<![CDATA[The development of biofertilizers based on indigenous microorganisms is an important strategy to sustainably enhance crop productivity. Mangrove ecosystems represent potential sources of bacteria with diverse metabolic capabilities, including phosphate-solubilizing bacteria (PSB). However, information regarding the multifunctional characteristics of PSB isolated from the Bengkalis mangrove ecosystem, Riau, Indonesia remains limited. This study aimed to evaluate the potential of 25 PSB from the Bengkalis mangrove ecosystem as biofertilizer candidates by assessing their cellulolytic activity, potassium-solubilizing ability, indole-3-acetic acid (IAA) production, nitrogen-fixing ability, plant safety test, and plant growth-promoting effects on maize (Zea mays L.). The results showed that 12 isolates exhibited cellulolytic activity, 10 isolates were capable of solubilizing potassium, 14 isolates showed nitrogen-fixing ability, and all isolates produced IAA at varying concentrations. Based on a scoring approach integrating multiple plant growth promoting traits, isolate SMK 2.1 showed the highest potential, followed by MA 2.3, SMB 2.1, and RA 1.2 as promising isolates. In the maize growth assay at 7 days after planting, isolate SMK 2.1 was identified as the most promising isolate, producing the highest fresh weight (0.94 ± 0.21 g), root length (7.72 ± 3.21 cm), and shoot length (19.50 ± 5.27 cm) among all treatments. In addition, all isolates showed negative results in the plant safety test. Although the evaluation was limited to the early growth stage, these findings demonstrate that PSB isolated from the Bengkalis mangrove ecosystem have considerable potential as biofertilizer candidates and represent valuable indigenous microbial resources for sustainable agriculture. Key words: Biofertilizer, indole-3-acetic acid, mangrove ecosystem, phosphate-solubilizing bacteria, plant growth-promoting bacteria ABSTRAK Pengembangan biofertilizer berbasis mikroorganisme lokal merupakan strategi penting untuk meningkatkan produktivitas tanaman secara berkelanjutan. Ekosistem mangrove berpotensi menjadi sumber bakteri dengan kemampuan beragam, termasuk bakteri pelarut fosfat (BPF). Namun, informasi mengenai karakter multifungsi BPF asal mangrove di Bengkalis, Riau masih terbatas. Penelitian ini bertujuan untuk mengevaluasi potensi 25 isolat BPF asal ekosistem mangrove Bengkalis sebagai kandidat agen biofertilizer melalui pengujian aktivitas selulolitik, pelarutan kalium, produksi hormon indole-3-acetic acid (IAA), kemampuan penambatan nitrogen, uji keamanan tanaman, serta potensinya dalam memacu pertumbuhan tanaman jagung (Zea mays L.). Hasil penelitian menunjukkan bahwa 12 isolat memiliki aktivitas selulolitik, 10 isolat mampu melarutkan kalium, 14 isolat mampu menambat nitrogen, dan seluruh isolat mampu menghasilkan hormon IAA dengan konsentrasi yang bervariasi. Berdasarkan sistem skoring yang mengintegrasikan berbagai karakter pemacu pertumbuhan tanaman, isolat SMK 2.1 memperoleh nilai tertinggi, diikuti isolat MA 2.3, SMB 2.1, dan RA 1.2 sebagai isolat potensial. Pada uji pemacuan pertumbuhan tanaman jagung umur 7 hari setelah tanam, isolat SMK 2.1 merupakan isolat paling potensial yang ditunjukkan oleh berat segar (0,94±0,21 g), panjang akar (7,72±3,21 cm), dan panjang tajuk (19,5±5,27 cm) yang lebih tinggi dibandingkan perlakuan lainnya. Seluruh isolat juga menunjukkan hasil negatif pada uji keamanan tanaman. Meskipun pengujian masih terbatas pada fase awal pertumbuhan, hasil ini menunjukkan bahwa BPF asal mangrove Bengkalis berpotensi sebagai kandidat biofertilizer dan sumber agen hayati lokal untuk pertanian berkelanjutan. Kata kunci: Biofertilizer, bakteri pelarut fosfat, ekosistem mangrove, indole-3-acetic acid, plant growth-promoting bacteria]]>
