Optimization of ${\gamma}-Polyglutamic$ Acid Production by Bacillus subtilis ZJU-7 Using a Surface-response Methodology

Shi, Feng,Xu, Zhinan,Cen, Peilin The Korean Society for Biotechnology and Bioengine 2006 Biotechnology and Bioprocess Engineering Vol.11 No.3

The components of the media used to elicit the biosynthesis of $poly-{\gamma}-glutamic$ acid $({\gamma}-PGA)$ by Bacillus subtilis ZJU-7 were investigated, particularly the carbon and nitrogen sources Of the 7 carbon sources investigated, sucrose induced the highest rate of ${\gamma}-PGA$ productivity; among the nitrogen sources, tryptone had the best effect for ${\gamma}-PGA$ production. A $2^{6-2}$ fractional factorial design was used to screen factors that influence ${\gamma}-PGA$ production significantly, and a central composite design was finally adopted to formulate the optimal medium. ${\gamma}-PGA$ productivity improved approximately 2-fold when the optimal medium was used compared with the original nonoptimized medium, and volumetric productivity reached a maximum of 58.2 g/L after a 24-h cultivation period.

Optimization of γ-Polyglutamic Acid Production by Bacillus subtilis ZJU-7 Using a Surface-response Methodology

Zhinan Xu,Feng Shi,Peilin Cen 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.3

The components of the media used to elicit the biosynthesis of poly-γ-glutamic acid (γ-PGA) by Bacillus subtilis ZJU-7 were investigated, particularly the carbon and nitrogen sources. Of the 7 carbon sources investigated, sucrose induced the highest rate of γ-PGA productivity; among the nitrogen sources, tryptone had the best effect for γ-PGA production. A 26-2 fractional factorial design was used to screen factors that influence γ-PGA production significantly, and a central composite design was finally adopted to formulate the optimal medium. γ-PGA productivity improved approximately 2-fold when the optimal medium was used compared with the original nonoptimized medium, and volumetric productivity reached a maximum of 58.2 g/L after a 24-h cultivation period.

Asymmetric reduction of chloroacetophenones to produce chiral alcohols with microorganisms

Zhimin Ou,Jianping Wu,Lirong Yang,Peilin Cen 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.1

Four strains of yeast with reduction activity of chloroacetophenones were screened, in which Saccharomyces cerevisiae B5 showed best reduction activity and stereoselectivity. High optical purity (R)-2'-chloro-1-phenylethanol can be obtained with Saccharomyces cerevisiae B5 as biocatalyst. The influence of several co-substrates on the enantiometric excess (ee%) and yield of (R)-2'-chloro-1-phenylethanol was evaluated. 5% (v/v) ethanol is optimal cosubstrate for (R)-2'-chloro-1-phenylethanol formation. The optimal bioconversion conditions of 2'-chloroacetophenone catalyzed by Saccharomyces cerevisiae B5 are as follows: pH 8.0, 25 oC and 24 h. The yield and the enantiometric excess of (R)-2'-chloro-1-phenylethanol can both reach more than 99% with 10.75 g/l Saccharomyces cerevisiae B5 (the cell dry weight) and 1 g/l 2'-chloroacetophenone used in the biotransformation.

Efficient Bioreduction of Ethyl 4-chloro-3-oxobutanoate to (S)4-chloro-3-hydrobutanoate by Whole Cells of Candida magnoliae in Water/ n-Butyl Acetate Two-phase System

Xua Zhinan,Fang Limei,Lin Jianping,Jiang Xiaoxia,Liu Ying,Cen Peilin The Korean Society for Biotechnology and Bioengine 2006 Biotechnology and Bioprocess Engineering Vol.11 No.1

The asymmetric biosynthesis of ethyl (S)-4-chloro-3-hydrobutanoate from ethyl 4-chloro-3-oxobutanoate was investigated by using whole cells of Candida magnoliae JX120-3 without the addition of glucose dehydrogenase or $NADP^+/NADPH$. In a one-phase system, the bioconversion yield was seriously affected on the addition of 12.1 g/L ethyl 4-chloro-3-oxobutanoate. In order to reduce this substrate inhibition, a water/ n-butyl acetate two-phase system was developed, and the bioreduction conditions optimized with regard to the yield and product enantiometric excess value. The optimal conditions were as following: water to n-butyl acetate volume ratio of 1:1, 4.0 g DCW/L active cells, 50 g/L glucose and $35^{\circ}C$. By adopting a dropwise substrate feeding strategy, high concentration of ethyl 4-chloro-3-oxobutanoate (60 g/L) could be asymmetrically reduced to ethyl (S)-4-chloro-3-hydrobutanoate with high yield (93.8%) and high enantiometric excess value (92.7%).

