Enzymatic hydrolysis of cellulose and the use of TiO2 nanoparticles to open up the cellulose structure

Abstract

A major barrier in the process of cellulose enzymatic hydrolysis into glucose for biofuel production is the enzyme accessibility to cellulose. In this study, a new cellulose regeneration strategy is developed to address this problem. In this strategy, cellulose is dissolved and then regenerated in a networked form. The networked cellulose (NC) was prepared with a high yield via 70% sulfuric acid dissolution of microcrystalline cellulose (MCC) followed by regeneration with ethanol. The material was studied as a possible and easily accessible source of glucose. Washed, dialyzed and freeze-dried NC samples were enzymatically hydrolyzed to glucose. The networked cellulose showed improved enzymatic hydrolysis rate compared to microcrystalline cellulose. With enzyme concentration of 2 mg/mL, the networked cellulose had conversion of 72.8% (wt%) into glucose compared to 33.7% for untreated microcrystalline cellulose. To further increase the enzymatic accessibility, NC was co-regenerated in the presence of TiO2 nanoparticles. SEM images revealed that TiO2 particles helped in opening up cellulose structure through the co-regeneration process. Different NC-TiO2 materials were prepared with different TiO2 percentages. The measured rates of hydrolysis showed that TiO2 inclusion significantly improved the enzymatic hydrolysis, especially at a 50 mg/mL TiO2 concentration. 92.3% conversion of cellulose to glucose was achieved.