coli

Zichen Zhang,Jianghua Li,Long Liu,Jun Sun,Zhaozhe Hua,Guocheng Du,Jian Chen 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1

The study aimed to produce 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) via the transglycosylation reaction by α-cyclodextrin glucanotransferase (α-CGTase) from recombinant Escherichia coli with L-ascorbic acid (AA) and β-cyclodextrin (β-CD) as the substrates. Liquid chromatography-tandem mass spectrometry analysis was conducted for AA-2G identification, and the glucoamylase treatment was carried out to produce AA-2G from AA-2-oilgosaccharides. The optimal temperature and pH for the enzymatic AA-2G production were 37°C and 5.5,respectively, and the optimal α-CGTase concentration and substrate mass ratio (AA:β-CD) for AA-2G synthesis were 160 U/mL and 1:1, respectively. At these optimal process conditions, maximal AA-2G production reached 13 g/L. This is the first report regarding the process optimization of enzymatic AA-2G production by α-CGTase from recombinant E. coli. The results may be useful for the industrial scale production of AA-2G.

Effects of rolling-cutting processing parameters on micro-grooved strips forming

Baoyu Zhang,Xianqi Fan,Guocheng Shi,Yang Zhou,Di He,Wenjun Deng 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.1

High heat flux density in the micro-electronics field urges the demand for functional surface for heat transfer. Micro-grooved surface is the classical heat transfer surface because of the larger specific area and better inducement of turbulence. A novel micro-grooved surface manufacturing process, the rolling-cutting process, is proposed to produce microgrooved strips. Experiments are conducted to analyze the influence of processing parameters on the strips forming. The optimal combination of processing parameters is given to attain the micro-grooved strips with higher fins height and thinner base thickness. Additionally, the obtained strips are of three-dimensional structures with serrated bulges at the top. The difference between the material flow of serrated bulges and strip base is discussed, and the forming of serrated bulges is mainly due to inhomogeneous sinuous material flow.

Evaluation and application of constitutive promoters for cutinase production by Saccharomyces cerevisiae

Juan Zhang,Yanqiu Cai,Guocheng Du,Jian Chen,Miao Wang,Zhen Kang 한국미생물학회 2017 The journal of microbiology Vol.55 No.7

Cutinase as a promising biocatalyst has been intensively studied and applied in processes targeted for industrial scale. In this work, the cutinase gene tfu from Thermobifida fusca was artificially synthesized according to codon usage bias of Saccharomyces cerevisiae and investigated in Saccharomyces cerevisiae. Using the α-factor signal peptide, the T. fusca cutinase was successfully overexpressed and secreted with the GAL1 expression system. To increase the cutinase level and overcome some of the drawbacks of induction, four different strong promoters (ADH1, HXT1, TEF1, and TDH3) were comparatively evaluated for cutinase production. By comparison, promoter TEF1 exhibited an outstanding property and significantly increased the expression level. By fed-batch fermentation with a constant feeding approach, the activity of cutinase was increased to 29.7 U/ml. The result will contribute to apply constitutive promoter TEF1 as a tool for targeted cutinase production in S. cerevisiae cell factory.

Occurrence and control of N-nitrosodimethylamine in water engineering systems

Yongning Bian,Chuang Wang,Guocheng Zhu,Bozhi Ren,Peng Zhang,Andrew S. Hursthouse 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.1

N-nitrosodimethylamine (NDMA) is a typical nitrogen disinfection by-product, which has posed a potential threat to human health during drinking water disinfection. Because of the well-known effects of mutagenesis, carcinogenesis and teratogenesis, the high detection rate in water engineering systems (such as coagulation, membrane filtration and biological systems), and difficulty to remove, it has received wide concern in the field of water engineering systems. The NDMA is a low molecular weight hydrophilic organic substance, which is difficult to remove. Also, the mechanism for NDMA formation is also recognized to be complex, and many steps still needed to be further evaluated. Therefore, the mechanistic knowledge on NDMA formation potential and their removal processes is of particularly interest. Few papers summarize the occurrence and control of NDMA in water engineering systems. It is for this reason that the content of this paper is particularly important for us to understand and control the amount of NDMA thus reducing the threat of disinfection by-products to drinking water. Four parts including the mechanisms for the NDMA formation potential, the factors affecting the NDMA formation potential, the technologies for removal of NDMA are summarized. Finally, some definite suggestions are given.

Distributed control system architecture for deep submergence rescue vehicles

Yushan Sun,Xiangrui Ran,Guocheng Zhang,Fanyu Wu,Chengrong Du 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

The control architectures of Chuan Suo (CS) deep submergence rescue vehicle are introduced. The hardware and software architectures are also discussed. The hardware part adopts a distributed control system composed of surface and underwater nodes. A computer is used as a surface control machine. Underwater equipment is based on a multi-board-embedded industrial computer with PC104 BUS, which contains IO, A/D, D/A, eight-channel serial, and power boards. The hardware and software parts complete data transmission through optical fibers. The software part involves an IPC of embedded Vxworks real-time operating system, upon which the operation of I/O, A/D, and D/A boards and serial ports is based on; this setup improves the real-time manipulation. The information flow is controlled by the software part, and the thrust distribution is introduced. A submergence vehicle heeling control method based on ballast water tank regulation is introduced to meet the special heeling requirements of the submergence rescue vehicle during docking. Finally, the feasibility and reliability of the entire system are verified by a pool test.

Highly antibacterial electrospun double-layer mats for preventing secondary wound damage and promoting unidirectional water conduction in wound dressings

Runnan Xu,MING ZHANG,Juming Yao,YAN WANG,Yafeng Ge,Dana Kremenakova,Jiri Militky,Guocheng Zhu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.119 No.-

The efficient absorption of wound exudate and the prevention of soft tissue infection are major concernsin wound repair. Good antibacterial agents and unique wound dressing structures can effectively reducewound infection, thereby accelerating wound healing. In some double-layer asymmetric wound dressings,antimicrobial agents are incorporated in the hydrophilic layer, and only a small fraction of theantimicrobial agent penetrates the hydrophobic fibre layer towards the interior of the wound. Therefore, in this study, we chose curcumin (Cur.)/cellulose acetate (CA) as the hydrophobic inner layer. Not only does this effectively allow Cur. to make contact with the lining of the wound but it also preventsthe wound from sticking. However, the mechanical properties of a single CA/Cur. layer are not ideal. Using polyacrylonitrile as the outer hydrophilic substrate improves the fibre mat mechanical properties. In addition, to further improve the hydrophilicity, the water contact angle was reduced by introducing ahydrophilic group (2-hydroxypropyl-b-cyclodextrin, b-CD) and changing the fibre roughness (nano-TiO2). Thus, wound dressings with high biocompatibility, excellent antibacterial properties, and unidirectionalwater conduction were constructed for preventing secondary wound damage. In terms of performance, ittook 40 minutes for water to enter the hydrophilic fibre layer from the hydrophobic fibre layer (the watercontact angle decreased from 121.24 to 85.42), and it took 25 minutes for water to completely enter thefibre mats (the water contact angle decreased from 85.42-0), which is effective for draining wound exudate. In terms of antibacterial properties, the antibacterial rates of Cur. (8 wt%) against Escherichia coliand Staphylococcus aureus were 82.4% and 92.57%, respectively. The Cur./CA@PAN/b-CD/TiO2 bilayerasymmetric nanofibrous mats mimic the semipermeability of the extracellular matrix (ECM) and havehigh biocompatibility, which is effective for preventing secondary wound damage. It can be used as alow-cost, high-performance wound dressing with medical material potential.