Born in Constantinople, he was educated at the theological school in Chalce, and at the universities of Leipzig, Munich, and Berlin. He became a professor at Chalce in 1861. In 1867 he went to head the Patriarchal School in Constantinople, leaving in 1875 to attend the Old Catholic conference in Bonn, during which he was appointed metropolitan of Serrae in Macedonia. In 1877 he transferred to Nicomedia.
In 1877, he participated in a commission dealing with plundered monasteries in Moldavia and Wallachia.
In 1873PhilotheosBryennios, then Head Master of the higher Greek school at Constantinople, but now Metropolitan of Nicomedia, discovered a remarkable collection of manuscripts in the library of the Jerusalem Monastery of the Most Holy Sepulchre at Constantinople.
In 1875Bryennios, who had been chosen Metropolitan of Serrae during his absence at the Old Catholic conference in Bonn, published at Constantinople the two Epistles of Clement, with prolegomena and notes; giving the text found in the Jerusalem Codex, as he termed it.
Bryennios and Harnack assign, as the date, between 120 and 160; Hilgenfeld, 160 and 190; English and American scholars vary between A.D. 80 and 120.
It is the only rediscovered Christian text during the last 150 years of discoveries in libraries or in papyri to receive wide acceptance by the Catholic and Orthodox Churches.
Considered lost, the Didache was rediscovered in 1883 by PhilotheosBryennios, a Greek Orthodoxmetropolitan bishop of Nicomedia, in the Greek Codex Hierosolymitanus written in 1053, from which he had already published the full text of the Epistles of Clement in 1875.
Shortly after Bryennios' initial publication, the scholar Otto von Gebhardt identified a Latin manuscript in the Abbey of Melk in Austria as containing a translation of the first part of the Didache; later scholars now believe that to be an independent witness to the tradition of the Two Ways section (see below).