Chapter 6 Figure 6.3.1
1.2 Aim and scope of present thesis
all Indian states. Due to this feature, the cost of production of ethanol with lignocellulosic substrate is expected to be much lower than the molasses based ethanol.
Before the new technology for ethanol production from lignocellulosic biomass is implemented commercially, significant research and development is required to meet the set of challenges and opportunities associated with it. It is in this spirit that the current thesis work is planned and implemented. The present thesis has attempted to develop, optimize and intensify a laboratory scale process for bioethanol production from waste biomass of Parthenium hysterophorus. All aspects of the process, starting from acid pretreatment, alkaline delignification, enzymatic hydrolysis and fermentation of both pentose (acid) and hexose (enzyme) hydrolyzate have been addressed in stepwise manner. Thus, this thesis can also be looked at as a laboratory scale technology package for bioethanol production from Parthenium hysterophorus. P. hysterophorus is a noxious weed found abundantly in India. This weed has not only destroyed arable land causing loss of billions of rupees, but has also posed potential health hazard to humans and animals. The process developed in this thesis thus also provides solution to a potential environmental problem.
processes. In addition, intensification of various processes involved in above mentioned steps have also been done by applying ultrasound. The work in the thesis has been presented by the following chapters:
Chapter 2 is a comprehensive review of literature focused on bioethanol production from lignocellulosic biomass. This chapter involves the review of the studies considering following major aspects of cellulosic ethanol production:
(a) Enzymatic hydrolysis of cellulosic biomass: The main components of the enzymatic hydrolysis of lignocellulosic biomass are the cellulase and pretreated biomass (rich in cellulose). Also the economy of ethanol production depends more on the potential of these two components. Therefore, in foremost part of the chapter the focus was on the review of the reports on natural sources and efficient production of cellulase, followed by purification, characterization and major applications of the enzyme.
(b) Pretreatment of lignocellulosic biomass: The subsequent focus of the chapter was on the review of the reports on various types of lignocellulosic feedstock and the methods of pretreatment/delignification of the biomass.
(c) Fermentation for ethanol production: The chapter was preceded with the review of the literature on the various attributes on the different modes of ethanol fermentation.
(d) Intensification of the bioprocesses by ultrasound: Since the present thesis focused equally on the intensification of the processes involved in bioethanol production, a major part of this chapter included the review of the investigations in the area of ultrasound-assisted enzymatic hydrolysis and fermentation. The
chapter also included the review of the reports on mechanistic investigations of the effect of sonication on various bioprocesses using various mathematical models.
Chapter 3 deals with the isolation, screening, identification and characterization of cellulolytic bacteria from rhinoceros dung. The isolate, exhibiting maximum CMCase activity, was identified as Bacillus amyloliquefaciens SS35 by morphological, biochemical and phylogenetic analyses.
Chapter 4 describes the statistical optimization of CMCase production from B.
amyloliquefaciens SS35. The statistical experimental designs were applied in two steps viz. medium optimization and optimization of fermentation parameters.
Plackett-Burman design followed by Central Composite Design (CCD) was used for medium optimization, while for optimization of fermentation parameters one- variable-at-a-time method followed by central composite design was used.
Chapter 5 deals with the purification and characterization of CMCase from B.
amyloliquefaciens SS35. Purification was done by ammonium sulphate fractionation method and anion exchange chromatography using DEAE-Sepharose. Molecular weight of the enzyme was determined by SDS-PAGE and zymogram analysis.
Effects of physical parameters and additives on enzyme activity and stability were also investigated.
Chapter 6 describes the comparative assessment of pretreatment strategies and optimization of ultrasound-assisted alkaline delignification for P. hysterophorus biomass. Various physical, chemical and physicochemical methods have been employed for the pretreatment with aim of exposure of cellulose moieties in biomass
for enzymatic action during hydrolysis. In addition, the mechanistic insight into ultrasound assisted delignification of P. hysterophorus biomass has also been attempted in this chapter.
Chapter 7 deals with the investigations on separate enzymatic hydrolysis of P.
hysterophorus biomass and subsequent fermentation of hydrolysate. The optimization of hydrolysis process was carried out by response surface methodology (RSM). The efficiency (in terms of yield and kinetics) of conventional hydrolysis and fermentation processes was improved by employing intermittent ultrasonic irradiation. The influence of ultrasound on rate of hydrolysis was investigated by fitting the data to Michaelis-Menten kinetic model. The effect of sonication on fermentation parameters was investigated by fitting the experimental data to a mathematical model.
Chapter 8 deals with the simultaneous saccharification and fermentation (SSF) of pretreated and delignified P. hysterophorus biomass. The effect of ultrasonic irradiation on SSF process was also investigated by fitting the experimental data to the saccharification/ fermentation model.
Chapter 9 represents the summary of results and overall conclusion of the thesis. Some suggestions have been made for taking the thesis work ahead.
References
Biomass Resource Atlas of India, Indian Institute of Science Bangalore, India.
Global Agricultural Information Network (GAIN) report (2014), number: IN4055.
Indian Petroleum and Natural Gas Statistics (2014) Government of India, Ministry of Petroleum and Natural Gas Economics and Statistics Division, New Delhi.
Key World Energy Statistics (2014) International Energy Agency, Paris, France.
Technology Road Map: Biofuels for Transport (2011) IEA Renewable Energy Division, International Energy Agency,Paris, France.
Chapter 2
Literature survey on lignocellulosic wastes to ethanol: process development, optimization and intensification