Abstract:
This research was to study the production of ethanol by co-cultivation between amylolytic and ethanol producing microorganism. The grain sorghum used as a raw material in this study is an alternative crop that can withstand drought, yield up to 3-4 times a year and is a cereal with high starch content. The conversion of starch in the heat pretreated grain sorghum to sugar by 3 strains of amylolytic microorganisms was compared. The results showed that the optimal enzyme activity of Aspergillus oryzae TISTR 3086 and Basillus amyloliquefaciens TISTR 1045 at 24 hours were 14.363 U/ml and 7.475 U/ml, respectively, while Saccharomycopsis fibuligera TISTR 5033 was 1.688 U/ml. Study the optimal conditions for amylylolytic production with Random block design (RBD), the amount of grain sorghum was 15 percent with a nitrogen source (NH4)2SO4 0.5 percent for A. oryzae TISTR 3086 and B. amyloliquefaciens TISTR 1045. The highest enzyme activity was 18.003 and 12.548 U/ml, respectively. Then Plakett-Burman method and Response surface method (RSM) were used for optimizing the type and quantity of mineral sources. The results showed that for A. oryzae TISTR 3086 was (NH4)2SO4 5.97 g/l, KH2PO4, 3.33 g/l, CaCl2 1.97 g/l and FeSO40.14 g/l, while for B. amyloliquefaciens TISTR 1045 was (NH4)2SO4 6.57 g/l, KH2PO4 3.00 g/l, MgSO4 1.02 g/l and NaCl 2.53 g/l. The equivalent point represented the highest enzyme activity was 21.6304 and 15.4807 U/ml. respectively. Further study, the potential amylolytic producing strain was co-cultivation with ethanol producing microorganism. The result showed that at 48 hours, 14.3244 g/l of ethanol was obtained from co-cultivation between A. oryzae TISTR 3086 and Saccharomyces cerevisiae. The optimal co-cultivation condition was studied using Plakett-Burman method and RSM method. From the statistical analysis, the equivalent points; the time to inoculate S. cerevisiae at 23.8298 hour and the amount of inoculum of 15.1914 percent gave 16.1317 g/l of ethanol at 48 hours. The experiment was carried out for validation at the equivalent points the actual 16.6762 g/l ethanol and the 0.3474 grams per liter per hour of productivity were obtained.