b-Carotene–Producing Bacteria Residing in the Intestine Provide Vitamin A to Mouse Tissues

Vitamin A deficiency (VAD) is an overwhelming public health problem that affects hundreds of millions of people worldwide. A definitive solution to VAD has yet to be identified. Because it is an essential nutrient, vitamin A or its carotenoid precursor b-carotene can only be obtained from food or supplements. In this study, wewanted to establish whether b-carotene produced in themouse intestine by bacteria synthesizing the provitaminA carotenoid could be delivered to various tissueswithin the body. To achieve this, we took advantage of the Escherichia coli MG1655*, an intestine-adapted spontaneous mutant of E. coli MG1655, and the plasmid pAC-BETA, containing the genes coding for the 4 key enzymes of the b-carotene biosynthetic pathway (geranylgeranyl pyrophosphate synthase, phytoene synthase, phytoene desaturase, and lycopene cyclase) from Erwinia herbicola.We engineered the E. coliMG1655* to produce b-carotene during transformationwith pAC-BETA (MG1655*bC) and gavaged wild-type and knockout mice for the enzyme b-carotene 15,15#-oxygenase with this recombinant strain. Various regimens of bacteria administration were tested (single vs. multiple and low vs. high doses). b-Carotene concentration was measured by HPLC in mouse serum, liver, intestine, and feces. Enumeration of MG1655*-bC cells in the feces was performed to assess efficiency of intestinal colonization.We demonstrated in vivo that probiotic bacteria could be used to deliver vitamin A to the tissues of amammalian host. These results have the potential to pave the road for future investigations aimed at identifying alternative, novel approaches to treat VAD. J. Nutr. 144: 608–613, 2014.