The present work aims to evaluate on a bench scale, the effects of nitrogen and phosphorous nutrient source concentrations in vinegar production, a process that is used by small scale industries in the State of Paraiba. The response surface methodology has been utilized for modeling and optimization of the fermentation process. Initially a 2³ complete factorial design was used, where the effects of initial concentrations of ethyl alcohol, phosphorous and nitrogen sources were observed. After this analysis the concentration range of the nutrient variables were extended and a two level plus a star configuration factorial experimental design was performed. The experimental values are well represented by the linear and quadratic model equations obtained. The optimum concentration of ethanol was 4% in which the yield and the productivity of the acetic acid were maximized to the values of 70% and 0.87 g L-1 h-1 respectively, for a 24 hours fermentation period. The evaluation of the quadratic models showed that the yield of vinegar is maximized from 28.1 to 51.04% and the productivity from 0.69 to 1.29 g L-1 h-1 when the concentration of the nitrogen nutrient in the medium is increased from 0.2 to 2.3 g mL-1. Thus, at the optimized nitrogen nutrient concentration both the yield and the productivity of the vinegar are increased by 1.85 times.
factorial design; acetic fermentation; ethanol; fermentation process
