Strain improvement and metabolic flux analysis in the wild-type and a mutantLactobacillus lactis strain forL(+)-lactic acid production

ABSTRACT Expression of d-(−)-lactate dehydrogenase (d-LDH) and l-(+)-LDH genes (ldhDand ldhL, respectively) and production ofd-(−)- and l-(+)-lactic acid were studied inLactobacillus helveticus CNRZ32. In order to develop a host for production of pure l-(+)-isomer of lactic acid, twoldhD-negative L. helveticus CNRZ32 strains were constructed using gene replacement. One of the strains was constructed by deleting the promoter region of the ldhD gene, and the other was constructed by replacing the structural gene ofldhD with an additional copy of the structural gene (ldhL) of l-LDH of the same species. The resulting strains were designated GRL86 and GRL89, respectively. In strain GRL89, the second copy of the ldhL structural gene was expressed under the ldhD promoter. The twod-LDH-negative strains produced onlyl-(+)-lactic acid in an amount equal to the total lactate produced by the wild type. The maximum l-LDH activity was found to be 53 and 93% higher in GRL86 and GRL89, respectively, than in the wild-type strain. Furthermore, process variables forl-(+)-lactic acid production by GRL89 were optimized using statistical experimental design and response surface methodology. The temperature and pH optima were 41Ã¯Â¿Â½C and pH 5.9. At low pH, when the growth and lactic acid production are uncoupled, strain GRL89 produced approximately 20% more lactic acid than GRL86.

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Strain improvement of Rhizopus oryzae for over-production of l(+)-lactic acid and metabolic flux analysis of mutants

Biochemical Engineering Journal ◽

10.1016/s1369-703x(03)00126-8 ◽

2004 ◽

Vol 18 (1) ◽

pp. 41-48 ◽

Cited By ~ 58

Author(s):

Dong-Mei Bai ◽

Xue-Ming Zhao ◽

Xin-Gang Li ◽

Shi-Min Xu

Keyword(s):

Lactic Acid ◽

Metabolic Flux Analysis ◽

Metabolic Flux ◽

Rhizopus Oryzae ◽

Strain Improvement ◽

Flux Analysis

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Study on Temperature Regulation of Lactic Acid Bacteria Using Metabolic Flux Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.356-360.127 ◽

2011 ◽

Vol 356-360 ◽

pp. 127-132

Author(s):

Xiao Jing Xiong ◽

Yong Feng Li

Keyword(s):

Lactic Acid ◽

Quantitative Analysis ◽

Lactic Acid Bacteria ◽

Metabolic Flux Analysis ◽

Metabolic Flux ◽

Lactic Acid Production ◽

Flux Analysis ◽

Culture Temperature ◽

Metabolic Intermediates ◽

Fermentation Stage

Fermentation studies of lactic acid bacteria Rennanqilyf13 were performed to evaluate the potential impacts of culture temperature on cell growth and the production of L-Lactic acid. Quantitative analysis of several metabolic intermediates using metabolic flux analysis (MFA) revealed fluxes during the L-Lactic acid production from glucose. According to the metabolic flux from glucose to L-lactic acid, using different temperature at different fermentation stage maximized the concentration, yield and productivity of L-lactic acid.

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