Considering the capacity of Zymomonas mobilis ATCC29191 bacteria to produce sorbitol from fructose sources and the importance of difference factors in the fermentation process, the objective of this study was the development of a mixed modeling matrix to assess the effect of the sucrose concentration, fermentation time and type of process on sorbitol production by Zymomonas mobilis ATCC29191. The experiments were performed in times 12, 24 and 36 h, containing 200, 250 and 300 g/L sucrose. The fermentative process was analysed with free and immobilized cells. The sucrose concentration was not a relevant factor for the process but the fermentation time and the type of process were significant. The use of cells in the immobilized form and the 36 h time period presented maximum sorbitol productions. The production with immobilization was practically twice that obtained with free cells, increasing of 25 g/L with free cells for 50 g/L with immobilized cells. Thus, a model was developed with reasonable predictive capacity for sorbitol production. Zymomonas mobilis ATCC 29191 could be immobilized in Luffa cylindrica after adding chitosan for cell flocculation. (C) 2005 Elsevier Ltd. All rights reserved.