Processing of cassava waste for improved biomass utilization

Abstract

Cassava ( Manihot esculenta Crantz) pulp is the solid waste produced as a consequence of starch production. This pulp contains a high starch content (50–60% dry basis), causing an environmental problem with disposal. In order to recover this starch, physical or biological treatment of the material must be employed. Pulp was treated either by sonication or incubation with a multi-enzyme mixture of cellulase and pectinase. Both methods were found to improve efficiency of starch extraction by disrupting the complex structure of polysaccharides associated with and entrapping starch granules. In the enzymatic treatment, the content of cellulase and pectinase for high efficiency of starch extraction determined as the yield of liberated starch was investigated using Response Surface Methodology. Use of either cellulase or pectinase alone failed to effectively improve starch extraction. Cellulase concentration seemed to have a greater effect on efficiency of starch yield than pectinase concentration. Treatment of pulp with 15 Novo cellulase units (NCU) of cellulase and 122.5 polygalacturonase (PG) units of pectinase per g dry pulp for 60 min resulted in 40% starch recovery. Quality characteristics of the liberated starch, including paste viscosity (measured by Rapid Visco Analysis) and thermal properties (measured by Differential Scanning Calorimetry) were comparable to a primary starch obtained by root extraction. Susceptibility of the liberated starch to α-amylase was inferior to that of a primary starch. Cellulase and pectinase, however, increased α-amylase susceptibility of the starch remaining in the pulp.