Efficient hydrolysis of glycogen from engineered Synechocystis sp. PCC 6803 catalyzed by recyclable surface functionalized nanoparticles for ethanol production

Abstract The availability of sugars is a key factor for industrial ethanol production. In this study, recyclable surface functionalized metal oxides were prepared and used as catalysts to obtain sugars directly from engineered Synechocystis sp. PCC 6803 (hereafter Synechocystis) biomass. The individual, sulphonated and tungstenated forms of Al2O3, CaO, Fe3O4, TiO2 and ZrO2 were screened for the hydrolysis of Synechocystis glycogen under ultrasound irradiation. Among them, the sulphonated ZrO2 produced a maximum fermentable sugar yield of 40.2 g/L, whereas the tungstenated ZrO2 produced 37.8 g/L. This improvement was due to the combined action of ultrasound irradiation and acidic groups conferred by sulphur or tungsten on metal oxides. In recycling, tungstenated metal oxides were superior to sulphonated metal oxides in terms of recovery and hydrolysis efficiency. The compatibility of the tungstenated metal oxides mediated hydrolysis with fermentation using Saccharomyces cerevisiae MTCC-170 produced the highest ethanol concentration (16.5 g/L), which favors the overall process.