Study of ph effect on the anaerobic-aerobic fermentation of siwalan (Borassus flabellifer l.) sap to produce acetic acid

. Siwalan (Borassus flabellifer L.) is a plant from palm family that is widely found in Tuban, East Java. Siwalan sap has relatively high sugar content of about 10-15 g/100 ml. The sap is obtained by tapping the inflorescences. In general, siwalan sap is used to produce fresh drinks or alcoholic beverages, with maximum storage of 3 days. Due to the sugar content in the siwalan sap, acetic acid products can be made through fermentation of glucose to ethanol. Acetic acid is widely used as a preservative of food and healthy drinks. The purpose of this research was to study the effect of ethanol fermentation of aerobic pH on acetic acid product. Anaerobic fermentation used Saccharomyces cereviceae to produce ethanol, and aerobic fermentation used Acetobacter aceti to produce acetic acid. The aerobic ethanol fermentation used pH 3;3.5;4 and 5. The concentration of ethanol was analyzed using GC ULTRA Scientific Gas Chromatography, DSQ II detector, and MS 220 column. Acetic acid produced from the aerobic fermentation process was analyzed using alkalimetric method. Anaerobic fermentation used Saccharomyces cereviceae with 1-day log phase. Meanwhile, aerobic fermentation used Acetobacter aceti with a 5 day log phase. The highest acetic acid concentration produced from ethanol fermentation was at pH 5 of 2.595%, with the result of acetic acid obtained was 0.519% (b/v).