Effect of additives on structure and corrosion resistance of ceramic coatings on Mg–Li alloy by micro-arc oxidation

Shi Lingling,Xu Yongjun,Li Kang,Yao Zhongping,Wu Songquan 한국물리학회 2010 Current Applied Physics Vol.10 No.3

In order to improve the corrosion resistance of ceramic coatings formed on Mg–5mass%Li substrate by micro-arc oxidation (MAO) method, two kinds of additives (Na2B4O7 and EDTA) were doped in Na2SiO3–Na3PO4 solution system. The surface and cross-section morphology feature, phase composition and elemental composition were examined by SEM, XRD and EDX, respectively. Corrosion resistance of ceramic coating was tested by electrochemical methods. It was revealed that all coatings were composed of MgO and Mg2SiO4, and had porous surface structure. Doping of additives had little effect on the elemental composition, while it influenced the morphological feature of the coating. The results of electrochemical tests showed that the coatings prepared in the solutions with additive had good corrosion resistance. The addition of EDTA to the solution made coatings thinner and more uniform which resulted in better general corrosion resistance. The addition of Na2B4O7 to the solution made coatings much thicker and compacter, which improved the pitting corrosion resistance.

Improvement of ATP regeneration efficiency and operation stability in porcine interferon-α production by Pichia pastoris under lower induction temperature

Minjie Gao,Zhongping Shi,Shijuan Dong,Ruisong Yu,Jianrong Wu,Zhiyong Zheng,Xiaobei Zhan 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.6

The performance of traditional heterologous protein production by Pichia pastoris with methanol induction at 30 ℃ is poor, characterized by low ATP regeneration rate and weak operation stability. A low temperature induction strategy at 20 ℃ was thus adopted for efficient porcine interferon-α production in a 10 L fermentor. With the strategy,maximal methanol tolerance level could reach about 40 g/L to effectively deal with methanol concentration variations,so that the complicated on-line methanol measurement system could be eliminated. Moreover, metabolic analysis based on multiple state-variables measurements indicated that pIFN-α antiviral activity enhancement profited from the formation of an efficient ATP regeneration system at 20℃ induction. Compared to the induction strategy at 30 ℃, the proposed strategy increased the ATP regeneration rate by 49-66%, the maximal p_IFN-α antiviral activity was enhanced about 20-fold and reached a higher level of 1.5×10^6 IU/mL.

Evaluation of High Butanol/Acetone Ratios in ABE Fermentations with Cassava by Graph Theory and NADH Regeneration Analysis

Zhigang Li,Zhongping Shi,Xin Li,Le Li,Junping Zheng,Zhenggang Wang 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.4

Higher butanol/acetone ratio is always desirable in ABE fermentation, and this ratio is closely associated with the complicated patterns of metabolic reactions and NADH generation rate. The patterns of acetate/butyrate formation and re-assimilation in multiple closed reaction loops, as well as NADH regeneration in ABE fermentation using different substrates varies. In this study, we evaluated butanol/acetone ratio in ABE fermentations utilizing cassava and corn based media by graph theory and NADH regeneration analysis. The theoretical calculations and experimental data revealed that a lower metabolic strength in butyrate loop and enhanced NADH generation rate were responsible for the achievement of higher butanol/acetone ratio when fermenting cassava based substrate. In traditional fermentations and extractive fermentations with oleyl alcohol/bio-diesel as the extractants when using cassava based substrate, butanol/acetone ratios reached 2.24, 2.84,and 2.19 with the increasing increments of 14.9, 61.4, and 6.8% respectively, while butanol productivities stayed at comparably high levels as compared with those of the fermentations when cultivating on corn based substrate.

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

Effect of Metabolic Structures and EnergyRequirements on Curdlan Production byAlcaligenes faecalis

Xiao Bei Zhan,Zhi-Yong Zheng,Jin Woo Lee,Zhongping Shi,Lei Wang,Li Zhu,Jian-Rong Wu,Chi Chung Lin 한국생물공학회 2007 Biotechnology and Bioprocess Engineering Vol.12 No.4

A comprehensive metabolic network was proposed for Alcaligenes faecalis and employed in a stoichiometrically based flux balance model for curdlan production optimization. The maximal yield of curdlan was evaluated for curdlan batch production. Various metabolic structures and metabolic pathway distributions related with the curdlan maximal yield was evaluated. The results showed that the energy efficiency rather than the substrate supply was the major constraint for the enhancement of curdlan production. The increase in specific rate of glucose uptake could enhance curdlan production yield due to the decrease of the ratio of metabolic maintenance to substrate consumption. However, some of the energy loss and nutrient limitation associated with the increase of metabolic maintenance would adversely affect the conversion efficiency of the substrate.

