1. Department of Chemical Engineering, Cape Peninsula University of Technology, P. O. Box 652, Cape Town 8000, South Africa
2. Bioresource Engineering Research Group (BioERG), Faculty of Applied Sciences, Cape Peninsula University of Technology, P. O. Box 652, Cape Town 8000, South Africa
3. School of Chemical and Minerals Engineering, North West University, Private BagX1290, Potchefstroom, 2520, South Africa