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220                     Refining Biomass Residues for Sustainable Energy and Bioproducts


         sorghum (MMT), area harvested (M ha), total supply (MMT), food, seed and indus-
         trial (FSI) consumption (MMT), domestic consumption (MMT), and domestic feed
         consumption (MMT) from 1960 to 2018. In recent times, a fast and amplified rec-
         ognition is found for sorghum near coastal Andhra Pradesh (Chapke et al., 2011,
         2016). Sorghum can be cultivated in semiarid tropical regions in a highly effective
         manner, whereas there is a miserable growth in the case of other food crops and
         best suited in dry land cultivation area also. Sorghum can be cultivated 2 3 times
         in a year effectively as it attains maturity within 4 months and it is tolerant to tem-
         perature, salinity, and water stress and can also be grown as a rain-fed crop (Yin
         et al., 2013). Sorghum grow at temperature between 32 C and 34 C, is considered


         as optimum for its growth and photosynthesis, and can also grow within the temper-
         ature range of 12 C 37 C.


         10.2.3 Composition
         Compositional analysis shows that sweet sorghum contains major components such
         as lignin and both insoluble (cellulose and hemicellulose) and soluble (glucose and
         sucrose) carbohydrates, while its bagasse cellulose, hemicellulose, and lignin con-
         tent are 26.3%, 20.0%, and 10.1%, respectively. The composition varies with differ-
         ent varieties, type of soil, and ecological conditions. Sorghum biomass constituents
         are depicted in Fig. 10.3.


         10.2.3.1 Lignin

         Lignin is considered the most abundant aromatic and amorphous three-dimensional
         phenolic biopolymer. Lignin biosynthesis arises from the polymerization of three
         different types of monolignols: (1) p-coumaryl alcohol, (2) sinapyl alcohol, and (3)
         coniferyl alcohol responsible for the firm structure. Respective monolignols synthe-
         size the lignin units, that is, p-hydroxyphenyl (H), syringyl (S), and guaiacyl (G)
         (Sen et al., 2015). Sweet sorghum, forage sorghum, and PS sorghum comprise
         10.1%, 10.6%, and 10.4% of total lignin, respectively (Staggenborg, 2016).


         10.2.3.2 Cellulose
         Cellulose consists of glucose units, which are anhydrous in homopolysaccharide
         chain attached by β(1,4)-glycosidic bonds. The presence of inter and intramolecular
         hydrogen bonds helps cellulose to have a crystalline structure and also enables the
         fibril aggregation. A cellulose unit is generally identified as elementary fibril that
         assembles microfibrils formation. Hemicellulose matrices are generally cross-linked
         by the microfibril, forming the macro-fibrils, and acts as a barrier to chemical and
         enzymatic attacks (Gollakota et al., 2018; Kannam et al., 2017). Sweet sorghum,
         forage sorghum, and PS sorghum mainly contain 26.3%, 29.5%, and 29.3% of cel-
         lulose, respectively (Staggenborg, 2016).
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