Construction of an Efficient Mutant Strain of Trichosporonoides oedocephalis with HOG1 Gene Deletion for Production of Erythritol

( Liangzhi Li ),( Tianyi Yang ),( Weiqiang Guo ),( Xin Ju ),( Cuiying Hu ),( Bingyu Tang ),( Jiaolong Fu ),( Jingsheng Gu ),( Haiyang Zhang ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.4

The mitogen-activated protein kinase HOG1 (high-osmolarity glycerol response pathway) plays a crucial role in the response of yeast to hyperosmotic shock. Trichosporonoides oedocephalis produces large amounts of polyols (e.g., erythritol and glycerol) in a culture medium. However, the effects of HOG1 gene knockout and environmental stress on the production of these polyols have not yet been studied. In this study, a To-HOG1 null mutation was constructed in T. oedocephalis using the loxP-Kan-loxP/Cre system as replacement of the targeted genes, and the resultant mutants showed much smaller colonies than the wild-type controls. Interestingly, compared with the wild-type strains, the results of shake-flask culture showed that To-HOG1 null mutation increased erythritol production by 1.44-fold while decreasing glycerol production by 71.23%. In addition, this study investigated the effects of citric acid stress on the T. oedocephalis HOG1 null mutants and the wild-type strain. When the supplementation of citric acid in the fermentation medium was controlled at 0.3% (w/v), the concentration of erythritol produced from the wild-type and To-HOG1 knockout mutant strains improved by 18.21% and 21.65%, respectively.

Scattering Correction for Image Reconstruction in Flash Radiography

LIANGZHI CAO,Mengqi Wang,Hongchun Wu,Zhouyu Liu,Yuxiong Cheng,Hongbo Zhang 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.4

Scattered photons cause blurring and distortions in flash radiography, reducing the accuracy of image reconstruction significantly. The effect of the scattered photons is taken into account and an iterative deduction of the scattered photons is proposed to amend the scattering effect for image restoration. In order to deduct the scattering contribution, the flux of scattered photons is estimated as the sum of two components. The single scattered component is calculated accurately together with the uncollided flux along the characteristic ray, while the multiple scattered component is evaluated using correction coefficients pre-obtained from Monte Carlo simulations.The arbitrary geometry pretreatment and ray tracing are carried out based on the customization of AutoCAD. With the above model, an Iterative Procedure for image restORation code, IPOR, is developed. Numerical results demonstrate that the IPOR code is much more accurate than the direct reconstruction solution without scattering correction and it has a very high computational efficiency.

Enhancement of Ribitol Production during Fermentation of Trichosporonoides oedocephalis ATCC 16958 by Optimizing the Medium and Altering Agitation Strategies

Liangzhi Li,Huaxing Zhang,Jiaolong Fu,Chao Hu,Yayue Zheng,Yexian Qiu 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.2

To maximize the productivity of ribitol, which is an important starting material for the production of one expensive rare sugar, L-ribose, the effects of culture medium and agitation speed on cell growth as well as on the productivity of ribitol were thoroughly investigated in a 7 L fermentor. The maximum volumetric productivity,0.322 g/L/h of ribitol, were obtained at an initial glucose concentration of 200 g/L in a batch culture. Based on the optimum glucose concentration, the ribitol yield conversed from glucose was up to 0.193 g/g when 1% yeast extract was used as a nitrogen source. When the agitation speed was maintained at 200 rpm, the ribitol concentration of 38.60 g/L was collected after 120 h of cultivation time. Additionally, the scheme of two-phase agitation and glucose infusion was employed. To begin, in the first 24 h of fermentation, a high agitation rate at 350 rpm and the initial glucose concentration of 50 g/L were applied, and the biomass concentration of 25.50 g/L was achieved at 36 h of incubation; whereas this value was observed until 60 h in the former batch fermentation methods. Then, in the second phase, with the agitation speed reduced to 150 rpm and the infusion amount of glucose controlled at 150 g/L,the yield of ribitol reached to 65.00 g/L in two-phase agitation fermentation and was 1.68 fold of that obtained in one-stage batch fermentation. To our knowledge, this study first demonstrates its significant effectiveness in improving ribitol production with the application of Trichosporonoides oedocephalis ATCC 16958.

SCATTERING CORRECTION FOR IMAGE RECONSTRUCTION IN FLASH RADIOGRAPHY

Cao, Liangzhi,Wang, Mengqi,Wu, Hongchun,Liu, Zhouyu,Cheng, Yuxiong,Zhang, Hongbo Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.4

Scattered photons cause blurring and distortions in flash radiography, reducing the accuracy of image reconstruction significantly. The effect of the scattered photons is taken into account and an iterative deduction of the scattered photons is proposed to amend the scattering effect for image restoration. In order to deduct the scattering contribution, the flux of scattered photons is estimated as the sum of two components. The single scattered component is calculated accurately together with the uncollided flux along the characteristic ray, while the multiple scattered component is evaluated using correction coefficients pre-obtained from Monte Carlo simulations.The arbitrary geometry pretreatment and ray tracing are carried out based on the customization of AutoCAD. With the above model, an Iterative Procedure for image restORation code, IPOR, is developed. Numerical results demonstrate that the IPOR code is much more accurate than the direct reconstruction solution without scattering correction and it has a very high computational efficiency.

