Paddy straw is one of the abundant lignocellulosic waste materials in the world and have the potential to produce about 120,000 million liters of fuel ethanol. India is one of the world's largest producers of white rice and brown rice, accounting for 20% of all world rice production. About 100-110 million tons of paddy straw is generated every year in India, which is a potential feedstock for fuel ethanol production as it has high cellulose and hemicelluloses content that can be readily hydrolyzed into fermentable sugars. In terms of chemical composition, the straw predominantly contains cellulose (32-47%), hemicellulose (19-27%) and lignin (5-24%). High temperature pretreatments, such as auto-hydrolysis or hydrothermal showed the capacity to break hydrogen bonds between the cellulose fibers, ester and ether bond between cellulose-lignin, hemicellulose-lignin and Lignin-lignin. Also, application of chemicals is not required which reduce the chances of generation of inhibitors. Now a day's application of glycerol in the field of pretreatment of lignocellulose was increased as its high thermal capacity, high boiling point (290 ºC) with extreme stability at high temperature. Therefore, in the present investigation on application of hydrothermal and glycerol for pretreatment of paddy straw has been focused. The effect of pretreatment was assessed on the basis of reducing sugar yield, enzyme kinetics and enzyme adsorption study, ultrastructural and chemical changes with mass balance and energy balance.
The GTP pretreatment showed four times more RS yield than that of untreated biomass and two-fold increase over hydrothermal pretreatment. Defibrillation of cellulose fiber was observed in GTP pretreatment, however, complete collapse of paddy straw was observed in hydrothermal pretreatment. Enzyme adsorption was nearly two-fold on GTP pretreated paddy straw than hydrothermal pretreated straw. Enzyme kinetic clearly showed hydrolysis of cellulose in GTP at faster rate than hydrothermal pretreatment. A study on FTIR clearly shows more degradation of lignin associated group in GTP than hydrothermal pretreatment. Present investigation shows that the glycerol thermal pretreatment (GTP) is an effective mean of pretreatment of paddy straw. Considering the glycerol as by-product of bio-diesel industry it can be concluded GTP is a potential and economical pretreatment strategy for biofuel production. However, further works are contemplated at higher scales.
|
