Journal of Industrial Microbiology

, Volume 11, Issue 1, pp 23–28

Enhanced production ofd(−)-lactic acid by mutants ofLactobacillus delbrueckii ATCC 9649

  • Ali Demirci
  • Anthony L. PomettoIII

DOI: 10.1007/BF01583728

Cite this article as:
Demirci, A. & Pometto, A.L. Journal of Industrial Microbiology (1992) 11: 23. doi:10.1007/BF01583728


Chemical mutagenesis with ethyl methanesulfonate (EMS) was used to develop strains ofLactobacillus delbrueckii (ATCC 9649) that tolerated increased lactic acid concentrations while continuously producing the acid. Three mutants (DP2, DP3 and DP4) were compared with wild-typeL. delbrueckii by standing fermentations with different glucose concentrations. All three mutants produced higher levels of lactic acid than the wild-type. In pH-controlled (pH 6.0) stirred-tank-batch fermentations, mutant DP3 in 12% glucose, 1% yeast extract/mineral salt/oleic acid medium produced lactic acid at a rate that was more than 2-times faster than the wild-type. Mutant DP3 also produced 77 g/l lactic acid compared with 58 g/l for the wild-type. Overall, compated with wild-type, the mutants DP2 and DP3 exhibited faster specific growth rates, shorter lag phases, greater lactic acid yields, tolerated higher lactic acid concentrations, and produced as much as 12% lactic acid in 12% glucose, 3% yeast extract/mineral salt/oleic acid medium which required an additional 9% glucose when the residual glucose concentration decreased to ≤3%. Mutant DP3 was stable for over 1.5 years (stored freeze dried). The strain development procedure was very successful; mutants with enhanced lactic acid-producing capacity were obtained each time the procedure was employed.

Key words

Bacterium Lactic acid Lactobacillus delbrueckii Mutagenesis Fermentation 

Copyright information

© Society for Industrial Microbiology 1992

Authors and Affiliations

  • Ali Demirci
    • 1
  • Anthony L. PomettoIII
    • 1
  1. 1.Department of Food Science and Human Nutrition, Center for Crops Utilization ResearchIowa State UniversityAmesUSA

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