Experimental investigation of a sequential process for the fractionation of sweet sorghum bagasse

Sweet sorghum bagasse (SSB) was fractionated into hemicellulosic sugars and cellulose-rich residue in a two-step process using water and calcium hydroxide. The optimum conditions for autohydrolysis of SSB using water at 121 °C were 13 %(g/g) substrate and 90 min isothermal treatment time that could extract 72.69 ± 0.08 % (g/g) of the hemicellulose from the substrate. The calcium hydroxide treatment of the autohydrolysed SSB under optimum conditions at 121 °C, 10 % (g/g mixture) substrate loading, Ca(OH)₂ at 10 % (g/g of substrate) and 106 min isothermal treatment could extract 69.67 ± 1.26 % (g/g) of the lignin from the substrate into a yellow liquor. The lignin was isolated from the yellow liquor by using CO₂ at room temperature. Adding CO₂ at a flow rate of 17 mL/min precipitated 65.99 ± 1.2 % (g/g) of the calcium hydroxide as calcium carbonate and 58.85 ± 3.2 % (g/g) of the lignin in the yellow liquor at room temperature. The FTIR, DSC and SEM analyses confirmed the compositional and morphological changes in the treated SSB samples.