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

Abstract

Liquid hot water (LHW) pretreatment associated with high pressure carbon dioxide (HP-CO2) was eval-uated as a potential green pretreatment technology for extraction of hemicelluloses from depithedsugarcane bagasse to produce fermentable sugars. Developing a technology based on the use of lowcost, non-corrosive, and recoverable chemicals as CO2can result in a more efficient and economic pro-cess. In this study, depithed sugarcane bagasse was treated with LHW and HP-CO2at milder temperaturesin comparison with LHW pretreatment alone. To assess the effects of varying pretreatment operationalconditions on extraction of xylo-oligosaccharides and xylose release with cellulose preservation a centralcomposite design (CCD) of experiments was used. The pretreatments were carried out at temperaturesranging from 93.8◦C (8.62 MPa) to 136.2◦C (12.96 MPa) and times from 17.6 to 102.4 min with a liquid-to-solid ratio of 12:1. The maximum xylan and xylose concentrations were achieved by treating depithedbagasse at 100◦C for 30 min and 115◦C for 60 min, respectively. At these conditions the amount of xylanequivalent ranged 10–12 g/L. At 115◦C for 60 min, the cellulose preservation achieved 97.2%. The obtainedresults showed that HP-CO2proved to be an efficient hydrolysis agent. Samples of LHW-HP-CO2pre-treated bagasse were tested for enzymatic digestibility. Depithed bagasse pretreated at 115◦C for 60 minafter enzymatic hydrolysis had a glucose yield of 30.43 g/L and a cellulose conversion of 41.17%.