Optimization of Palmyra palmsap fermentation using co-culture of Saccharomyces cerevisiae and Pichia stipitis

Palmyra palm sap whose main sugar components can be used for the food grade ethanol feedstock is potential to increase economic value. Therefore, its production process needs to be improved especially in fermentation process. This study aims to investigate the best condition of the fermentation of palmyra palm sap to be ethanol using co-culture of Saccharomyces cerevisiae and Pichia stipitisin different variables such as pH, initial inoculum and sugar concentration to get the best ethanol fermentation yield. The experiment was designed using statistical method which is Response Surface Methodology (RSM) and carried out in batch-wise with a working volume of 100 mL for 80 hours. The coefficient of pH and inoculum as a linear form and all quadratic coefficients have remarkable effect on the ethanol yield (P value < 0.05). The fit of model gave high value of R² of 0.983, indicated that 98.3% of the variability in the response could be explained by the model. The highest ethanol yield was obtained 0.32 (g ethanol/g total sugar) with efficiency = 65.42% at pH 5.28, inoculum concentration of 6658612(cell.ml^-1)/(g.l^-1), and sugar concentration of 120 g/l.