A new poly(3-hydroxypropionate) (P3HP) biosynthetic pathway employing beta-alanine as an intermediate from an inexpensive carbon source was developed in recombinant Escherichia coli. After a series of systematic optimization, the genes for (L)-aspartate decarboxylase and its maturation factor (panD and panM, from E. coli), beta-alanine-pyruvate transaminase (pp0596, from Pseudomonas putida), 3-hydroxy acid dehydrogenase and 3-hydroxypropionyl-CoA synthase (ydfG and prpE respectively, from E. coli), and polyhydroxyalkanoate synthase (phaC1, from Cupriavidus necator) were cloned and expressed in E. coli. Under shake-flask conditions, the recombinant strain produced 0.5 g P3HP l(-1) from glycerol and glucose, up to 10.2 % of CDW. Though the content of P3HP was low, this pathway has some advantages over other reported pathways, such as being redox neutral, does not require any coenzyme, and can use a wide range of carbon sources.