The environmentally-friendly, economically-viable production of ethanol from cellulosic biomass remains a major contemporary challenge. Much work has been done on the disruption of cellulosic biomass structure, the production of enzymes for the conversion of cellulose and hemicellulose into simple sugars that can be fermented by bacteria or yeast, and the metabolic engineering of ethanol producing microbes. The results of these studies have enabled the transition from laboratory to industrial scale of cellulosic ethanol production. Notably, however, current processes use free microbial cells in batch reactors. This review highlights the advantages of using immobilized and co-immobilized cells together with continuous bioreactor configurations. These developments have the potential to improve both the yield and the green credentials of cellulosic ethanol production in modern industrial settings. (C) 2019 Elsevier Ltd. All rights reserved.