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Subject: Biochemistry × Author: Jaspreet Kaur × End date: 2017 × Start date: 2010 ×
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    ThesisItemOpen Access
    Microwave and chemical assisted pretreatment of rice straw for bioethanol production
    (Punjab Agricultural University, Ludhiana, 2016) Jaspreet Kaur; Taggar, Monica Sachdeva
    The present study was carried out to develop a process for bioethanol production using microwave chemical pretreatment of rice straw. The comparative studies on different pre-treatment methods of rice straw viz. microwave acid and microwave alkali (at 480 W for 10 min), acid autoclave (for 30 and 90 min) and alkali autoclave (for 30 and 90 min), revealed that acid autoclave pre-treatment (90 min) recorded significantly lowest mean hemicellulose content of 7.53 per cent and microwave alkali pre-treatment (480 W-10 min) recorded significantly lowest mean lignin content of 4.36 per cent. Significantly highest mean cellulose content of 44.56 per cent was recorded in acid autoclave pre-treatment for 90 min. Based on these studies, a two step pre-treatment process involving acid autoclave pre-treatment, followed by microwave alkali pre-treatment for the removal of hemicellulose and lignin, respectively was selected for further studies. The reaction conditions were optimized by using Response Surface Methodology. The optimized conditions for acid autoclave pre-treatment were observed to be 1.90 per cent acid concentration; 51.85 min time and 17.51 soild:liquid ratio. The maximum release of reducing sugars i.e., 16.94 g per 100 g straw and minimum release of furfurals i.e., 0.93 g per 100 g straw was observed under these conditions. The optimized conditions for microwave alkali pre-treatment were observed to be 3.75 per cent alkali concentration; 9.16 min time and 475W microwave power. The lignin content of 2.96 per cent was observed in treated straw under these conditions. Scanning electron microscopy revealed extensive damage of silicified waxy surface and the disruption of the cell wall structure of rice straw after two step pre-treatment process. The cellulase from A. niger was used for enzymatic saccharification of pre-treated rice straw and the reducing sugar content was recorded to be maximum (63.66%) at 72 h after incubation. The maximum ethanol content of 1.16 g and 0.48 g was produced by the fermentation of hydrolysate obtained from enzymatically saccharified and acid autoclave pre-treated rice straw at 120 h after incubation, respectively. A two-step pre-treatment process was thus, an efficient pre-treatment method for bioethanol production.