Development of two methods for rapid screening of recombinant Pichia pastoris strains with high-level expression of β-mannanase

The yeast Pichia pastoris (P. pastoris) has been used for the expression of heterologous proteins with the significant success. However, it is time-consuming to screen the high expression level of the recombinant P. pastoris directly. Thus, for β-mannanase production, developing the accurate, rapid and inexpensive screening method to substitute random screening is certainly required. A simple method based on the size of hydrolysis hole was described here, but this method was not very accurate that could only be used in preliminary screening. To further improve the accuracy, a micro-plate screening method is established, which appears to be more accurate and effective. The efficiency of this screening method is about 10 times higher than that of the general screening strategy of cultivation in shaking flasks. Two methods presented here can also be used for screening of recombinant Pichia strains with high-level expression of other heterologous protein after modification.