Engineering of quorum-sensing systems for improved production of alkaline protease by Bacillus subtilis


  • Present address: Harold Tjalsma, Department of Clinical Chemistry/564, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, the Netherlands

Sierd Bron, Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, PO Box 14, 9750 AA Haren, the Netherlands (e-mail:


Aim:  Engineering of Rap-Phr quorum-sensing systems of Bacillus subtilis and subsequent evaluation of the transcription of the aprE gene, encoding a major extracellular alkaline protease.

Methods and Results:  Addition of synthetic Phr pentapeptides to the growth medium, or overproduction of pre-Phr peptides, slightly improved the transcription of the aprE gene in B. subtilis. Disruption of certain rap genes similarly improved the transcription of the aprE gene. The production of extracellular proteolytic enzymes was increased when the rapA mutation was combined with a degU32 (Hy) mutation for hyper-secretion.

Conclusions:  Certain Rap-Phr systems of B. subtilis seem to suppress extracellular AprE production. Although this may be an important feature under natural conditions, repression of AprE production by these systems is not desirable under fermentation conditions.

Significance and Impact of the Study:  Although the levels of aprE transcriptional increase in this study are moderate, engineering of Rap-Phr systems may be used to improve the yield of Bacillus strains that are used for the production of the extracellular protease AprE, or Bacillus strains that use of the aprE promoter for the production of a heterologous protein.