-239- ABSTRACT Borobudur Temple is a historical heritage building located in an open area and made of porous building materials (stone materials). This condition makes the Borobudur Temple susceptible to various problems related to degradation and weathering. Biodeterioration of Borobudur Temple may be caused by activities of living organisms present in the biofilm of stone. Continuous monitoring and evaluation need to be carried out by observing and isolating the growth of micro-organisms, including epilithic microalgae. Therefore, this study aims to isolate and identify epilithic microalgae from the biofilm on Borobudur Temple stones. Epilithic microalgae were isolated to obtain a uni-algae and maintained under culture conditions. The morphological of microalgae were observed using light microscopy, while the 18S rRNA gene sequence determined the molecular identification of microalgae for eukaryotic and 16S rRNA sequence for prokaryotic. A total of nine epilithic microalgae were successfully isolated from the biofilm of Borobudur Temple stones. The isolated were identified as Ankistrodesmus falcatus, Tetraselmis cordiformis, Pseudendoclonium arthropyreniae, Anabaena cylindrica, Nostoc gelatinosum, Oscillatoria limnetica, Messastrum gracile, Stigeoclonium aestivale, and Scenedesmus acuminatus. This is the first study for the identification of microalgae from Borobudur temple stones. The isolates will be collected and will be used as a source for further study. Keywords: 16S rRNA gene, 18S rRNA gene, epilithic algal, molecular identification, phylogeny, subaerial Research Article Epilithic Microalgae Isolated from Biofilm on Borobudur Temple Stone Debora Christin Purbani 1 *, Ade Lia Putri 1 , Moh. Habibi 2 1) Research Center for Biology, Indonesian Institute of Sciences (LIPI) 16911, Bogor, Indonesia. 2) Borobudur Conservation Office, Indonesian Ministry of Education and Culture 56553, Magelang, Indonesia. Submitted: 31 August 2020; Accepted: 17 November 2020; Published: 15 December 2020 Journal of Tropical Biodiversity and Biotechnology Volume 05, Issue 03 (2020): 239 — 246 DOI: 10.22146/jtbb.59216 INTRODUCTION Borobudur Temple is located in Borobudur Village, Borobudur District, Magelang Regency, Central Java Province. This historical heritage temple compound was built in an open area on a modified hill, with a height of 265 meters above sea level, with a length of 121.66 meters, width 121.38 meters, and a height of 34.50 meters. The structure of the Borobudur Temple consists of nine terraces and a main stupa at the top. There are six rectangular terraces and three circular terraces, covering the Kamadhatu, Rupadhatu, and Arupadhatu levels. Borobudur Temple built using the andesite stone material from rivers around the Borobudur Temple with a total of ± 2,000,000 pieces of stones (Banindro, 2015; Salazar, 2018). The restoration of Borobudur Temple has been carried out twice, the Dutch East Indies government carried out the first restoration under the leadership of Van Erp, and the second restoration was carried out by the Indonesian government chaired by Soekmono (Voûte & Voute, 1973; Gunarto, 2007; Banindro, 2015). Rehabilitation of Borobudur Temple has also been done after Mount Merapi's eruption in 2010 to clean up volcanic ash, which is chemically acidic and can damage this historic temple stone. Demolition of stone blocks has been carried out to improve the clogged water and drainage system, which is clogged with volcanic dust mixture mixed with rainwater, followed by reforestation and planting of trees in the surrounding environment to stabilize the temperature (Yulianto et al., 2013; Khoirunnisa, Warsono, & Suryaningsih, 2014). After the Borobudur Temple has been restored and rehabilitated, it does not mean that the temple maintenance has been completed. There is no *Corresponding author Tel.: +6287837107877 Email: deborachristin22@gmail.com © 2020, J. Tropical Biodiversity Biotechnology (CC BY-SA 4.0)