Overexpression of a heterologous protein,haloalkane dehalogenase,in a poly-beta-hydroxybutyrate-deficient strain of the facultative methylotroph Methylobacterium extorquens AM1

Using an expression vector containing p(mxaF'), a strong native promoter, expression of a model heterologous protein, haloalkane dehalogenase, from Xanthobacter autotrophicus GJ10 was achieved in the methylotrophic bacterium, Methylobacterium extorquens AM1. Although expression using the wild-type strain was <5% of total cell protein, expression at a level of 10% of the total cell protein was achieved in a mutant unable to synthesize poly-beta-hydroxybutyrate granules. Two other tested heterologous proteins, catechol dioxygenase and green fluorescent protein, were expressed at moderate levels in both wild-type and the PHB-negative strain. These results suggest that the M. extorquens PHB-negative strain is a possible platform for overexpression of heterologous proteins with labeled or unlabeled methanol as a starting material.