materials are available in large quantities and their products are all over our daily
lives (Kamm and Kamm 2007). For instance, the 2018/2019 Brazilian sugarcane
harvest was estimated at 615.84 million tons (CONAB 2018). The annual production
of lignocellulosic material around the world hovers from 10 to 50 billion tons,
representing 50% of the biomass materials on Earth (Zhao et al. 2012).
Lignocellulosic biomasses are organized into different categories based on
their sources, which include crops destined to energy generation, aquatic plants,
forest biomass and wastes, agricultural, and organic materials obtained from solid
waste (Limayem and Ricke 2012). The lignocellulosic materials possess large
quantities of carbohydrates, reaching more than 70% of its weight. These
carbohydrates are an important source of sugar for biofuel generation and biodegradable products (Jørgensen et al. 2007). Unfortunately, the highly organized and
resistant framework present in these materials results in protection from biological
and chemical processes, a phenomenon called recalcitrance (Zhao et al. 2012).
Recalcitrance is associated with the physicochemical characteristics of the plant
cell walls. The presence of hemicellulose and lignin in the cell structure builds
natural barriers that protect cellulose from hydrolysis or chemical aggression,
maintaining its structure. Besides lignin and hemicelluloses, other factors affect
biomass recalcitrance, such as physicochemical properties of the cellulose.
Several physical, chemical, biological, and combination of these pretreatments
have been studied with the goal of enhancing the access to lignocellulosic biomass
compounds, eliminating/modifying hemicelluloses and lignin, diminishing the cellulose crystallinity, improving cellulose accessibility and porosity, minimizing the
sugars loss, and limiting the inhibitor formation (Kumar and Sharma 2017). Genetic
modifications of the plant cell wall are being studied to alter the wall component
interconnections and cellulose crystallinity, reducing lignin levels and increasing
carbohydrate content.
RESIDUE
BIOMASS
HEMICELLULOSE
XILOSE
CELULOSE
GLUCOSE
VEGETABLE
BIOMASS
FRUCTOSE
SOURCES
SUCROSE
SOURCES
STARCH
SOURCES
BIOETANOL
Fig. 2.1 Bioethanol production from carbohydrate sources of biomass
38
F. L. Shimizu et al.
lives (Kamm and Kamm 2007). For instance, the 2018/2019 Brazilian sugarcane
harvest was estimated at 615.84 million tons (CONAB 2018). The annual production
of lignocellulosic material around the world hovers from 10 to 50 billion tons,
representing 50% of the biomass materials on Earth (Zhao et al. 2012).
Lignocellulosic biomasses are organized into different categories based on
their sources, which include crops destined to energy generation, aquatic plants,
forest biomass and wastes, agricultural, and organic materials obtained from solid
waste (Limayem and Ricke 2012). The lignocellulosic materials possess large
quantities of carbohydrates, reaching more than 70% of its weight. These
carbohydrates are an important source of sugar for biofuel generation and biodegradable products (Jørgensen et al. 2007). Unfortunately, the highly organized and
resistant framework present in these materials results in protection from biological
and chemical processes, a phenomenon called recalcitrance (Zhao et al. 2012).
Recalcitrance is associated with the physicochemical characteristics of the plant
cell walls. The presence of hemicellulose and lignin in the cell structure builds
natural barriers that protect cellulose from hydrolysis or chemical aggression,
maintaining its structure. Besides lignin and hemicelluloses, other factors affect
biomass recalcitrance, such as physicochemical properties of the cellulose.
Several physical, chemical, biological, and combination of these pretreatments
have been studied with the goal of enhancing the access to lignocellulosic biomass
compounds, eliminating/modifying hemicelluloses and lignin, diminishing the cellulose crystallinity, improving cellulose accessibility and porosity, minimizing the
sugars loss, and limiting the inhibitor formation (Kumar and Sharma 2017). Genetic
modifications of the plant cell wall are being studied to alter the wall component
interconnections and cellulose crystallinity, reducing lignin levels and increasing
carbohydrate content.
RESIDUE
BIOMASS
HEMICELLULOSE
XILOSE
CELULOSE
GLUCOSE
VEGETABLE
BIOMASS
FRUCTOSE
SOURCES
SUCROSE
SOURCES
STARCH
SOURCES
BIOETANOL
Fig. 2.1 Bioethanol production from carbohydrate sources of biomass
38
F. L. Shimizu et al.