Fed-batch Alcoholic Fermentation of Palm Juice (Arenga pinnata Merr): Influence of the Feeding Rate on Yeast, Yield and Productivity

摘要

In North Sulawesi has been known a very potential crop for yielding bio ethanol, is palm crop. Palm crops more productive than cane in yielding sugar and biofuel per hectare. Its productivity about 4 - 8 times compared to cane, and its sugar rendement 14%, while cane only 7%. Based on this research were obtained the tapping process should be conducted by unique sequential steps in order to reach pH 8 and sugar concentration (brix) 12 – 14 % of juice. Alcohol is a chemical was produced from crops like cassava, corn, sago and was usually named as bio ethanol. Cassava, corn and sago is food crops which is ordinary to be planted by people almost in all Indonesia region, but in North Sulawesi Province were very potential crops and have some excellences compared to other crops in yielding bioethanol, that is palm crops. The tap is a good substance for alcohol fermentation due to its high sugar and low ash contents. The objective of this study to support procurement of energy alternative.and production of bioethanol 99.5% The process of alcohol fermentation was conducted in a bottle glass under an aerobic conditions and at room temperature. The substances of fermentation process consist of 500 ml arenga pinnata sap and starter, solution of NPK and the bread yeast can be added when necessary. The fermentation process was carried out in several treatment methods and the treatment was based on the fermentation subctances used. The differences between the treatment methods: P-1, P-2, P-3 and P-4 are in the percentages of palm juice volume (%): 86, 90, 75 and 75, starter volume (%): 14, 10, 25 and 25 and NPK addition (%): 0.4, 0.4, 0.4 and 0.4 and 5% bread yeast. The fermentation of arenga pinnata sap was conducted batch system in room temperature during 24 hours incubation. Fermentation activities are monitored by some perameter such as microbial population, alcohol content, sugar content. The result shows that the palm juice is a good feedstock for fermented bioethanol. The best yield is obtained by fermentation of feedstock containing 25% starter, 0.4% NPK solution, and 5% bread yeast and bio ethanol concentration is about 12% (89% bioethanol content of feedstock). By using of Saccharomyces serevisiae was obtained ferment liquor with alcohol rate from 12% - 14% and purity about 35 – 42 %. By using of reflux distillation and purification fuel grade bioethanol by absorbtion technique with zeolite and CaO was resulted the purity of bioethanol 90% - 96% until 99.5%. The highest purity was 96% by maintaining the column temperature of 760C while purity of 93% was of 76,50C. The flow rate of bio ethanol also was from 0.6 liter to 1 liter /hour by varying column temperature from 76 to 78oC and bioethanol 99.5 % : 100 liter per day.