Ethanol Production from Starch Hydrolyzates using Zymomonas mobilis and Glucoamylase Entrapped in Polyvinylalcohol Hydrogel

Abstract

The glucoamylase from Aspergillus niger, immobilized into poly(vinylalcohol) hydrogel lens-shaped capsules LentiKats®, was used for simultaneous saccharification and fermentation (SSF) with Zymomonas mobilis in free form. This system was stable in both the repeated batch and continuous mode of SSF. The microorganism was found to adsorb on the capsules with immobilized enzyme. This increased the ethanol productivity of the repeated batch system with 5% w/v of immobilized glucoamylase almost 2.1 times (7.2 g l⁻¹ h⁻¹) compared to free enzyme–free microorganism system (3.5 g l⁻¹ h⁻¹). The continuous SSF with the immobilized glucoamylase (11.5% w/v) tested for 15 days had productivity 10 g l⁻¹ h⁻¹, which is comparable to continuous experiments on semi-defined glucose medium (10 g l⁻¹ h⁻¹). These two systems were stable in both glucoamylase activity and microorganism productivity.