Acidic and enzymatic hydrolysis of glucomannan agroindustrial waste

Abstract

Processing iles-iles tubers (Amorphophallus onchophyllus) into glucomannan flour leaves waste in the form of solid powder which is a by-product of the glucomannan separation process. The waste contains starch, fiber, and the remaining glucomannan which can still be used as simple sugar through hydrolysis. The purpose of this study is to examine the hydrolysis process of glucomannan agro-industrial waste using acidic and enzymatic methods as a comparison and to determine its effect on the products and by-products formed. Acid hydrolysis using conventional heating (autoclaves) and microwaves with dilute acids, HCl and H2SO4 at concentrations of 0.5 M and 1 M. Enzymatic hydrolysis using a consortium of α-amylase (1.75 and 3.5 U/g), amyloglucosidase (0.3 and 0.6 U/g), and cellulase (1 and 2 U/g). The results showed the potential of waste with the main components consisting of starch (47.26 ± 0.29%), fiber (15.79 ± 0.62%), residual glucomannan (12.64 ± 0.26%). Acid hydrolysis using HCl (0.40-0.56 g sugar/g dry matter) results slightly higher than H2SO4 (0.43-0.53 g sugar/g dry matter). Autoclaves hydrolysis produces sugars with a high DE (76.08-100.18), but with a lower yield (35.90-40.50 %), while the microwave hydrolysis produces sugars with a DP (1.62-2.22) and a higher yield. The higher the concentration of acid, the reducing sugar value, DE, and the higher HMF, but lower DP. In enzymatic hydrolysis, an increase in enzyme dose gives results that are not significantly different. The best treatment is obtained from enzymatic hydrolysis with normal doses because it has a reducing sugar (0.43 g reducing sugar/g dry matter) and total sugar (0.66 g sugar/g dry matter) high and a low HMF (0.19 mg HMF/g dry matter).