Xylitol production by Ca-alginate entrapped cells: comparison of different fermentation systems

Candida guilliermondii cells were entrapped in Ca-alginate beads and used for xylitol production from concentrated sugarcane bagasse hemicellulosic hydrolysate in three different fermentation systems, namely 125-ml Erlenmeyer flasks (EF), 2.4-1 stirred tank reactor (STR) and 2.4-1 basket-type stirred tank reactor (BSTR). The EF system provided a xylitol production of 21.0 g(P) l(-1), a product yield based on xylose consumption of 0.54 g(P) g(S) (-1), and an overall production rate of 0.44 g(P) l(-1) h(-1) after 48 h of fermentation. By the STR system, 23.5 g(P) l(-1) was produced after 60 h of fermentation, corresponding to a yield of 0.58 g(P) g(S) (-1) and a production rate of 0.39 g(P) l(-1) h(-1). As the average volume of the beads decreased by 10.7% (p < 0.05) during this fermentation, a basket was fitted into the reactor vessel to prevent the beads abrasion and thus maintain their integrity. However, the xylitol yield (0.46 g(P) g(S) (-1)), production rate (0.21 g(P) l(-1) h(-1)) and concentration (15.0 g(P) l(-1)) attained by this system were affected by mass-transfer limitations. (C) 2003 Elsevier Science Inc. All rights reserved.