Development of an asporogenic Bacillus cereus strain to improve keratinase production in exponential phase by switching sigmaH on and sigmaF off

Abstract

Many bacteria, including the genus Bacillus, are able to produce proteases (keratinase). In Bacillus, proteases are produced in the stationary phase and initial stages of sporulation. Protease production is coordinated with sporulation in which expression of various genes by different sigma factors manages the transition from the exponential to the stationary phase. In the present study the sigma-F gene of an indigenous Bacillus cereus strain, which is involved in transcription of genes maintaining sporulation, was deleted. The sigma-H gene, whose product activates the genes that function in the zero phase of sporulation and inhibits suppression of protease production, and spo0B genes were expressed in the exponential phase under the control of a sucrose-inducible promoter from the Bacillus sacPA operon. For the first time, an asporogenic strain of B. cereus was generated that produced higher keratinase (390 U compared with the 198 U of the wild-type strain) and protease (450 U compared with the 290 U of the wild-type strain) activities in the exponential growth phase by induction with sucrose. The new strain is promising for production of keratinase for degradation of feather waste to produce feather meal for poultry feed and decrease environmental pollution from the poultry industry.