Probiotics have been demonstrated to promote growth, stimulate immune responses, and improve food safety of poultry. While widely used, their effectiveness is mixed, and the mechanisms through which they contribute to poultry production are not well understood. Microbial phytases are increasingly supplemented in feed to improve digestibility and reduce antinutritive effects of
phytate. The microbial origin of these exogenous
enzymes suggests a potentially important mechanism of probiotic functionality. We investigated
phytate degradation as a novel probiotic mechanism using recombinant Lactobacillus cultures expressing Bacillus subtilis
phytase. B. subtilis phyA was
codon optimized for expression in Lactobacillus and cloned into the expression vector pTRK882. The resulting plasmid, pTD003, was transformed into Lactobacillus acidophilus, Lactobacillus gallinarum, and Lactobacillus gasseri. SDS-PAGE revealed a
protein in the culture supernatants of Lactobacillus pTD003 transformants with a molecular weight similar to that of the B. subtilis
phytase. Expression of B. subtilis
phytase increased
phytate degradation of L. acidophilus, L. gasseri, and L. gallinarum approximately 4-, 10-, and 18-fold over the background activity of empty-vector transformants, respectively.
Phytase-expressing L. gallinarum and L. gasseri were administered to broiler chicks fed a
phosphorus-deficient diet.
Phytase-expressing L. gasseri improved
weight gain of broiler chickens to a level comparable to that for chickens fed a control diet adequate in
phosphorus, demonstrating proof of principle that administration of
phytate-degrading probiotic cultures can improve performance of livestock animals. This will inform future studies investigating whether probiotic cultures are able to provide both the performance benefits of feed
enzymes and the animal health and food safety benefits traditionally associated with probiotics.