Simulation of computational fluid dynamics and comparison of cephalosporin C fermentation performance with different impeller combinations

Shengbing Duan,Guoqiang Yuan,Yanli Zhao,Weijia Ni,Hongzhen Luo,Zhongping Shi,Fan Liu 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.5

Cephalosporin C (CPC) fermentation by Acremonium chrysogenum is an extremely high oxygen-consuming process and oxygen transfer rate in a bioreactor directly affects fermentation performance. In this study, fluid dynamics and oxygen transfer in a 7 L bioreactor with different impellers combinations were simulated by computational fluid dynamics (CFD) model. Based on the simulation results, two impeller combinations with higher oxygen transfer rate (KLa) were selected to conduct CPC fermentations, aiming at achieving high CPC concentration and low accumulation of major by-product, deacetoxycephalosporin (DAOC). It was found that an impeller combination with a higher KLa and moderate shear force is the prerequisite for efficient CPC production in a stirred bioreactor. The best impeller combination, which installed a six-bladed turbine and a four-pitched-blade turbine at bottom and upper layers but with a shortened impellers inter-distance, produced the highest CPC concentration of 35.77 g/L and lowest DAOC/CPC ratio of 0.5%.

Enhanced 2,5-Furandicarboxylic Acid (FDCA) Production in Raoultella ornithinolytica BF60 by Manipulation of the Key Genes in FDCA Biosynthesis Pathway

( Haibo Yuan ),( Yanfeng Liu ),( Xueqin Lv ),( Jianghua Li ),( Guocheng Du ),( Zhongping Shi ),( Long Liu ) 한국미생물 · 생명공학회 2018 Journal of microbiology and biotechnology Vol.28 No.12

The compound 2,5-furandicarboxylic acid (FDCA), an important bio-based monomer for the production of various polymers, can be obtained from 5-hydroxymethylfurfural (HMF). However, efficient production of FDCA from HMF via biocatalysis has not been well studied. In this study, we report the identification of key genes that are involved in FDCA synthesis and then the engineering of Raoultella ornithinolytica BF60 for biocatalytic oxidation of HMF to FDCA using its resting cells. Specifically, previously unknown candidate genes, adhP3 and alkR, which were responsible for the reduction of HMF to the undesired product 2,5- bis(hydroxymethyl)furan (HMF alcohol), were identified by transcriptomic analysis. Combinatorial deletion of these two genes resulted in 85.7% reduction in HMF alcohol formation and 23.7% improvement in FDCA production (242.0 mM). Subsequently, an aldehyde dehydrogenase, AldH, which was responsible for the oxidation of the intermediate 5-formyl-2-furoic acid (FFA) to FDCA, was identified and characterized. Finally, FDCA production was further improved by overexpressing AldH, resulting in a 96.2% yield of 264.7 mM FDCA. Importantly, the identification of these key genes not only contributes to our understanding of the FDCA synthesis pathway in R. ornithinolytica BF60 but also allows for improved FDCA production efficiency. Moreover, this work is likely to provide a valuable reference for producing other furanic chemicals.

Effect of Metabolic Structures and Energy Requirements on Curdlan Production by Alcaligenes faecalis

Zheng, Zhi-Yong,Lee, Jin-Woo,Zhan, Xiao Bei,Shi, Zhongping,Wang, Lei,Zhu, Li,Wu, Jian-Rong,Lin, Chi Chung Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.4

A comprehensive metabolic network was proposed for Alcaligenes faecalis and employed in a stoichiometrically based flux balance model for curdlan production optimization. The maximal yield of curdlan was evaluated for curdlan batch production. Various metabolic structures and metabolic pathway distributions related with the curdlan maximal yield was evaluated. The results showed that the energy efficiency rather than the substrate supply was the major constraint for the enhancement of curdlan production. The increase in specific rate of glucose uptake could enhance curdlan production yield due to the decrease of the ratio of metabolic maintenance to substrate consumption. However, some of the energy loss and nutrient limitation associated with the increase of metabolic maintenance would adversely affect the conversion efficiency of the substrate.