Enhanced ethanol production from Kinnow mandarin (Citrus reticulata) waste via a statistically optimized simultaneous saccharification and fermentation process.

Abstract Dried, ground, and hydrothermally pretreated Kinnow mandarin ( Citrus reticulata ) waste was used to produce ethanol via simultaneous saccharification and fermentation (SSF). Central composite design was used to optimize cellulase and pectinase concentrations, temperature, and time for SSF. The D-limonene concentration determined with high-performance liquid chromatography (HPLC) for fresh, dried, and pretreated biomass was 0.76%, 0.32%, and 0.09% ( v/w ), respectively. Design Expert software suggested that the first-order effect of all four factors and the second-order effect of cellulase and pectinase concentrations were significant for ethanol production. The validation experiment using 6 FPU gds −1 cellulase and 60 IU gds −1 pectinase at 37 °C for 12 h in a laboratory batch fermenter resulted in ethanol concentration and productivity of 42 g L −1 and 3.50 g L −1 h −1 , respectively. Experiments using optimized parameters resulted in an ethanol concentration similar to that predicted by the model equation and also helped reduce fermentation time.