Cassava starch extraction with a polygalacturonase from a wild yeast strain with disintegration activity on plant tissues.

Abstract

The objective of the present study was to optimize an enzymatic starch extraction process from cassava roots using a polyglacturonase (PGase) from a wild yeast strain (Wickerhanomyces anomalus). The supernatant of W. anomalus culture, with PGase activity, was used as source of enzyme (enzymatic extract, EE). The cassava starch extractions with the EE were done at lab scale and the effects of several factors were studied by using statistical designs. Chemical and functional properties of the starch obtained (enzymatic starch, ES) and those of a commercial starch (CS), were determined. The highest extraction yield was obtained using processed cassava tissues, a solid-liquid ratio of 3:6, EE with an enzyme dosage of 15 EU mL^-1, at 40 °C for 5 h. Proximal analysis of the ES did not show significant differences with the CS. Swelling power and water solubility of ES increased with the temperature up to 70 °C (1.97 gg^-1) and 90 °C (4.27 % w/w), respectively, similar to those of CS. Viscoamylographic profiles of ES showed a pasting temperature of 63.5 °C, a viscosity peak of 422 BU, an stability of the pasta during cooking of 202 BU and a retrograde trend of 98 BU. These values were slightly different compared to those of CS. Clarity assays determined that ES paste is considered a clear or transparent paste. Microscopic evaluation of the ES grains revealed that they were intact without any mechanical damage. The production of cassava starch by enzyme technology seems to be an interesting alternative to the traditional method of extraction by mechanical means, resulting in a novel biotechnological process.