Indo. J. Chem., 2013, 13 (1), 7 - 13 Atmanto Heru Wibowo et al. 7 * Corresponding author. Tel/Fax : +62-858-78677541 Email address : aheruwibowo@yahoo.com THE FERMENTATION OF GREEN ALGAE (Spirogyra majuscule Kuetz) USING IMMOBILIZATION TECHNIQUE OF Ca-ALGINATE FOR Saccharomyces cerevisiae ENTRAPMENT Atmanto Heru Wibowo 1,* , Lailatul Mubarokah 2 , and Adhitasari Suratman 3 1 Central Chemistry Laboratory, University of Sebelas Maret, Jl. Ir. Sutami No. 36 A, Surakarta 57126, Indonesia 2 Department of Chemistry, University of Sebelas Maret, Jl. Ir. Sutami No. 36 A, Surakarta 57126, Indonesia 3 Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara Yogyakarta 55281, Indonesia Received October 29, 2012; Accepted January 26, 2013 ABSTRACT A study of batch fermentation of green algae (Spirogyra majuscula Kuetz) from Pengging Lake, Boyolali, Central Java for bioethanol source using immobilization technique of Ca-alginate for Saccaromyces cerevisiae entrapment has been done. The scope of the study emphasized on the best condition for the processes of hydrolysis and fermentation. Concentration of sulfuric acid and hydrolysis time were varied with 0.1, 0.2, 0.3, 0.4 and 0.5 M for 30, 90, 150, 210, 270, 330, 360, 390, 420, and 450 min to obtain the maximum glucose content of UV analysis. Na- alginate : yeast ratio and fermentation time were varied with 1:5, 2:4, 3:3, 4:2 and 5:1 (w/w) for 1, 2, 3, 4, 5, 6 and 7 days. Distillation at 70–80 °C was deployed to purify the fermentation product. The ethanol content in the product was analyzed using gas chromatography-flame ionization detector (GC-FID). The result of study showed that maximum glucose content was obtained 2.1% from 0.2 M sulfuric acid for 6 h of hydrolysis. Maximum ethanol content was obtained 54.1% from 2:4 ratio of Na-alginate : yeast (w/w) for 4 days of fermentation. The study also concludes that immobilization technique of Ca-alginate increase alcohol content compared to without immobilization of green-algae fermentation. Keywords: Ca-alginate; immobilization; green algae; bioethanol ABSTRAK Telah dilakukan penelitian fermentasi dari alga hijau (Spirogyra majuscula Kuetz) dari danau Pengging, Boyolali, Jawa Tengah sebagai sumber bioetanol dengan teknik imobilisasi Ca-alginat untuk penjebakan Saccaromyces cerevisiae. Lingkup dari penelitian ini menekankan pada kondisi terbaik pada proses-proses hidrolisis dan fermentasinya. Konsentrasi asam sulfat dan waktu hidrolisis divariasikan 0,1, 0,2, 0,3, 0,4, dan 0,5 M selama 30, 90, 150, 210, 270, 330, 360, 390, 420, dan 450 menit untuk mendapatkan kandungan glukosa maksimum dari analisis UV. Rasio dari Na-alginat : ragi dan waktu fermentasi divariasikan dengan perbandingan 1:5, 2:4, 3:3, 4:2 dan 5:1 (b/b) selama 1, 2, 3, 4, 5, 6 dan 7 hari. Distilasi pada 70–80 °C dilakukan untuk memurnikan produk fermentasi. Kandungan etanol dalam produk dianalisis dengan menggunakan kromatografi gas detektor ionisasi nyala (GC-FID). Hasil dari penelitian ini menunjukkan bahwa kandungan glukosa maksimum diperoleh sebanyak 2,1%, yang diperoleh dari hidrolisis 0,2 M asam sulfat selama 6 jam. Kandungan etanol maksimum sebanyak 54,1%, yang diperoleh dari fermentasi dengan perbandingan 2:4 dari Na-alginat : ragi (b/b) selama 4 hari. Penelitian ini juga menyimpulkan bahwa teknik imobilisasi Ca-alginat meningkatkan kandungan alkohol dibandingkan dengan tanpa imobilisasi dari fermentasi alga hijau. Kata Kunci: Ca-alginat; imobillisasi; alga hijau; bioetanol INTRODUCTION The depletion of fossil fuel is a problem related to the energy source. On the other hand, fossil fuel as energy source has caused accumulation of carbon dioxide in the atmosphere or environment [1]. These problems should be solved by seeking alternative sources that is environmentally friendly. Biofuel is one of the alternative sources. Production of biofuel from renewable sources is one of the most sustainable alternatives to petroleum fuels and a viable means for environmental and economic sustainability [2].