Utilization of Cassava Fibrous Residue for the Production of Glucose and High Fructose Syrup

Abstract

Cassava (Manihot esculenta Crantz) is one of the largest sources of starch and sago. The cassava fibrous residue (CFR) contains 61%-63% starch and other polysaccharides and causes major disposal problems. Due to its high starch content, it can be utilized to obtain value-added products. Work was therefore undertaken to obtain glucose syrup by hydrolyzing starch and cellulose with various enzyme treatments, followed by conversion to high fructose syrup. Standardization of various conditions for hydrolysis was determined. A combination of α-amylase and glucoamylase (T1 & T2) resulted in 52.88–54.24% conversion of CFR to glucose. The yield could be enhanced to 58.70–60.00% by adding cellulase enzyme complex, Accellerase 1000, in combination with α-amylase and glucoamylase. Cellulase activity helped to reduce viscosity of the CFR slurry and also improved the starch hydrolysis by α-amylase and glucoamylase. The most suitable enzyme treatment was found to be simultaneous hydrolysis of CFR with glucoamylase, Dextrozyme GA and cellulase enzyme Accellerase 1000 at pH 4.5 and 60°C for 48h, followed by a one hour liquefaction with α-amylase, Liquezyme X (T5). Because of the high fiber content, it was not possible to handle a slurry containing more than 15% of the material, as per the reports of earlier workers. However, hydrolysis of CFR at different substrate concentrations in the present study indicate that hydrolysis of a higher substrate concentration, i.e., 25%, was possible with this enzyme treatment. Production of high fructose syrup from higher slurry concentrations reduces the cost of concentrating glucose syrup. Results obtained for saccharification and isomerization of two different samples of cassava fibrous residue indicated that the yield of glucose and fructose depended on the starch content in the initial raw material.