Secretion of Biologically Active Heterologous Oxalate Decarboxylase (OxdC) in Lactobacillus plantarum WCFS1 Using Homologous Signal Peptides

Current treatment options for patients with hyperoxaluria and calcium oxalate stone diseases are limited and do not always lead to sufficient reduction in urinary oxalate excretion. Oxalate degrading bacteria have been suggested for degrading intestinal oxalate for the prevention of calcium oxalate stone. Here, we reported a recombinant Lactobacillus plantarum WCFS1 (L. plantarum) secreting heterologous oxalate decarboxylase (OxdC) that may provide possible therapeutic approach by degrading intestinal oxalate. The results showed secretion and functional expression of OxdC protein in L. plantarum driven by signal peptides Lp_0373 and Lp_3050. Supernatant of the recombinant strain containing pLp_0373sOxdC and pLp_3050sOxdC showed OxdC activity of 0.05 U/mg and 0.02 U/mg protein, while the purified OxdC from the supernatant showed specific activity of 18.3 U/mg and 17.5 U/mg protein, respectively. The concentration of OxdC protein in the supernatant was 8-12 μg/mL. The recombinant strain showed up to 50% oxalate reduction in medium containing 10 mM oxalate. In conclusion, the recombinant L. plantarum harboring pLp_0373sOxdC and pLp_3050sOxdC can express and secrete functional OxdC and degrade oxalate up to 50% and 30%, respectively.