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Prospects of Utilization of Various Solid Agro Wastes for Making Value Added Products for Sustainable Development
Published in Gunjan Mukherjee, Sunny Dhiman, Waste Management, 2023
J. Sharon Mano Pappu, Sathyanarayana N. Gummadi
Xylose is present abundantly in nature and the production of xylitol from xylose has a substantial economic part and sustainable nature as it involves lignocellulose biomass. Agricultural waste has been extensively explored as possible feedstock for production of xylitol. The monomeric sugars (D-xylose) in fermentable form are released from biomass after subjected to pretreatment. LCB that has been evaluated for xylitol production and the corresponding operational conditions along with yield and productivity are tabulated in Table 3. Initial pretreatment or hydrolysis to release xylose from hemicellulose was carried majorly by dilute acids at elevated temperature. Compounds such as furfural, hydroxymethylfurfural, phenolic compounds and vanillin that are formed through hydrolysis can act as inhibitors for the further fermentation process. It is desirable to remove the toxic compounds in the hemicellulose hydrolysates or to employ microorganisms that are tolerant to inhibitors for the fermentation. Debaryomyces nepalensis NCYC 3413, yeast strain, utilizes C5 and C6 sugars effectively to produce industrially significant products, mainly ethanol and other sugar alcohols (Kumar and Gummadi 2011). D. nepalensis, being a halotolerant strain, can be adapted easily for the production of metabolites from LCB since pre-treatment of cellulosic biomass leads to the formation of inhibitory compounds (Klinke et al. 2004).
New Uses for Hemicellulose
Published in Jorge M.T.B. Varejão, Biomass, Bioproducts and Biofuels, 2022
The wide range of uses presented above makes obtaining xylitol a field of great research. With the increase in consumption follows demand and the increase in the world population requires that a greater quantity be produced annually. Xylitol is chemically a polyol, showing its molecule an acyclic structure containing four asymmetric carbons. The synthetic approach to substances with several stereochemical centers is always difficult to succeed, due to the production of racemic mixtures that require separations of enantiomers, the most difficult to find. Consequently, xylitol must be obtained from biological sources that possess it or that are rich in xylose. Biomass contains approximately 30% dry weight of hemicellulose, a polymer in which xylose is the predominant monomer. Thus, a viable source for obtaining xylose is biomass, especially if it can be collected from accumulated residues by existing processing, such as cereal straw or residues from biomass processing, such as cellulose pulp preparation. Its separation and isolation can be problematic, but more recent results have shown better possibility.
Adsorption of Biologically Active Compounds on Mesoporous MOFs in Water
Published in Alexander Samokhvalov, Adsorption on Mesoporous Metal-Organic Frameworks in Solution for Clean Energy, Environment, and Healthcare, 2017
Xylose is a feedstock for production of furfural, which is further converted to furfuryl alcohol. The latter is used in the industrial-scale production of sustainable furan resins (Kandola et al. 2015). The separation and purification of the C5 and C6 sugars in aqueous solutions is of significant interest. Based upon the known interactions of boronic acids with sugars (Lü et al. 2013), the boronic acid residue –BO2H2 present in MOFs was assumed to function as a recognition unit for the adsorption of the cis–diol moieties in CDBs (Zhu et al. 2015). To synthesize boronic group–containing MIL-100-B, metallic Cr, 5-boronobenzene-1,3-dicarboxylic acid (BBDC), BTC, HF, and water were allowed to react in the autoclave. As representative CDBs, galactose, mannose, xylose, and glucose were chosen. At pH 6, the rather small amounts of CDBs were absorbed on MIL-100-B. The adsorbed amounts increased with the increase of the pH and at pH = 9 the adsorbed amount of galactose with the cis–diol group came to 95 mg/g, that is, 85% of the total amount. In the regeneration experiments under acidic conditions, >95% of galactose was desorbed from MIL-100-B in 0.1 M HNO3 at 25°C for 5 h. Upon regeneration of the “spent” MIL-100-B, the adsorption capacity decreased from 94.2 to 81.7 mg/g. The structure of MIL-100-B was preserved after three adsorption/desorption cycles as judged by XRD analysis (Zhu et al. 2015).
