Effect of SO 2, NaOH and Na 2CO 3 pretreatments on the degradability and cellulase digestibility of grape marc

Abstract

As part of research on the utilization of grape marc as a carbon source for single cell protein (SCP) production, virgin grape marc (VM) and exhausted grape marc (EM) were pretreated at high temperature with water, SO 2, Na 2CO 3 and NaOH solutions in various concentrations. The effect of these treatments was determined by measures of dry matter, nitrogen, ADF, lignin and cellulose, as well as of total cellulase digestibility on the residual grape marcs. The drying of original marc, even at 70°C, severely affected the susceptibility to degradation of lignocellulosic materials (LCM). Therefore storage in a damp state is necessary. The addition of Na 2CO 3 (about 10% on dry matter) served this purpose and also acted as an efficient pretreatment agent. NaOH (1%) solution at 120°C caused the greatest degrading effects, but also a notable solubilization of nitrogen compounds; 1·5% SO 2 solution at 100°C had a good effect on VM but not on EM; 0·5% NaOH solution and 1·0% Na 2CO 3 solution showed intermediate features.