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Integrated Production of Ethanol from Starch and Sucrose
Published in Ayerim Y. Hernández Almanza, Nagamani Balagurusamy, Héctor Ruiz Leza, Cristóbal N. Aguilar, Bioethanol, 2023
C. A. Prado, S. Sánchez-Muñoz, R. T. Terán-Hilares, L. T. Carvalho, L. G. De Arruda, M. L. Silva da Cunha, P. Abdeshahian, S. S. Da Silva, N. Balagurusamy, J. C. Santos
After the pretreatment, it is necessary to convert the polymeric carbohydrate obtained from lignocellulosic material into fermentable sugars (Figure 10.3), due to the yeast inability to process carbohydrate polymers [217]. Therefore, two hydrolysis methods can be applied in order to provide second-generation bioethanol production, including acid and enzymatic hydrolysis, which are chosen according to the biomass composition [67]. Acid hydrolysis can be performed by dilute acid or concentrated acid with demanding different temperature and pressure conditions [17]. Sulfuric acid (H2SO4) [80] is mostly applied for acid hydrolysis, however, researchers have also developed different methods, including hydrochloric acid (HCl), nitric acid (HNO3), and phosphoric acid (H3PO4) [81]. Enzymes can also be used to hydrolyze both cellulose and hemicellulose components, in order to produce fermentable sugars. Enzymatic hydrolysis (enzymatic saccharification) has high advantages such as the requirement of mild process conditions (low temperature and atmospheric pressure) with avoiding acid corrosion [17, 82]. This type of hydrolysis enhances the soluble sugar production by cellulase, xylanase or amylase [82]. In order to reduce the cost of 2G bioethanol and make it large scale commercialization, it is necessary to improve the process economics, for example, by decrease in the cost of cellulase production and enzymatic hydrolysis [83].
Third-Generation Biofuels: An Overview
Published in Arindam Kuila, Sustainable Biofuel and Biomass, 2019
João Moreira Neto, Andrea Komesu, Luiza Helena Da Silva Martins, Vinicius O.O. Gonçalves, Johnatt Allan Rocha De Oliveira, Mahendra Rai
In acid hydrolysis, a wide range of acids has been used in which sulfuric acid (H2SO4) is the most preferred. It has been found that the polysaccharides of the three classes of macroalgae (brown, red, and green) can be effectively hydrolyzed to monosaccharides by treatment with H2SO4 diluted at high temperature. The acidic role in the hydrolysis can be seen in its ability to break the bonds of long chains of polysaccharides. In the initial stage, the destruction of hydrogen bonds occurs to break up the chains of polysaccharides transforming them into molecules in the amorphous state. Polysaccharides are extremely susceptible to acid hydrolysis at this point. The acid will then serve as the catalyst where the cleavage of the polysaccharide will occur by the hydrolysis of the glycosidic bonds. At the end of the process, any addition or dilution with water at moderate temperature will provide complete hydrolysis and the hydrolyzate will be rich in monosaccharides (Jambo et al., 2016).
Enzymatic technologies of chitin and chitosan
Published in Antonio Trincone, Enzymatic Technologies for Marine Polysaccharides, 2019
Current trends in the field of chitin research have focused on oligosaccharides/oligomers and monomers, which are more soluble and have several attractive biological effects (Feisal and Montarop 2010; Kumar and Suresh 2014). Water-soluble LMW N-acetyl-COS can be prepared by depolymerization of the polymer chains. For some specific applications, these derivatives have been found to be much more valuable specifically in food and biomedicine. Chitin depolymerization can be carried out both chemically and enzymatically. Their degree of polymerization (DP) is usually <20. Chemical depolymerization is carried out primarily by hydrolysis of chitin using concentrated mineral acid (HCl or H2SO4) at different process conditions and time. The acid hydrolysis has the disadvantages of low yield, the formation of acid waste, high production cost, deacetylation of products, and a significant amount of monomeric GlcNAc (Sashiwa et al. 2003; Binod et al. 2007; Suresh and Kumar 2012; Thadathil et al. 2014). Therefore, enzymatic hydrolysis of chitin is attracting increasing interest for applications requiring mild reaction conditions, to control the extent of hydrolysis and product consistency (Sashiwa et al. 2003; Ilankovan et al. 2006; Binod et al. 2007). The enzymatic depolymerization of chitin to LMW soluble derivatives is carried out by the chitinolytic enzyme system.
Anaerobic detoxification fermentation by Rhodospirillum rubrum for rice straw as feed with moderate pretreatment
Published in Preparative Biochemistry and Biotechnology, 2018
Jian Zhang, Jie Yuan, Wen-Xue Zhang, Fang Tu, Ya Jiang, Chuan-Ze Sun
Acid hydrolysis is commonly used to pretreat lignocellulosic material for use in fermentation. Concentrated acid hydrolysis can achieve high cellulose degradation,[32] but requirements for expensive equipment and separation of the acid from the hydrolysate are key obstacles for application of the concentrated acid approach (neutralization also produces problematic byproducts). To improve the degradation of cellulose, dilute acid hydrolysis is usually performed at high temperatures and pressures,[24] increasing the difficulty and cost of the process and the toxic materials contents, including furfural, 5-HMF, acetic acid, phenols, etc.[33] High concentration of toxic materials can be harmful to some species.[33,34] Therefore, in this study, dilute acid hydrolysis was performed at an easily achievable 100°C and atmospheric pressure to decrease the difficulties associated with other methods, and not to be optimized in advance.
Bioethanol production from rice hull and evaluation of the final solid residue
Published in Chemical Engineering Communications, 2018
Christiano de C. Lamb, Bruna Martini Zacarias da Silva, Diego de Souza, Franccesca Fornasier, Larissa Brixner Riça, Rosana de Cassia de Souza Schneider
To perform the cellulose saccharification, it is necessary to pretreat the biomass. The acid pretreatment removes and/or modifies hemicellulose and lignin, increasing the surface area, decreasing the degree of polymerization and crystallinity of the cellulose, exposing the cellulose for conversion, and facilitating the enzymatic hydrolysis (Mosier et al., 2005). Among the pretreatment, acid hydrolysis is highlighted once it can be performed at high temperatures or under mild conditions (Table 1). Acid hydrolysis is performed with different types of acids, being H2SO4 the most used.
Purification of chitosanases produced by Bacillus toyonensis CCT 7899 and functional oligosaccharides production
Published in Preparative Biochemistry & Biotechnology, 2022
Julia Maria de Medeiros Dantas, Nathália Kelly de Araújo, Nayara Sousa da Silva, Manoela Torres-Rêgo, Allanny Alves Furtado, Cristiane Fernandes de Assis, Renata Mendonça Araújo, José António Teixeira, Leandro de Santis Ferreira, Matheus de Freitas Fernandes-Pedrosa, Everaldo Silvino dos Santos
Production of chitosan oligosaccharides or chitooligosaccharides (COS) can occur via acid or enzymatic hydrolysis. Acid hydrolysis has several drawbacks such as the complexity of reaction control, high energy consumption and by-products formation.[1] On the other hand, enzymes have high specificity when compared with acid techniques, and the product profile is easy to manipulate by changing reaction conditions as time, pH and temperature, so this method might be more suitable for COS production.[2–4]