Abstract
The genes
gdh
and
pqqABCDE
encoding glucose dehydrogenase and its pyrroloquinoline quinone cofactor were cloned from the mineral phosphate-solubilizing (MPS) bacterium
Serratia marcescens
CTM 50650. We investigated, for the first time, the impact of their coexpression in
Escherichia coli
on MPS ability. The production of recombinant PQQGDH conferred high MPS activity to the engineered
E
.
coli
. In fact, the amounts of soluble phosphorus (P) produced from tricalcium phosphate, hydroxyapatite, and Gafsa rock phosphate (GRP) were 574, 426, and 217 mg/L, respectively. In an attempt to increase the soluble P concentration, the
E
.
coli
strain coexpressing the
gdh
and
pqqABCDE
genes was immobilized in agar, calcium alginate, and k-carrageenan and was then further applied in a repeated batch (six batches) fermentation process to solubilize GRP. Compared to other encapsulated systems, alginate cell beads were noted to yield the highest concentration of soluble P, which attained 300 mg/L/batch. MPS efficiency was maximal in the presence of 5 and 40 g/L of GRP and glucose, respectively.