**Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products**

Larissa Canilha, Rita de Cássia Lacerda Brambilla Rodrigues, Felipe Antônio Fernandes Antunes, Anuj Kumar Chandel, Thais Suzane dos Santos Milessi, Maria das Graças Almeida Felipe and Silvio Silvério da Silva

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53832

**1. Introduction**

Hydrolysis of Miscanthus sinensis to Monosaccharides Biosci. Biotechnol. Biochem.,

[29] Kumar P, Barrett DM, Delwiche MJ, Stroeve P. Methods for Pretreatment of Ligno‐ cellulosic Biomass for Efficient Hydrolysis and Biofuel Production. Ind. Eng. Chem.

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

2008, 72: 805-810.

Res., Article ASAP.DOI: 10.1021/ie801542g.

Sugarcane is main crop cultivated in countries like Brazil, India, China, etc. It plays a vital role in the economy of these countries in addition to providing employment opportunities [1]. Only in the 2012/13 Brazil harvest, for example, it was estimated that more than 602 mil‐ lion tons of sugarcane will be processed by the sugar-alcohol mills [2].

During the processing of sugarcane, the sugarcane straw (SS) is remained on field and do not presents suitable use. After the juice extraction from sugarcane stem, the fraction that is left over is called sugarcane bagasse (SB) [3]. Both residues (SB and SS) represent a sizeable fraction of agro-residues collected annually. The annual world production of sugarcane is ∼1.6 billion tons, which yields approximately 279 million metric tons (MMT) of SB and SS [1, 4].

SB is used as a source of heat and electricity in sugar producing mills while SL is open‐ ly burnt on the fields causing environmental pollution. The harnessing of both residues via biotechnological routes into value-added products (xylitol, organic acid, industrial en‐ zymes, ethanol, etc) is much more likely to be complimentary than competitive in the near term without jeopardizing the food requirements [5, 6, 7]. Both residues (SB and SS)

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 production) [8, 9, 12].

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

(a)

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

http://dx.doi.org/10.5772/53832

17

(b)

(c)

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

unpublished work).

some vacuoles in the structure, which is not common in SB (Figure 1C).

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‐ ars into sustainable products.