Process analysis for biphasic dehydration of xylose: effects of solvents on the purification of furfural
Published in Biofuels, 2021
Jiwon An, Geunjeong Lee, Jeong-Myeong Ha, Myung-June Park
Lignocellulose, including wood and plant matter, consists of three components: cellulose (40–50%), hemicellulose (20–30%), and lignin (20–25%) [6,8]. Xylose is a major pentose compound found in hardwood and grass and can be dehydrated to furfural in an acidic catalysis process [9]. A furfural yield of 39% is achieved at a moderate reaction temperature (418 K) in a single aqueous phase when a combination of Lewis and Brønsted acids is used, whereas the use of a single Brønsted acid (HCl) showed a 29% yield. With the combined catalyst functionalities, a much higher yield (76 mol%) of furfural can be obtained in a biphasic system, with low temperatures and short reaction times [10]. Sahu and Dhepe [6] compared the performance of various solvents for xylose dehydration, and an improvement in yield was observed for a biphasic system with toluene (solubility in water: 0.47 g/L at 20–25 °C), methyl isobutyl ketone (MIBK; solubility in water: 19.1 g/L at 20 °C), or p-xylene (solubility in water: 0.181 g/L at 20 °C) as the organic solvents, in comparison with the case with only water as a solvent. An unusually high temperature with a short contact time and an aqueous HCl catalyst was also suggested, achieving a high yield of 93.2% [11].
Optimization of xylitol production from xylose by a novel arabitol limited co-producing Barnettozyma populi NRRL Y-12728
Published in Preparative Biochemistry & Biotechnology, 2021
Badal C. Saha, Gregory J. Kennedy
Xylose is associated with the hemicellulose fraction of most lignocellulosic biomasses. Treatment with dilute acid at high temperature or hydrothermal pretreatment releases xylose as well as other hemicellulose sugars (e.g., glucose and arabinose) and inhibitory compounds such as acetic acid, furfural and HMF.[28–31] Time courses of xylitol production from xylose alone (50 g L−1) and in the presence of arabinose (7.5 g L−1), glucose (7.5 g L−1), acetic acid (6.0 g L−1), HMF (4 mM) and ethanol (2 g L−1) are presented in Figure 5A,B. The yeast strain produced 30.2 ± 0.4 g xylitol utilizing 46.8 ± 0.9 g xylose in 72 h with a xylitol yield of 0.65 g per g xylose consumed. Arabinose did not have an adverse effect on either xylose utilization or xylitol production. Only 1.4 g arabinose was utilized and 0.9 g arabitol was produced in 72 h per L by the yeast strain. The arabitol yield remained the same even after 135 h of fermentation. The xylitol purity was 97% in the culture broth. Glucose at the concentration used inhibited both xylose consumption and xylitol production by 49 and 54%, respectively as measured at 72 h. By 135 h, xylose consumption reached 46.4 ± 0.1 g and the xylitol titer was 18.6 ± 0.0 g L−1 (38% decrease from the control value). In comparison, glucose tested at 10 g L−1 inhibited xylitol production by 60% by C. peltata NRRL-6888.[24] In the presence of glucose, xylose consumption was severely repressed and diauxic sugar utilization was observed for C. tropicalis.[28]
Critical factors affecting ethanol production by immobilized Pichia stipitis using corn cob hemicellulosic hydrolysate
Published in Preparative Biochemistry and Biotechnology, 2018
Ethanol produced from lignocellulosic biomass is a potential renewable alternative fuel. Xylose is one of the major fractions of carbohydrate present in the lignocellulosic feedstock and it is necessary to ferment xylose to ethanol efficiently to make lignocelluloses to ethanol process economically viable.[1] Corn cob is a major waste obtained in corn production and also a promising and attractive feedstock for ethanol production. Corn cob hydrolysate contains both hexose and pentose sugars which can be converted into ethanol through fermentation process.[2]