Enhancing liquid hot water (LHW) pretreatment of sugarcane bagasse by high pressure carbon dioxide (HP-CO2)

Abstract

Liquid hot water (LHW) pretreatment associated with high pressure carbon dioxide (HP-CO2) was evaluated as a potential green pretreatment technology for extraction of hemicelluloses from depithed sugarcane bagasse to produce fermentable sugars. Developing a technology based on the use of low cost, non-corrosive, and recoverable chemicals as CO2 can result in a more efficient and economic process. In this study, depithed sugarcane bagasse was treated with LHW and HP-CO2 at milder temperatures in comparison with LHW pretreatment alone. To assess the effects of varying pretreatment operational conditions on extraction of xylo-oligosaccharides and xylose release with cellulose preservation a central composite design (CCD) of experiments was used. The pretreatments were carried out at temperatures ranging from 93.8°C (8.62MPa) to 136.2°C (12.96MPa) and times from 17.6 to 102.4min with a liquid-to-solid ratio of 12:1. The maximum xylan and xylose concentrations were achieved by treating depithed bagasse at 100°C for 30min and 115°C for 60min, respectively. At these conditions the amount of xylan equivalent ranged 10–12g/L. At 115°C for 60min, the cellulose preservation achieved 97.2%. The obtained results showed that HP-CO2 proved to be an efficient hydrolysis agent. Samples of LHW-HP-CO2 pretreated bagasse were tested for enzymatic digestibility. Depithed bagasse pretreated at 115°C for 60min after enzymatic hydrolysis had a glucose yield of 30.43g/L and a cellulose conversion of 41.17%.