The present invention concerns a metabolically engineered microorganism for glycine bioproduction or a salt or an ester thereof, the genome of said microorganism comprises an attenuation of the expression of genes encoding enzymes having glycine cleavage system activity as defined by E.C. 1.4.1.27 together with an overexpressing of threonine dehydrogenase dependent pathway as defined by EC E.C. 1.1.1.103 and E.C. 2.3.1.29 and/or with a threonine aldolase dependent pathway as defined by E.C. 4.1.2.48 or EC 4.1.2.42 or any of its catalytically active variants, its use for the production of glycine or one of its salts or esters. The present invention also concerns a fermentation process using said metabolically engineered microorganism for the production of glycine or one of its salts or esters.