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

Abstract

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-l stirred tank reactor (STR) and 2.4-l 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.