Improvement of Pristinamycin Production by Genome Shuffling and Medium Optimization for Streptomyces Pristinaespiralis

Bo Xu,Zhihua Jin,Qingchao Jin,Ninghui Li,Peilin Cen 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.2

To isolate an improved pristinamycin producing strain of Streptomyces pristinaespiralis, the technique of Genome shuffling was used which resulted in a high-yield recombinant G 3-56 strain. Strain G 3-56 yielded 322 ± 17 mg/L of pristinamycin which was 11.4-fold higher than that of the initial strain and 3.7-fold higher than strain UN-78 which previously had the highest yield of pristinamycin. The genetic characteristics of the recombinant G 3-56 strain was stable as revealed by our subculture experiments. The optimal production medium was determined using the orthogonal matrix method. Under the optimal medium conditions, the maximum yield of pristinamycin was 412 mg/L with about 1.24-fold higher than the original medium. To isolate an improved pristinamycin producing strain of Streptomyces pristinaespiralis, the technique of Genome shuffling was used which resulted in a high-yield recombinant G 3-56 strain. Strain G 3-56 yielded 322 ± 17 mg/L of pristinamycin which was 11.4-fold higher than that of the initial strain and 3.7-fold higher than strain UN-78 which previously had the highest yield of pristinamycin. The genetic characteristics of the recombinant G 3-56 strain was stable as revealed by our subculture experiments. The optimal production medium was determined using the orthogonal matrix method. Under the optimal medium conditions, the maximum yield of pristinamycin was 412 mg/L with about 1.24-fold higher than the original medium.

Adsorption behavior of L_tryptophan on ion exchange resin

Wei Luo,Lei Huang,Hao Chen,Limei Fang,Jin Huang,Zhinan Xu,Peilin Cen 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5

A batch method was applied to investigate the adsorption behavior and mechanisms of L_tryptophan (Ltrp)on ion exchange resins. HZ-001 and JK006 were proved to be ideal adsorbents due to their large loading capacity and favorable selective adsorption for L-trp. Langmuir, Freundlich, and Dubinin-Radushkevich equations were applied to simulate the experimental data to describe the adsorption process of L_trp onto HZ_001 and JK006. The maximum loading capacity (at pH 5.0, 30 ℃), determined by the Langmuir and Dubinin-Radushkevich models, was close to each other (833 mg/g vs. 874 mg/g) for HZ_001, while discrepant (833 mg/g vs. 935 mg/g) for JK006. Three diffusion-controlled kinetic models were utilized to analyze the results in order to identify the adsorption mechanism. The adsorption kinetics of L_trp onto cation exchange resins was investigated under different experimental conditions, including initial solution pH, temperature, initial L-trp concentration, and adsorbent dosage. Moreover, the diffusion process of L_trp onto HZ_001 and JK006 was evaluated at different initial adsorbate concentrations. The thermodynamic parameters,obtained from the kinetic data, demonstrated that L-trp could be adsorbed spontaneously onto both resins.

Kinetics and optimization of L-tryptophan separation with ion-exchange chromatography

Wei Luo,Limei Fan,Peilian Wei,Hao Chen,Limei Fang,Jin Huang,Zhinan Xu,Peilin Cen 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.5

Adsorption and desorption of L-tryptophan (L-trp) on strong acid cation exchange resin were investigated in a fixed-bed column. L-trp was effectively adsorbed onto the resin HZ-001, with the loading capacity and breakthrough time determined. Four kinetic models, including Adams-Bohard, Wolborska, Thomas, and Yoon-Nelson models,were adopted to determine the kinetic parameters of adsorption and to predict the breakthrough curves. The results showed that the models used described the breakthrough well. Desorption of L-trp from the column bed was performed using aqueous ammonia as the eluant. Optimum procedure was obtained with 2.0M aqueous ammonia at the elution velocity of 6 BV/h. Five cycles of adsorption-elution-regeneration were conducted to evaluate the column reutilization.