The JFNK method for the PWR's transient simulation considering neutronics, thermal hydraulics and mechanics

He, Qingming,Zhang, Yijun,Liu, Zhouyu,Cao, Liangzhi,Wu, Hongchun Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.2

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.

Improvement of FK506 Production by Selection of 4-Aminobutyric Acid-tolerant Mutant and Optimization of its Fermentation Using Response Surface Methodology

Tianyi Yang,Jiaojiao Li,Liangzhi Li,Haiyang Zhang,Jing Ma,Zhi Chen,Cuiying Hu,Xin Ju,Jiaolong Fu 한국응용생명화학회 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.6

Tacrolimus (FK506), a 23-membered polyketidemacrolide with immunosuppressant activity, can be produced byStreptomyces tsukubaensis. We studied a variety of mutant strainsof S. tsukubaensis for the microbial production of FK506. Thebest strain (CZ-19) was obtained from the parent strain LLZ-1 bynitrosoguanidine mutation and 4-Aminobutyric acid (FK506precursor structure analogs) adaption. In the shake-flask experiments,titer of FK506 by CZ-19 was 532.44 mg/L, increased by 65.13%compared to that of the parent strain. Through single factorexperiments and response surface methodology, we furtheroptimized the medium for improved FK506 production by CZ-19in shake flask culture. The optimal medium for enhanced FK506production was as follows: 17.19 g/L corn starch, 21.78 g/Lglucose, 8.06 g/L peptone, and 18.98 mg/L 4-aminobutyric acid. The predicted FK506 titer was 906.49 mg/L, and the experimentaldata confirmed the validity of the model. The present studydemonstrates that S. tsukubaensis CZ-19 is a promising strain forindustrial production of FK506.

Improvement of FK506 Production by Selection of 4-Aminobutyric Acid-tolerant Mutant and Optimization of its Fermentation Using Response Surface Methodology

Yang, Tianyi,Li, Jiaojiao,Li, Liangzhi,Zhang, Haiyang,Ma, Jing,Chen, Zhi,Hu, Cuiying,Ju, Xin,Fu, Jiaolong 한국응용생명화학회 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.6

Tacrolimus (FK506), a 23-membered polyketide macrolide with immunosuppressant activity, can be produced by Streptomyces tsukubaensis. We studied a variety of mutant strains of S. tsukubaensis for the microbial production of FK506. The best strain (CZ-19) was obtained from the parent strain LLZ-1 by nitrosoguanidine mutation and 4-Aminobutyric acid (FK506 precursor structure analogs) adaption. In the shake-flask experiments, titer of FK506 by CZ-19 was 532.44 mg/L, increased by 65.13% compared to that of the parent strain. Through single factor experiments and response surface methodology, we further optimized the medium for improved FK506 production by CZ-19 in shake flask culture. The optimal medium for enhanced FK506 production was as follows: 17.19 g/L corn starch, 21.78 g/L glucose, 8.06 g/L peptone, and 18.98 mg/L 4-aminobutyric acid. The predicted FK506 titer was 906.49 mg/L, and the experimental data confirmed the validity of the model. The present study demonstrates that S. tsukubaensis CZ-19 is a promising strain for industrial production of FK506.

SNPs in the coding region of bovine MGAT2 gene are associated with body weight and weight gain

Lian Qu,Mingjuan Yang,Jinlong Zhu,Junxia Liu,Mijie Li,Liangzhi Zhang,Xianyong Lan,Chuzhao Lei,Chunlei Zhang,Hong Chen 한국유전학회 2011 Genes & Genomics Vol.33 No.3

Monoacylglycerol acyltransferase 2 (MGAT2), as a candidate gene for quantitative traits, relates to dietary fat uptake, lipids synthesis and storage, which plays a major role in the absorption of dietary fat by catalyzing the resynthesis of triacylglycerol in enterocytes. In this study, based on DNA pool sequencing and PCR‐RFLP methods, polymorphisms of the MGAT2 gene were detected in 1145 Chinese indigenous cattle. The results revealed two novel mutations located on exon 1and exon 5 (NM_001099136.1:m.84G>T and 756A>G). Hence, we described the HaeIII forced PCR–RFLP method in exon1 and a MluI PCR–RFLP method in exon5 to detect them. In addition, the associations of these polymorphisms with growth traits were evaluated in Nanyang cattle. The results showed that only HaeIII locus was associated with body weight and average daily gain aged 6 months, and individuals with genotype TT showed significantly higher body weight and average daily gain than those with genotype GG.