Aspects of the Cell Growth of Candida guilliermondii in Sugar Cane Bagasse Hydrolysate M. Molwitz3, S. S. Silvab, J. D. Ribeiro , I. C. Roberto , M. G. A. Felipe , A. M. R. Pratab and I. M. Mancilhab a Hochschule für Technik - Fachhochschule Mannheim - Fachbereich Biotechnologie, Windeckstraße 110. 68163 Mannheim. Bundesrepublik Deutschland h Faculdade de Engenharia Quimica de Lorena-Centro de Biotecnologia e Quimica-Rodovia Itajubä-Lorena, Lorena S.P. Brazil Z. Naturforsch. 51c, 404-408 (1996); received October 30/December 20. 1995 Candida guilliermondii, Oxygen, Sugar Cane Bagasse, Xylose, Xylitol Fermentation In this work the behavior of the growth of Candida guilliermondii FTI 20037 in sugar cane bagasse hemicellulosic hydrolysate on various oxygen transfer rates was investigated. The yeast was able to grow and produced xylitol at different performence levels. At 1.0 vvm (volume of air per volume of medium per minute) the highest growth with 24.4 g/1 was observed, but no xylitol was produced. At aeration rate of 0.5 vvm the growth was lower, but therefore slight amounts of xylitol (xylitol yield factor - yp/s = 0.15 g/g) were observed. The lowest cell concentration (10.7 g/1) and the highest xylitol yield ( Y p/s = 0.46 g/g) was observed when aeration was changed from 0.5 vvm to 0.05 vvm after 14 h. Introduction Lignocellulosic biomass from agriculture and forestry residues like rice husk, eucalyptus and sugar cane bagasse, are the most abundants or ganic compounds in the biosphere, with an annual production of approximately 50xl09 tons (Lutzen et cd., 1981). Every year large amounts of waste biomass is accumulated in Nature, which causes great environmental pollution problems and a loss of potential valuable resources. Based on these facts it becomes necessary to find new technol ogies to use this renewable feedstock in different processes to produce economically valuable pro ducts. The biotechnological approach is one way to make this biomass an important substrate for microorganisms for production of several useful feedstocks such as ethanol, xylitol and 2,3-bu- tanediol. Xylitol is a sugar-alcohol of high eco nomical value that can be produced from lignocel lulosic biomass by biotechnological means, and presents some important chemical properties such as sweetening power comparable to that of sucrose as well as anticariogenic effects (Aguirre-Zero et Reprint requests to Prof. Dr. S. S. Silva. Telefax (0125)-533116. cd., 1993). Furthermore, the human metabolism of xylitol is insulin independent; therefore it is well suited as a substitute of sucrose in cases of diabe tes (Bär, 1986). The use of lignocellulosic residues as substrate in fermentative processes for xylitol production consists initially in releasing sugars from the hemicellulose portion of this biomass through a mild acid hydrolysis process. This pro cess is accompanied by the formation of apprecia ble amounts of hemicellulose decomposition pro ducts, such as furfural, hydroxymethylfurfural, acetic acid and other products derived from lignin degradation (Haying, 1981). These chemicals in terfere negatively on the yeast cell growth and in additional xylitol fermentation. Thus, the use of this biomass hydrolysate as a fermentation me dium for microorganism growth is critical and sev eral treatments are necessary for removing these products. The performance of the cell growth on this hydrolysate and the xylitol formation depends on the treatment employed and the fermentation conditions used. In this communication we present a simple method of treatment of sugar cane ba gasse hemicellulosic hydrolysate and some aspects of Candida guillermondii FTI 20037 growth in this biomass under different 0 2 conditions, since the oxygen supply is the most important parameter af fecting xylose fermentation. 0939-5075/96/0500-0404 $ 06.00 © 1996 Verlag der Zeitschrift für Naturforschung. All rights reserved. D