Lipopeptides show great potential for biomedical application. Several lipopeptides exhibit narrow and broad-spectrum inhibition activities. The aim of the study is to characterize the lipopeptides produced by B. amyloliquefaciens strain MD4-12 and evaluate the synergistic antimicrobial activity in combination with a conventional antibiotic against Gram-negative bacteria. B. amyloliquefaciens strain MD4-12 was isolated from oil-contaminated soil. The isolate was cultivated in McKeen medium, and the lipopeptides were isolated by precipitation and extraction with methanol. Characterization of the lipopeptides by ESI-MS gave nine mass ion peaks with m/z 994–1072, resulted from protonating of the main ions in [M + H]+ and [M + Na]+ ion form. These mass ion peaks attributed to surfactin homologs. By tandem mass spectrometry, five variants of surfactin with the same amino acid sequence in peptide moiety could be revealed. The peptide moiety contains seven amino acids identified as Glu-Leu/Ile-Leu-Val-Asp-Leu-Leu/Ile while the fatty acid moiety comprises a different length of chain from C12 to C16. Surfactin showed antibacterial activity against various Gram-positive and Gram-negative bacteria. Combination surfactin with ampicillin showed a synergistic effect against P. aeruginosa ATCC 27853.

Biosurfactants are microbial metabolites that work as surface active agents produced by some microorganisms, including bacteria, yeast and fungi. Interests in biosurfactants are growing due to their broad possible applications such as in the pharmaceutical, cosmetic, agricultural and food industries, environmental protection and crude oil drilling (Banat et al. 2010; Meena et al. 2015). Their important characteristics such as biological activities, emulsifying, foaming, soaping and dispersing acquire them for multiple applications. Based on their chemical structures, biosurfactants are divided into five major classes, i.e. lipopeptides, glycolipids, phospholipids, neutral lipids, and polymeric compounds. One of the most important families of lipopeptide class is surfactin. Surfactin is a cyclic molecules consisting of a fatty acid of variable length (hydrophobic moiety) linked to a short Surfactin is a lipopeptide biosurfactant that show potential biomedical application due to its activities such as antiviral, antibacterial, antifungi, anticancer, and antimycoplasma. Bacillus amyloliquefaciens MD4-12, isolated from oil-contaminated soil, produced promising yield of surfactin in McKeen medium. The production of surfactin was influenced by many fermentation process parameters such as carbon, nitrogen, minerals and also environmental conditions such as pH and agitation. Therefore, to obtain high yield of surfactin by B. amyloliquefaciens MD4-12, optimization of process production was conducted in shake flask fermentation using response surface methodology. McKeen medium composition was used as basal medium. Screening of the best carbon and nitrogen source were selected in preliminary experiments followed by selection of the influencing significant parameters on surfactin production using Plackett-Burman design. Selected parameters were optimized by central composite design and for the data analysis was used response surface methodology. The-1 result showed that the optimum medium composition contained (g L) 45.0 glucose, 6.33 urea, 1.0 monosodium glutamate, 1.85 MgSO .7H O, 0.4 KCl, 0.5 K HPO , and 0.5 mL trace elements. The surfactin yield at optimal 4 2 2 4-1 condition was 1.25 g L , increased 2.4 times compared to condition prior to optimization.

ABSTRAK Mikroorganisme penghasil biosurfaktan telah diisolasi dari air laut yang tercemar minyak yang diambil dari beberapa lokasi dermaga di Indonesia. Lima dari 155 isolat yang diisolasi mampu menghasilkan biosurfaktan yang tinggi melalui proses fermentasi menggunakan medium produksi Marine Broth (Difco). Isolat ML4-10 yang diisolasi dari kawasan dermaga kilang minyak Pertamina di Cilacap menunjukkan kemampuan menghasilkan biosurfaktan tertinggi. Pada uji biosurfaktan yang dihasilkan oleh isolat ML4-10 menunjukkan bahwa aktifitas emulsifikasi dan oil displacement, berturut-turut adalah 54,1 ± 0,8 dan 10,5 ± 0,3. Biosurfaktan dari ML4-10 juga menunjukkan nilai positif pada uji oil drop test. Pada uji aktifitas emulsifikasi dan oil displacement menggunakan berbagai sumber minyak, biosurfaktan dari ML4-10 juga menunjukkan aktifitas yang tinggi, hal ini menunjukkan biosurfaktan mempunyai potensi aplikasi yang luas.Kata kunci: biosurfaktan, pencemaran minyak, air laut, mikroorganisme, isolat

Santan merupakan bahan tambahan makanan yang banyak digunakan diberbagai masakan khususnya di Indonesia. Seiring dengan era modern yang menginginkan serba cepat dan praktis maka santan cair dalam kemasan menjadi satu kebutuhan masyarakat. Santan merupakan emulsi minyak dalam air, dimana stabilitas emulsi sangat rendah. Emulsi santan jika disimpan dalam waktu yang singkat akan terpisah menjadi dua bagian, yaitu lapisan serum dan lapisan krim. Guna meningkatkan kestabilan emulsi santan maka salah satu upaya adalah dengan menambahkan bahan emulgator. Pada penelitian ini dipelajari penambahan bahan emulgator/stabilizer yang terdiri dari susu skim, isolat protein kedelai, sodium kaseinat, putih telur dan carboxymethyl cellulose. Selanjutnya konsentrasi emulgator/stabilizer juga dipelajari guna memperoleh emulsi santan yang stabil. Stabilitas emulsi dievaluasi berdasarkan pengamatan visual dengan menentukan parameter persen stabilitas emulsi, pengamatan viskositas emulsi serta mikroskopis guna mengamati ukuran droplet dan sebaran droplet. Hasil penelitian menunjukkan penambahan CMC 1% pada santan yang telah diberi perlakukan pasteurisasi dan penambahan natrium benzoat 0,015% masih menunjukkan stabilitas emulsi yang baik hingga pengamatan hari ke 7. Perubahan fisik santan (warna dan bau) juga tidak berbeda secara siknifikan dibandingkan dengan santan segar.

No abstract