Effect of Phytate-Degrading Probiotics on Broiler Performance
Askelson, Tyler E
MetadataShow full item record
Probiotics have been demonstrated to promote growth, stimulate immune responses, and improve the microbial 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. Phytases isolated from microorganisms are increasingly supplemented in feed to improve digestibility and reduce anti-nutritive effects of phytate. The microbial origin of these enzymes suggests a potentially important mechanism of probiotic functionality. Our objective was to investigate 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 an approximately 44 kDa protein in the culture supernatants of Lactobacillus pTD003 transformants corresponding to the predicted molecular weight of B. subtilis phytase. The phytate degrading ability of these cultures was evaluated by determining the amount of inorganic phosphate released from sodium phytate. 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. The effect of administration of recombinant phytase-expressing L. gallinarum and L. gasseri was evaluated in broiler chicks fed a phosphorous deficient diet (0.25% aP). Phytase-expressing L. gasseri improved weight gain (P < 0.05) of broiler chickens to a level comparable to chickens fed a phosphorous adequate control diet (0.40% aP) demonstrating proof of-principle that administration of phytate-degrading probiotic cultures can improve performance of livestock animals. Additionally, this will inform future studies investigating whether probiotic cultures are able to combine the performance benefits of feed enzymes with the animal health and food safety benefits traditionally associated with probiotics.