<![CDATA[ABSTRACTThis research carried out isolation of ureolytic bacteria taken from soil samples from the mangrove area of Muara Gembong, Citarum River. The aim was to characterize and to test the urease production activity of the ureolytic bacteria. The study was conducted at the BPPT Environmental Laboratory in Building 820 Geostech, Puspiptek Setu, South Tangerang City, Banten Province, from April until September 2019. The results showed that there were ureolytic bacterial isolates from soil samples taken. The productivity of ureolytic bacterial isolates was indicated by the increasing ammonia concentration and the increase of bacterial cell concentration supported by the pH and temperature factors per volume unit of 10 ml. The increase in ammonia concentration of the six isolates’ test media showed significant differences. The highest increase in ammonia concentration was 15.19 ppm produced by isolate K5A and the second highest was 14.10 ppm by isolate K7. Another productivity testing was performed by determining if there was an increase in the concentration of bacterial cells. Based on the analysis of variance, each isolates significantly affected the increase in bacterial cell concentration. The highest increase in bacterial cell concentration by 250.45×106 CFU/ml occurred in isolates K5A, while isolate K7 indicated the second-highest increase in cell concentration by 233.31×106 CFU/ml.Keywords: ureolytic bacteria, productivity, mangrove sediment, Citarum River EstuaryABSTRAK Penelitian ini melakukan isolasi bakteri ureolitik yang diambil dari sampel tanah dari daerah mangrove dari di Muara Gembong, Sungai Citarum. Tujuannya adalah untuk melakukan karakterisasi dan menguji aktivitas produksi urease terhadap isolat bakteri ureolitik yang ditemukan. Penelitian dilakukan di Laboratorium Lingkungan BPPT di Gedung 820 Geostech, Puspiptek Setu, Kota Tangerang Selatan, Provinsi Banten mulai bulan April sampai dengan September 2019. Enam isolat bakteri dapat diperoleh dari sampel tanah yang diambil. Produktivitas isolat bakteri ureolitik pada penelitian ini dapat ditandai dengan kenaikan konsentrasi amonia kenaikan konsentrasi sel bakteri yang didukung dengan faktor pH dan suhu per satuan volume 10 ml. Kenaikan konsentrasi amonia dari keenam media uji isolat menunjukkan perbedaan yang nyata. Produksi konsentrasi amonia tertinggi sebesar 15,19 ppm dihasilkan oleh isolat K5A dan tertinggi kedua sebesar 14,10 ppm oleh isolat K7. Untuk uji produktivitas juga dilakukan dengan melihat adanya kenaikan konsentrasi sel bakteri. Berdasarkan analisis variansi, masing-masing isolat berpengaruh nyata terhadap kenaikan konsentrasi sel bakteri. Kenaikan konsentrasi sel bakteri tertinggi sebesar 250,45×106  CFU/ml terjadi pada isolat bakteri K5A sedangkan isolat K7 menunjukkan kenaikan konsentrasi sel tertinggi kedua sebesar 233,31×106  CFU/ml.Kata kunci: bakteri ureolitik, produktivitas, sedimen mangrove, Muara Sungai Citarum]]>
