**2. Sugarcane, bagasse and straw**

#### **2.1. Structure of sugarcane**

The sugarcane basically consists of stem and straw. Stem is the part normally associated with sugarcane (cleaned cane). It is the piece of cane plant between plantation level and end node from last stem. The sugarcane stem are crushed to obtain cane juice, which is subsequently used for sugar (sucrose) or alcohol (ethanol) production. Sugarcane bagasse (SB) is the left over residue from stems after extraction of juice. It is normally burned to supply all the energy re‐ quired in the process [13]. Sugarcane straw (or trash) (SS) is composed by fresh leaves, dry leaves and tops available before harvesting. Fresh (green and yellow) leaves and tops are the part of cane plant between the top end and the last stalk node. Dry leaves are normally in brownish color [14]. The SS is also normally burnt in the field after the harvest of the crop [15]. Potential applications of the leaves include: 1) as a fuel for direct combustion; 2) as a raw mate‐ rial for conversion by pyrolysis to char, oil and/or gas; and 3) as a raw material for conversion by gasification and synthesis to methanol. Potential applications of the tops include: 1) as a ru‐ minant feed, either fresh or dried; 2) as a substrate for anaerobic fermentation to methane pro‐ duction; and 3) after reduction in water content, for the three energy uses listed for cane trash. Figure 1 presents the scanning electronic microscopy (SEM) of SS and SB before pretreatment. In the Figures 1A and 1B the SS was amplified 500 and 10.000x which reveal the presence of some vacuoles in the structure, which is not common in SB (Figure 1C).

are principally constituted of cellulose, hemicellulose and lignin. Among these constitu‐ ents, hemicellulose is of particular interest because of its unique properties and composi‐ tion. In the last two decades of research has been witnessed the technological development for the hemicellulose depolymerization into its monomeric constituents, mainly xylose, and their subsequent conversion into value-added products via microbial fermentation [8, 9, 10]. Dilute acid hydrolysis is a well established process for hemicellu‐ lose depolymerization, however, inhibitory compounds of microbial metabolism are also formed and should be reduced/eliminated prior to using the liquid in the fermentation process [8, 9]. On the other hand, enzymatic conversion of hemicellulose, that requires cocktail of enzymes for its breakdown, is slow, costly and requires combinatorial mixture of specialized enzymes [9]. The recovered sugar solution after hemicellulose hydrolysis contains primarily pentose sugars and the fermentation of these pentosans is problemat‐ ic. Only limited numbers of microorganisms that use pentose are known and the fermen‐ tation of pentose sugars at industrial scale is not established yet [10, 11]. Generally, pentose utilizing microorganisms have slow growth rate, low osmotolerance and have poor resistance against inhibitors. The microorganisms that use pentose more extensively explored in laboratories are *Candida shehatae*, *Pichia stipitis*, *Pachysolen tannophilus* (for ethanol production), *C. utilis, C. intermedia*, *C. guilliermondii (*for xylitol production) and *Klebsiella oxytoca* ATCC 8724, *Bacillus subtilis*, *Aeromonas hydrophilia* (for 2, 3-butanediol

16 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

Rather than summarizing all the literature on hemicellulose bioconversion from sugarcane agro-residues, we aim to highlight in this chapter technological developments focusing hemicellulose hydrolysis, detoxification of hydrolysates and microbial fermentation of sug‐

The sugarcane basically consists of stem and straw. Stem is the part normally associated with sugarcane (cleaned cane). It is the piece of cane plant between plantation level and end node from last stem. The sugarcane stem are crushed to obtain cane juice, which is subsequently used for sugar (sucrose) or alcohol (ethanol) production. Sugarcane bagasse (SB) is the left over residue from stems after extraction of juice. It is normally burned to supply all the energy re‐ quired in the process [13]. Sugarcane straw (or trash) (SS) is composed by fresh leaves, dry leaves and tops available before harvesting. Fresh (green and yellow) leaves and tops are the part of cane plant between the top end and the last stalk node. Dry leaves are normally in brownish color [14]. The SS is also normally burnt in the field after the harvest of the crop [15]. Potential applications of the leaves include: 1) as a fuel for direct combustion; 2) as a raw mate‐ rial for conversion by pyrolysis to char, oil and/or gas; and 3) as a raw material for conversion by gasification and synthesis to methanol. Potential applications of the tops include: 1) as a ru‐ minant feed, either fresh or dried; 2) as a substrate for anaerobic fermentation to methane pro‐

production) [8, 9, 12].

ars into sustainable products.

**2.1. Structure of sugarcane**

**2. Sugarcane, bagasse and straw**

**Figure 1.** SEM of sugarcane straw (A) 500x and (B) 1000x [16] and sugarcane bagasse (C) 500x (Chandel et al., unpublished work).
