2.8.3 Production Process
Butanol is produced through a unique fermentation process called as acetonebutanol-ethanol (ABE) fermentation. ABE fermentation pathway is the typical
feature of the genus Clostridium and certain strains involved in butanol production
by this pathway are Clostridium acetobutylicum (Weizmann’s organism), Clostridium saccharoperbutylacetonicum and Clostridium beijerinckii. Clostridium sp. is a
rod-shaped organism with anaerobic growth capable of forming heat-resistant endospores and having G+ type of bacterial cell wall. During fermentation three major
products are formed viz., acetone, butanol and ethanol are produced in 3:6:1 ratio
(Green 2011; Pugazhendhi et al. 2019).
2.8.4 Pretreatment Process
Pretreatment is an important step before the fermentation. Pretreatment converts
cellulose to glucose and various other sugars which is ultimately utilized during the
fermentation and govern the fermentation efficiency.
First-generation feedstock generally employs simple pretreatment of biomass as
this feedstock has high concentration of sugar and also this is easily accessible. Acid
treatment, heat sterilization and deproteinization can be used to treat first-generation
feedstock.
Second-generation feedstock is more complex as compared to others as they have
high amount of lignin, cellulose and hemicellulose which requires comprehensive
pretreatment so as to release the sugars for the fermentation process.
Third-generation biomass is less complex and is a good substrate for biobutanol
production.
2.8.5 Physical Treatment
Physical methods employed for pretreatment are milling such as wet milling and dry
milling, microwave, pyrolysis, etc. The main objective of physical method is to
reduce the particle size of the feedstock which ultimately leads to increase in the
surface area. Increase in surface area further increases the efficiency of the process;
however, the disadvantage of the physical methods is that it is a high energy
consuming process.
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N. Jaiswal et al.
Butanol is produced through a unique fermentation process called as acetonebutanol-ethanol (ABE) fermentation. ABE fermentation pathway is the typical
feature of the genus Clostridium and certain strains involved in butanol production
by this pathway are Clostridium acetobutylicum (Weizmann’s organism), Clostridium saccharoperbutylacetonicum and Clostridium beijerinckii. Clostridium sp. is a
rod-shaped organism with anaerobic growth capable of forming heat-resistant endospores and having G+ type of bacterial cell wall. During fermentation three major
products are formed viz., acetone, butanol and ethanol are produced in 3:6:1 ratio
(Green 2011; Pugazhendhi et al. 2019).
2.8.4 Pretreatment Process
Pretreatment is an important step before the fermentation. Pretreatment converts
cellulose to glucose and various other sugars which is ultimately utilized during the
fermentation and govern the fermentation efficiency.
First-generation feedstock generally employs simple pretreatment of biomass as
this feedstock has high concentration of sugar and also this is easily accessible. Acid
treatment, heat sterilization and deproteinization can be used to treat first-generation
feedstock.
Second-generation feedstock is more complex as compared to others as they have
high amount of lignin, cellulose and hemicellulose which requires comprehensive
pretreatment so as to release the sugars for the fermentation process.
Third-generation biomass is less complex and is a good substrate for biobutanol
production.
2.8.5 Physical Treatment
Physical methods employed for pretreatment are milling such as wet milling and dry
milling, microwave, pyrolysis, etc. The main objective of physical method is to
reduce the particle size of the feedstock which ultimately leads to increase in the
surface area. Increase in surface area further increases the efficiency of the process;
however, the disadvantage of the physical methods is that it is a high energy
consuming process.
62
N. Jaiswal et al.