title: Construction of a dextran-free Leuconostoc citreum mutant by targeted disruption of the dextransucrase gene.
abstract: OBJECTIVE
  Leuconostoc citreum is an important lactic acid bacterium in fermented foods, but dextran production often causes undesired ropiness. To prevent this side effect, a dextran-free mutant needs to be created.
  
  
  RESULTS
  Homologous recombination of the dextransucrase gene (dsrC) was conducted using a segregationally unstable plasmid, pCBM32-DSUDs. A mutant was obtained on sucrose agar medium, and a site-specific insertional inactivation in the gene was confirmed. When cultured in sucrose medium, the mutant strain produced no dextransucrase or dextran. Additionally, it showed a longer lag phase (9 h) than the wild-type strain (3 h), providing new insights into the role of dextransucrase in carbohydrate metabolism of Leuconostoc.
  
  
  CONCLUSIONS
  In this study, a dextransucrase knockout mutant was constructed. It was found that Leuc. citreum dextransucrase not only synthesizes dextran for cell protection but also provides fructose as an important carbon source for cell growth.
  
  
  CONCLUSIONS
  This knockout mutation was generated for the first time in Leuc. citreum. The dextran-free mutant has the potential to be used for various industrial purposes, including as a starter culture for production of nonviscous fermented foods and as a dextran-free host for production of recombinant proteins.
authors: Department of Food Science, Yanbian University, Yanji, Jilin, China.
authors: Q
authors: Q
authors: Jin
authors: L
authors: L
authors: Li
authors: Y J
authors: YJ
authors: Kim
authors: N S
authors: NS
authors: Han
mesh_terms: D001709:Biotechnology; D050260:Carbohydrate Metabolism; D003911:Dextrans / Q000378:metabolism; D005516:Food Microbiology; D005632:Fructose / Q000378:metabolism; D055786:Gene Knockout Techniques; D005964:Glucosyltransferases / Q000235:genetics*; D007934:Leuconostoc / Q000235:genetics* / Q000254:growth & development; D013395:Sucrose / Q000378:metabolism
chemical_list: D003911:Dextrans; D005632:Fructose; D013395:Sucrose; D005964:Glucosyltransferases; C020025:dextransucrase
keywords: chromosomal gene inactivation; dextran; fermented foods; genetic; lactic acid bacteria