Fermentation of Raw Cassava Starch Using Geotrichum candidum sp. Optimizing enzyme and starch concentrations for alcohol production

Production of bioethanol is a global requirement toaddress the question of energy crisis. Attempts have been madeto use agricultural starch based renewable resources to produceethanol. Starchy materials should be converted into simplersugars prior to fermentation and this is achieved by treating withenzymes. Fermentation medium containing 1.5 g, 3 g and 10 g ofraw cassava were optimized for brix value by directly inoculatingsamples (DIS) with fungi G. candidum or treating the mediumwith different concentrations of crude enzyme (50 mL & 100 mL)and 50% ammonium sulphate fractionated proteins (EnzymeTreated Samples -ETS). Highest brix values containing samplesfor 1.5 g, 3 g and 10 g of cassava under two differentexperimental conditions were ETS1, ETS2, ETS3, and DIS1,DIS2, DIS3 respectively. The samples were fermented with yeaststock cultures of maximum viable cells (7.065×106 cells cm-3&86.4% viability). Brix value and alcohol percentage for thesesix samples showed that 50% Ammonium sulphate saturatedenzyme samples is suitable to obtain higher brix value whencompared to crude and direct inoculation method. Then theculture conditions were optimized for starch percentage, pH andviable cell numbers. The results showed that an effective increasein Brix value of 2.3 could be obtained with 3 % and 4 % starchafter 12 hrs incubation period when treated with 50%ammonium sulphate fractionated enzyme. Optimizedfermentation conditions showed that the viable cell numbers ofculture medium decreased during 36-48 hrs of incubation period.There was a sudden pH drop after 12 hrs and considerablechanges were not observable in prolonged incubation.Optimization results for alcohol with 4 % starch showed that ahigh percentage of alcohol (2.5 %) could be obtained after 60 hrsincubation. In conclusion, 50% saturated enzyme sample at roomtemperature and 4% starch has yielded highest brix value andresulted 2.5% of alcohol in 100 mL of fermentation medium