The aim of this investigation was to optimize immobilization conditions to entrap Kluyveromyces marxianus DBKKUY-103 during ethanol fermentation from sweet sorghum juice using a response surface methodology. The effects and interactions of variables involved in cell entrapment using polyvinyl alcohol and sodium alginate were studied through a fractional factorial design. The results suggested that the primary variables involved in cell entrapment that significantly affected ethanol fermentation were sodium sulfate concentration, polyvinyl alcohol, and sodium alginate contents (P < 0.01). Subsequently, these variables were optimized for the preparation of cell entrapment based on response surface methodology and using central composite design. The results indicate that cell entrapment can achieve an ethanol concentration of 81.56 g L -1 under the following optimal conditions: bead gel diameter of 4.0 mm, calcium chloride concentration of 0.3 M, polyvinyl alcohol content of 10.09% (w v -1 ), sodium alginate content of 3.39% (w v -1 ), and sodium sulfate concentration of 0.44 M. Furthermore, statistical analysis of the model reveals that it adequately fit the experimental data (P < 0.01, R 2 = 0.9879). Therefore, this model can be used to efficiently prepare entrapped cells for ethanol production.

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