Electronic Theses and Dissertation

Nova Elsa Jwita. (2026). Uji Potensi Biosurfaktan dari Isolat Bakteri Tanah Gua Ek Leuntie, Aceh Besar. [Skripsi, Universitas Syiah Kuala]. Dibawah bimbingan Dr. Rahmad Rizki Fazli, S.Pd., M,Si., dan Dra. Erlidawati, M.Si.

Gua Ek Leuntie di Lhoong, Aceh Besar, merupakan ekosistem bawah tanah unik kaya guano kelelawar dan menyimpan bukti sedimentasi tsunami purba. Kondisi oligotrofik di dalam Gua memicu mikroorganisme indigenus beradaptasi menghasilkan metabolit sekunder berupa biosurfaktan, senyawa ramah lingkungan berpotensi menggantikan surfaktan sintetik. Penelitian campuran (mixed methods) pada Januari–Juni 2026 ini bertujuan mengeksplorasi, mengisolasi, dan mengkarakterisasi morfologi serta biokimia bakteri tanah Gua Ek Leuntie, sekaligus menguji potensinya menghasilkan biosurfaktan. Sampel tanah diambil berdasarkan zonasi (Tanah Kuning, Tanah Hitam, Pasir) dengan pH lingkungan agak asam hingga mendekati netral (5,8–6,4). Tahapan metode meliputi isolasi (pour plate, spread plate, streak plate), pengamatan morfologi makroskopis dan mikroskopis (pewarnaan Gram), uji biokimia urease, pemetaan kurva pertumbuhan (〖"OD" 〗_600" nm" ), serta uji potensi biosurfaktan menggunakan Oil Spreading Test (OST). Eksplorasi ini berhasil mengisolasi tiga jenis bakteri dominan, yaitu: isolat tanah kuning (Pseudomonas sp., Gram-negatif, basil berantai panjang), isolat pasir (Pseudomonas sp., Gram-negatif, basil berantai pendek), dan isolat tanah hitam (Bacillus sp., Gram-positif, basil berantai pendek). Pada uji biokimia, isolat tanah kuning menunjukkan aktivitas enzim urease paling kuat. Sementara itu, kurva pertumbuhan bakteri menunjukkan fase eksponensial terjadi pada jam ke-3 hingga ke-14 sebelum memasuki fase stasioner. Hasil uji OST membuktikan seluruh isolat positif menghasilkan biosurfaktan, dengan aktivitas terbesar ditunjukkan supernatan kultur Bacillus sp. dari tanah hitam yang menghasilkan diameter sebaran minyak sebesar 4,0 cm, diikuti isolat tanah kuning (3,1 cm), dan pasir (1,5 cm). Berdasarkan hasil tersebut, disimpulkan bahwa bakteri indigenus tanah Gua Ek Leuntie, khususnya genus Bacillus sp. dari sampel tanah hitam, memiliki potensi kuat untuk dikembangkan dalam bidang bioteknologi aplikatif.

Kata Kunci: Biosurfaktan, Gua Ek Leuntie, Bacillus sp., Pseudomonas sp., Oil Spreading Test.

Nova Elsa Jwita. (2026). Potential Test of Biosurfactants from Soil Bacterial Isolates of Ek Leuntie Cave, Aceh Besar. [Undergraduate thesis, Universitas Syiah Kuala]. Under the supervision of Dr. Rahmad Rizki Fazli, S.Pd., M.Si., and Dra. Erlidawati, M.Si. Ek Leuntie Cave in Lhoong, Aceh Besar, is a unique underground ecosystem rich in bat guano and preserves evidence of ancient tsunami sedimentation. Oligotrophic conditions inside the cave trigger indigenous microorganisms to adapt by producing secondary metabolites in the form of biosurfactants, eco-friendly compounds potential to replace synthetic surfactants. This mixed-methods research conducted from January to June 2026 aimed to explore, isolate, and characterize the morphology and biochemistry of Ek Leuntie Cave soil bacteria, while testing their potential in producing biosurfactants. Soil samples were collected based on zonation (Yellow Soil, Black Soil, Sand) with slightly acidic to near-neutral pH (5.8–6.4). Methodological stages included isolation (pour plate, spread plate, streak plate), macroscopic and microscopic morphological observation (Gram staining), biochemical urease test, growth curve mapping (〖"OD" 〗_600" nm" ), and biosurfactant potential testing using the Oil Spreading Test (OST). This exploration successfully isolated three dominant bacterial types: yellow soil isolate (Pseudomonas sp., Gram-negative, long-chained bacilli), sand isolate (Pseudomonas sp., Gram-negative, short-chained bacilli), and black soil isolate (Bacillus sp., Gram-positive, short-chained bacilli). In the biochemical test, the yellow soil isolate showed the strongest urease enzyme activity. Meanwhile, the bacterial growth curve indicated that the exponential phase occurred from hours 3 to 14 before entering the stationary phase. The OST results proved that all isolates were positive for producing biosurfactants, with the highest activity shown by the culture supernatant of Bacillus sp. from black soil, producing an oil spreading diameter of 4.0 cm, followed by yellow soil (3.1 cm) and sand (1.5 cm) isolates. Based on these results, it is concluded that the indigenous soil bacteria of Ek Leuntie Cave, particularly the genus Bacillus sp. from the black soil sample, have strong potential for development in applied biotechnology. Keywords: Biosurfactants, Ek Leuntie Cave, Bacillus sp., Pseudomonas sp., Oil Spreading Test.