Improvement of multiple-stress tolerance and lactic acid production in lactococcus lactis NZ9000 under conditions of thermal stress by heterologous expression of escherichia coli dnaK

Abdullah-Al-Mahin, Shinya Sugimoto, Chihana Higashi, Shunsuke Matsumoto, Kenji Sonomoto

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

The effects of nisin-induced dnaK expression in Lactococcus lactis were examined, and this expression was shown to improve stress tolerance and lactic acid fermentation efficiency. Using a nisin-inducible expression system, DnaK proteins from L. lactis (DnaKLla) and Escherichia coli (DnaK Eco) were produced in L. lactis NZ9000. In comparison to a strain harboring the empty vector pNZ8048 (designated NZ-Vector) and one expressing dnaKLla (designated NZ-LDnaK), the dnaKEco-expressing strain, named NZ-EDnaK, exhibited more tolerance to heat stress at 40°C in GM17 liquid medium. The cell viability of NZ-Vector was reduced 4.6-fold after 6 h of heat treatment. However, NZ-EDnaK showed 13.5-fold increased viability under these conditions, with a very low concentration of DnaKEco production. Although the heterologous expression of dnaKEco did not effect DnaKLla production, heat treatment Increased the DnaK Lla level 3.5- and 3.6-fold in NZ-Vector and NZ-EDnaK, respectively. Moreover, NZ-EDnaK showed tolerance to multiple stresses, including 3% NaCl, 5% ethanol, and 0.5% lactic acid (pH 5.47). In CMG medium, the lactate yield and the maximum lactate productivity of NZ-EDnaK were higher than the corresponding values for NZ-Vector at 30°C. Interestingly, at 40°C, these values of NZ-EDnaK were not significantly different from the corresponding values for the control strain at 30°C. Lactate dehydrogenase (LDH) activity was also found to be stable at 40°C in the presence of DnaKEco ·These findings suggest that the heterologous expression of dnaKEco enhances the quality control of proteins and enzymes, resulting in improved growth and lactic acid fermentation at high temperature.

Original languageEnglish
Pages (from-to)4277-4285
Number of pages9
JournalApplied and environmental microbiology
Volume76
Issue number13
DOIs
Publication statusPublished - Jul 2010

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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