In order to obtain culture of Saccharomyces cerevisiae which has the highest ethanol tolerance and can produce high yield of ethanol as well a study of mutation has been begun. Mutation experiment conducted by continuos adaptation on a chemostat was initiated with a preliminary study of screening of alcohol-tolerant yeast. The procedures of screening of alcohol-tolerant yeast continued by optimation of substrate concentration and determination of its critical pH. Recently, the Laboratory of Microbiology and Bioprocess Technology Faculty of industrial Technology ITB has various kind of yeasts that have been obtained or isolated from various sources. The best culture for mutation has been chosen as the most ethanol tolerant one. By screening them on two types of experiment, has been obtained that culture Saccharomyces cerevisiae R-60 gave the highest external ethanol and internal ethanol as well. External ethanol means the ethanol that was purposely added to the cultivation media, while the internal ethanol means the ethanol that was resulted from fermentation of the yeast. As preparation for mutation experiment, the determination of optimum substrate concentration which can give the highest amount of Saccharomyces cerevisiae cells has been carried out. In order to set up the control point of culture viability on chemostat, the critical pH of choosed culture have also been obtained. The result of the experiment gave optimum glucose concentration of 18.6% and critical pH of 4.5 to 3.8, were to be applied in the mutation process.Keywords: Cultivation; Fermentation; Saccharomyces cerevisiae; Screening; YeastAbstrakPenelitian untuk mendapatkan kultur Saccharomyces cerevisiae yang mempunyai toleransi etanol yang tinggi dan dapat menghasilkan perolehan etanol yang juga tinggi telah dilangsungkan. Percobaan mutasi dilakukan dengan proses adaptasi secara kontinyu dalam chemostat yang diawali dengan suatu studi pendahuluan yang dinamakan skrining ragi tahan etanol. Prosedur skrining ragi tahan etanol ini dilanjutkan dengan optimasi kandungan substrat dan penentuan pH kritis-nya. Pada saat ini Laboratorium Mikrobiology dan Teknologi Bioproses Fakultas Teknologi Industri ITB telah memiliki berbagaijenis ragi yang berasal dari berbagai sumber. Kultur terbaik untuk mutasi dipilih sebagai kultur yang paling toleran terhadap etanol. Melalui percobaan screening ragi tahan etanol yang dilakukan dalam duajenis percobaan, diperoleh bahwa kultur Saccharomyces cerevisiae R-60 memiliki toleransi etanol eksternal dan internal paling tinggi. Etanol eksternal adalah etanol yang sengaja ditambahkan pada media kultivasi ragi, sementara etanol internal adalah etanol yang dihasilkan darijermentasi oleh ragi tersebut. Dalam mempersiapkan percobaan mutasi, penentuan konsentrasi substrat optimum yang dapat menghasilkan jumlah sel Saccharomyces cerevisiae terbesar telah dilakukan. Selain itu titik tetap via bilitas kultur da lam chemostatyang berupa pH kritis kultur pilihan juga telah ditentukan. Dari percobaan pendahuluan mutasi tersebut diperoleh konsentrasi glukosa optimum sebesar 18.6% dan pH ktitis kultur R-60 adalah 4.5 dan 3.8. Data tersebut akan diterapkan pada percobaan mutasi.Kata Kunci: Kultivasi; Fermentasi; Pre-mutasi; Ragi; Saccharomyces cerevisiae
Saccharification of cassava starch using amilase Aspergillus niger ITB CC L74 Bioethanol is a derivative product from cassava that is thoroughly developed nowadays. One of the bioethanol research program of the Chemical Engineering Product Design and Development Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung in the year of 2008 was to increase productivity and the performance of α-amylase and glucoamylase from Aspergillus niger ITB CC L74 for saccharification of cassava starch in bioethanol production. In conjunction with the optimum condition of saccharification process, research on the effect of pH, temperature, Ca2+ concentration, substrate concentration, and enzyme volume percentage have been carried out. The performance of α-amylase was determined by the iodine method while the performance of glucoamylase was done by the Somogyi-Nelson method. Research variable to determine the optimum performance condition of amylase extract were pH (3.15–7.0), temperature (30–89 oC), Ca2+ concentration (0–200 ppm), substrate concentration (0.5–20 %-w/v), and enzyme volume percentage (1.0–50 %-v). The results of this research showed that the optimum performance of amylase complex were pH 4.5, temperature 60 oC, Ca2+ concentration 75 m/L, and substrate concentration 7 %-w/v. The performances of amylase complex increased with the increase in the amount of enzyme percentage, but the increase was limited by the amount of glucose that could inhibit enzyme activity. Keywords: amylase, glucoamylase, Aspergillus niger, saccharification, starch AbstrakBioetanol merupakan produk turunan ubi kayu yang sekarang sedang giat dikembangkan. Salah satu program riset bioetanol Kelompok Keahlian Perancangan dan Pengembangan Produk Teknik Kimia, FTI, ITB tahun 2008 adalah peningkatan produktivitas dan kinerja enzim α-amilase dan glukoamilase Aspergillus niger ITBCC L74 untuk proses sakarifikasi pati ubi kayu pada produksi bioetanol. Sehubungan dengan kondisi optimum proses sakarifikasi, penelitian tentang pengaruh pH, temperatur, konsentrasi Ca2+, konsentrasi substrat, dan persentase volume enzim, telah dilakukan. Analisis kinerja kompleks amilase yang dilakukan meliputi analisis kinerja enzim α-amilase dengan metode iodin dan analisis kinerja enzim glukoamilase dengan metode Somogyi-Nelson. Variabel yang diteliti untuk menentukan kondisi optimum kinerja ekstrak amilase adalah pH (3,5–7,5), temperatur (25–80 oC), konsentrasi Ca2+ (25–200 ppm) konsentrasi substrat (0,5–20 %-b/v) dan persentase volume enzim (1-50 %-v). Hasil penelitian menunjukkan bahwa kinerja kompleks enzim amilase optimum berada pada pH 4,5, temperatur 60 oC, konsentrasi Ca2+ 75 ppm, dan konsentrasi substrat 7 %-b/v. Kinerja kompleks amilase makin baik seiring dengan peningkatan persentase volume enzim, namun peningkatan ini dibatasi oleh kandungan glukosa dalam enzim yang dapat menyebabkan inhibisi terhadap aktivitas enzim.Kata kunci: amilase, glukoamilase, Aspergillus niger, sakarifikasi, pati
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