Increasing of raw starch hydrolyzation in cassava tuber using fungal pectinase
1992
Polson Makakhan
Eleven strains of Aspergillus spp and 3 strains of Rhizopus spp efficient in raw cassava starch hydrolysis were found to be good pectinase producers as well. Strain selection was performed using solid substrate fermentation. Among those strains, Rhizopus sp 26R gave the highest pectinase activity. Optimization conditions of the pectinase enzymes production were obtained on substrates containing 20 g of the mixture of wheat bran, rice bran and rice husk in a ratio of 6:12:2 in a 9X14 inches plastic bag which moisture content was initially adjusted to 58 %, initial pH of the substrate was 5.7 and the incubation temperature was 32 deg C. The highest activity of the enzymes could be detected in 6-7 days. Under these conditions, Rhizopus sp 26R produced in 6-7 days. Under these conditions, Rhizopus sp 26R produced ca 700 units of pectinases per gram of wet substrates. The pectinases produced by Rhizopus sp 26R could, by itself, hydrolyze raw starch from cassava tuber. Moreover, when these enzymes were mixed with crude Glucoamylase which produced by Aspergillus sp J8, the efficiency of hydrolysis of raw starch from the ground cassava tuber was significantly increased. Partial purification of the pectinases of Rhizopus sp 26R was done through several steps. Two hundred thirty nine units/ml of the crude enzymes were precipitated with 60-90 % (NH5)2SO4. Then, the concentrated enzymes were purified through DEAE Cellulose, CM cellulose ion-exchsng chromatographs and Toyopearl HW 55 gel filtration chromatographys, respectively. The enzymes were partially purified to 100 times with specific activity of 3,889 units/mg protein. By these steps of purification approximately 2 % of the enzymes were recovered.
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