Utilization of sugarcane juice and bagasse for bioethanol production
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Date
2022
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Punjab Agricultural University, Ludhiana
Abstract
The present study was carried out to optimize the process for bioethanol production from sugarcane juice and bagasse. The juice and bagasse of 29 sugarcane varieties/clones belonging to different
maturity groups (early and mid-late) was evaluated for various biochemical parameters. Among all varieties/clones, high holocellulose (69.75%) and cellulose (39.55%) along with low lignin (20.05%) and ash content (1.80%) was observed in the bagasse of sugarcane variety CoPb 92. The juice of this variety also contained high total sugars (19.09 g 100ml-1) and sucrose content (18.55 g 100ml-1). On the basis of desirable chemical components of the bagasse and juice, sugarcane variety CoPb 92 was identified to be the most suitable for ethanol production and selected for further studies. Bagasse of sugarcane variety CoPb 92 was subjected to different chemical pre-treatments, out of which alkali pre-treatment, i.e. 1 M sodium hydroxide for 60 min (T15) was found to be the effective in decreasing the lignin content of bagasse along with high recovery of holocellulose and cellulose content. A total of 17 fungi were isolated for cellulase production and their cellulolytic index ranged from 0.12 to 0.94. Quantitative cellulase production by five fungal isolates showing high cellulolytic index under liquid shake flask fermentation was carried out. Significantly high carboxymethyl cellulase (171.98 U l-1), cellobiase (78.65 U l-1), filter paper activities (43.52 U l-1) and extracellular protein content (422.34 mg l-1) was recorded for the fungal isolate JS17. Sequencing and analysis of the internal transcribed spacer (ITS) region of the isolated fungal strain JS17 revealed that these regions had the highest identity (100%) with Penicillium mallochii. Endoglucanase enzyme was purified and three isoforms, i.e. EG-I, EG-II and EG-III were identified with molecular weight of 23.4, 24.5 and 19.9 kDa, respectively. The enzymatic saccharification of alkali pre-treated sugarcane bagasse with inhouse cellulase from P. mallochii resulted in the maximum reducing sugar content of 651.60 mg g-1 with hydrolytic efficiency of 78.29 per cent. The maximum ethanol concentration of 67.90 g l-1 was obtained from the sugarcane juice (CoPb 92) fermented by yeast S. cerevisiae NCIM3078 at 96 h of fermentation. Significantly high ethanol concentration of 9.55 g l-1 was recorded from the sugarcane bagasse saccharified with in-house cellulase produced from P. mallochii. The present study, thus, revealed that sugarcane in terms of juice and bagasse could be ideally used as a substrate for bioethanol production using the optimized pre-treatment, hydrolysis and fermentation parameters.
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Jaspreet Kaur (2022). Utilization of sugarcane juice and bagasse for bioethanol production (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.