Cold enzymatic hydrolysis conditions for bioethanol production were optimized using multi-objective optimization. Response surface methodology was used to optimize the effects of a-amylase, glucoamylase, liquefaction temperature and liquefaction time on S. cerevisiae biomass, ethanol concentration and starch utilization ratio. The optimum hydrolysis conditions were: 224 IU/g(starch) alpha-amylase, 694 IU/gstarch glucoamylase, 77 degrees C and 104 min for biomass; 264 IU/g(starch) alpha-amylase, 392 IU/g(starch), glucoamylase, 60 degrees C and 85 min for ethanol concentration; 214IU/g(starch) alpha-amylase. 398IU/g(starch) glucoamylase, 79 degrees C and 117 min for starch utilization ratio. The hydrolysis conditions were subsequently evaluated by multi-objectives optimization utilizing the weighted coefficient methods. The Pareto solutions for biomass (3.655-4.380 x 10(8) cells/ml), ethanol concentration (15.96-18.25 wt.%) and starch utilization ratio (92.50-94.64%) were obtained. The optimized conditions were shown to be feasible and reliable through verification tests. This kind of multi-objective optimization is of potential importance in industrial bioethanol production. (C) 2011 Elsevier Ltd. All rights reserved.