Bioethanol production from sunflower stalk: application of chemical and biological pretreatments by response surface methodology (RSM)

Abstract

The present paper discusses response surface methodology (RSM) as an efficient tactic for predictive model and optimization of the whole experimental methods of reducing sugar and energy. In this work, the application of RSM presented for optimizing reducing sugar and energy as compared with production between chemical and biological pretreatments. All experiments applied statistical designs in order to develop a statistic multivariate analysis model that provides to consider the effect of different parameters on a process and describe the optimum values of these variables to optimize the response. Dred sunflower stalks were pretreated by sodium hydroxide (NaOH) and Trichoderma reesei as a function of two variables: concentration of NaOH (%) and T. reesei (%) and time for pretreatment (Day) to receive reducing sugar and energy. The chemical pretreatment model was characterized by 13 runs, varying the variables at two factors, NaOH (1, 1.5, 2%) and Day (1, 2, 3). The biological pretreatment model was characterized by 13 runs, varying the variables at two factors, T. reesei (1, 1.5, 2%) and Day (1, 2, 3), by central composite design experimental design. In the chemical pretreatment, experiments performed at 2% (w/v) of NaOH for 3 days were used. The chemical pretreatment model at 2% NaOH for a 3-day release reduced sugar by 5.812 g/L and energy by 92.992 kJ/L; on the other hand, biological pretreatment model at 2% T. reesei for a 3-day release reduced sugar by 3.891 g/L and energy by 62.256 kJ/L, reducing sugar starter for fermentation by 49.0670 ± 6.4660 g/L and fermentation efficiency by 71.60% at 48 h fermented time.