Production of Baker`s Yeast (Saccharomyces cerevisiae) from Raw Cassava Starch Hydrolyzates in a Bioreactor under Batch Process

Bioconversion of raw cassava starch into value-added product was investigated. This involved hydrolysis of extracted starch from freshly harvested cassava tubers using three different methods. Enzyme-enzyme hydrolysis method gave the highest Dextrose Equivalent (DE) of 34 with starch conversion efficiency of 87.3% followed by the acid-enzyme hydrolysis which gave DE of 29.75 with conversion efficiency of 76%, while the lowest yield of DE 24.5 with conversion efficiency of 63% was recorded when acid hydrolysis method was employed. The cassava starch hydrolyzates obtained were used as feedstocks for the aerobic cultivations of the Saccharomyces cerevisiae under batch conditions for 48 h. The results obtained show that the hydrolyzates supported the growth of the microorganism. Biomass yields (YX/S) obtained for the three cultivations carried out using hydrolyzates from acid, acid-enzyme and enzyme-enzyme hydrolysis of raw cassava starch were 0.472, 0.462 and 0.470 g g-1, respectively. Maintenance coefficient (me) obtained for the three cultivations were 0.0047, 0.0135 and 0.003 h-1 in the same order. These low values of maintenance energy is an indication of non-stressful metabolism by the microorganism in this batch system as the magnitude of the maintenance energy is strongly linked to the environmental conditions and the ability of the microorganism to survive in it.