Continuous Bioethanol Production Using Saccharomyces cerevisiae Cells Immobilized In Nata De Coco (Biocellulose) Charlimagne M. Montealegre, Emerson R. Dionisio, Lawrence V. Sumera, Jay R T. Adolacion and Rizalinda L. De Leon + Biochemical Engineering Laboratory, Department of Chemical Engineering, College of Engineering, University of the Philipines, Diliman, Quezon City 1101 Philippines Abstract. The performance of Nata de coco (NDC) and Calcium alginate (CA) as an immobilization medium for Saccharomyces cerevisiae cells are compared in terms of production rate and conversion. S. cerevisiae cells are immobilized in NDC and CA beads using a cell suspension with an average approximate live cell density of 232.1288 ± 1.5387 cells/mL. The biocatalysts NDC and CA are charged into horizontal fermentation reactors. A centrifugal pump and manifold is used to control the flow rate to a desired flow rate of 9 mL/hr. Samples are collected every 12 hours and tested for ethanol by gas chromatography and glucose concentration by colorimetry. The average steady state effluent ethanol concentration, productivity and conversion in NDC are 5.093 % by volume, 52.329 mL/hr and 0.7779, respectively. One-way ANOVA showed that the immobilization medium has a significant effect on the parameters under consideration. T-test is further performed between NDC and CA biocatalysts which showed that effluent ethanol concentration, productivity and conversion of NDC and CA are statistically equal. The study showed that the NDC biocatalyst performs equally well in the conditions optimized for CA biocatalyst. The structural strength and cost effectiveness of Nata de Coco makes it a very promising immobilization medium for continuous bioethanol production. Keywords: Immobilization, Biocellulose, Calcium Alginate, Continuous Fermentation, Horizontal Reactor, Baker’s Yeast 1. Introduction Continuous fermentation systems offer important economic advantages and significantly improves production rate. In freely suspended cell systems, continuous operation is limited by flow rate as cells are carried in the effluent resulting to a decrease or complete loss of cells. Cell immobilization supports the cells promoting operation at higher flow rates. Immobilization is achieved by various mechanisms. One of which is surface adsorption where cells naturally adhere to the surface of the material through electrostatic force. Yeast cells are adsorbed in the surface of NDC which is a very hydrophilic and strong material with a young's modulus comparable to aluminum (Titech, 2001). Studies on optimization of the immobilization process are reported in the literature (Nguyen, Ton, & Le, 2009). In another mechanism, matrix encapsulation, cells are trapped in a polymer matrix of materials such as alginate and carrageenan. Entrapment in CA is commonly used in studies with ethanol fermentation due to “the requirement for mild conditions and the simplicity of the used procedure” (Ramakrishna & Prakasham). Several disadvantages in immobilization with CA include damage to gel particles due to carbon dioxide, “diffusion limitations of nutrients, metabolites and oxygen due to the gel matrix and the high cell densities in the gel beads, the chemical and physical instability of the gel and the non-regenerability of the beads, making this immobilization type rather expensive” (Verbelen, De Schutter, Delvaux, Vestrepen, & Delvaux, 2006). Carbon dioxide production decreases the working volume of the reactor thereby reducing its fermentative + Corresponding author. Tel.: + 6329296640; fax: +6329296640. E-mail address: rldeleon@up.edu.ph. 77 2012 2nd International Conference on Environment and Industrial Innovation IPCBEE vol.35 (2012) © (2012) IACSIT Press, Singapore