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RISS 인기검색어
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- 저자 : Xiaobei Zhan (검색결과 4 건)
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Zhi-Yong Zheng,Xiaobei Zhan,Chi Chung Lin,Shan-Jing Yao 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.1
Tryptone has multiple and complex effects on cell physiology and process performance in pulse fed-batch cultivation of recombinant Escherichia coli. By applying feedback control of dissolved oxygen signal responding to pulse in the feed rate, the production of acetate was avoided and the optimization of production of recombinant human epidermal growth factor (hEGF) was successfully achieved. With the addition of an optimum amount of tryptone along with glucose in the pulse fed-batch cultivation of E. coli, the ability of the cell to divide and the stability of the plasmid within the bacteria were improved. Consequently, segregation of the cells into a viable but non-culturable physiological state was alleviated. Addition of tryptone also enhanced cell respiration before and after hEGF expression and thus further benefited the production of recombinant hEGF. Excessive addition of tryptone resulted in low sensitivity of the oscillation of dissolved oxygen signal and poor operability of pulse fed-batch cultivation as this led to an accumulation of acetate, which weakened the dissolved oxygen signal responses. Consequently, the production of recombinant protein was considerably reduced. By combining the process performance and the positive effect of complex media pulse addition on bacterial metabolism, the optimal production conditions of hEGF were successfully determined. A high cell density of 91 g/L dry cell weight was obtained under these optimal production conditions. Furthermore, a high level of 0.24 g/L hEGF was attained leading to a 32.6% increase in product yield as compared to the controls.
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Enhanced Curdlan Production in Agrobacterium sp. ATCC 31749 by Addition of Low-polyphosphates
Lijun Yu,Jianrong Wu,Jia Liu,Xiaobei Zhan,Zhiyong Zheng,Chi Chung Lin 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1
A large amount of adenosine triphosphate with high energy phosphate bonds is required for uridine triphosphate regeneration during curdlan biosynthesis by Agrobacterium sp. ATCC 31749. To supply high energy for curdlan synthesis, three low-polyphosphates (Na_4P_2O_7,Na_5P_3O_10, and (NaPO_3)_6) with higher energy phosphate bonds were employed to substitute for KH_2PO_4-K_2HPO_4in fermentation medium. Two genes encoding the polyphosphate metabolizing enzymes, polyphosphate kinase and exopolyphosphatase, were amplified and showed 95%homology to those in Agrobacterium sp. C58 by sequence analysis. The curdlan yields were enhanced by 23 and 134% when phosphate concentrations 0.024 mol/L of Na_5P_3O_10 and 0.048 mol/L of (NaPO_3)_6 respectively, were added in the medium. The maximum curdlan yield of 30 ±1.02 g/L was obtained with the addition of 0.048 mol/L of (NaPO_3)_6 with 5 g/L CaCO_3 in the medium. When CaCO_3 was removed from the culture and the three lowpolyphosphates were added, the pH and biomass yield dropped remarkably and little or no curdlan was produced. The culture containing 0.048 mol/L of (NaPO_3)_6 was mixed with KH_2PO_4-K_2HPO_4 and CaCO_3 in the medium,but showed no effect on curdlan production. However,curdlan yield was improved by 49 ~ 60% when CaCO_3was removed from the medium and KH_2PO_4-K_2HPO_4acted as a buffer. It appears that the positive effect of (NaPO_3)_6 on curdlan production required the buffering capacity of CaCO_3 and the absence of KH_2PO_4-K_2HPO_4competing as a phosphate supplier.
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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.
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