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 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 maintaining sporulation genes was deleted. Meanwhil the sigma-H, which its 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 Bacillus sacPA operon. For the first time, an asporogenic strain of B. cereus was generated that produced higher keratinase (390 U in compare to the 198 U of wild strain) and protease (450 U in compare to the 290 U of wild 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 of poultry industry.