Optimization of dilute acid and hot water pretreatment of different lignocellulosic biomass: A comparative study

Pretreatment of biomass to alter their recalcitrant structures is an essential step to obtain high yield of products via bioconversion processes. In this study, main emphasis was to compare the results evaluated in terms of total reducing sugars (TRS) yield after acid and hot water pre-treatment process performed with laboratory scale equipment using different lignocellulosic biomass. The biomass chosen for this purpose i.e. sugarcane bagasse and bamboo were collected from Guwahati, Assam and their physico-chemical characteristics were examined using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA) including proximate and ultimate analysis. Crystalinity of the biomass used was observed to be 33.15% and 31.29% for sugarcane bagasse and bamboo respectively. Hot water and dilute acid pretreatment allows selective solubility of hemicellulose which improves the accessibility of enzymes for cellulose hydrolysis. The highest yield of TRS was observed at run order 8 for both acid and hot water pretreatment (23.49 and 26.50 gL^-1) with respect to sugarcane bagasse. But, the pretreatment results obtained for bamboo was slightly different to that of sugarcane bagasse. The highest yield of TRS was obtained at run order 8 for acid (15.6 gL^-1) and run order 10 for hot water (17.98 gL^-1) pretreatment respectively. Irrespective of biomass type, hot water pretreatment process produced more TRS than acid pretreatment process.