Xylitol Yield Research Articles

Particle size influence on the composition of sugars in corncob hemicellulose hydrolysate for xylose fermentation by Meyerozyma caribbica

The xylitol production was performed with acidophilic Meyerozyma caribbica. The particle size of 0.02 ± 0.01 to 0.1 ± 0.05 mm was rich in glucose (12.0 ± 0.5 g/L), whereas 0.5 ± 0.25 to 2.0 ± 0.5 mm had a high content of xylose (8.0 ± 0.5 g/L). The xylitol production in the synthetic, non-detoxified and detoxified hydrolysate media was studied (50 ± 0.5 g/L) using 10% v/v non - induced cells of M. caribbica for 120 h. At the end of fermentation with the specific growth rate of 0.056 ± 0.01 (μ), xylitol yields of 45.00 ± 1.00%, 10.00 ± 1.00% and 54.00 ± 1.00% were obtained. The detoxification of the hydrolysate prepared using an identified corncob particle size of 0.5 ± 0.25 to 2.0 ± 0.5 mm could be used as the prospective pretreatment process for ecofriendly and industrial scale production of xylitol with M. caribbica.

Optimization of Xylose Reductase production from Citrobacter sp.

Xylitol is a poly-hydroxy straight-chain five-carbon alcohol that can replace sugar in daily uses without any side effects. Lowered risk of dental carries and bone demineralization further support its involvement in a healthy lifestyle. In addition, its role in the synthesis of various commercial products like glycol, ethanol, and resins etc. increases its market value and makes it one of the most valuable bio-products. Microbial fermentation is a cost-effective and eco-friendly method for xylitol production from agricultural residues as available xylose is reduced to xylitol by Xylose reductase (XR) using an equivalent amount of NADPH as a mediator for electron transfer. Previous literature emphasized the use of fungi and yeast for xylitol production rather than bacteria. In contrast to available reports, the potential of the bacterial isolate was evaluated for xylitol production. The effect of process parameters was observed on xylitol yield in terms of XR activity. Out of sixty-eight bacterial isolates obtained, XYLBV-05 was selected for XR production after screening and was identified as Citrobacter sp. based on morphological, microscopic, and biochemical characteristics. Parametric analysis increased the XR production by 4.12 folds (36.61 U/ml). Preliminary results also proved its efficiency in conversion of biomass hydrolysate to xylitol at lab scale but further efforts are needed for xylitol production using agro-industrial lignocellulosic biomass at a large scale which will not only aid in the generation of revenue as a result of value-added products but will also help in environment conservation.

Biovalorization of Lignocellulosic Materials for Xylitol Production by the Yeast Komagataella pastoris

The main goal of this study was to screen different lignocellulosic materials for their ability to support the cell growth of the yeast Komagataella pastoris and the production of xylitol. Several lignocellulosic materials, namely banana peels, brewer’s spent grains (BSGs), corncobs, grape pomace, grape stalks, and sawdust, were subjected to dilute acid hydrolysis to obtain sugar rich solutions that were tested as feedstocks for the cultivation of K. pastoris. Although the culture was able to grow in all the tested hydrolysates, a higher biomass concentration was obtained for banana peels (15.18 ± 0.33 g/L) and grape stalks (14.58 ± 0.19 g/L), while the highest xylitol production (1.51 ± 0.07 g/L) was reached for the BSG hydrolysate with a xylitol yield of 0.66 ± 0.39 g/g. Cell growth and xylitol production from BSG were improved by detoxifying the hydrolysate using activated charcoal, resulting in a fourfold increase of the biomass production, while xylitol production was improved to 3.97 ± 0.10 g/L. Moreover, concomitant with arabinose consumption, arabitol synthesis was noticed, reaching a maximum concentration of 0.82 ± 0.05 g/L with a yield on arabinose of 0.60 ± 0.11 g/g. These results demonstrate the feasibility of using lignocellulosic waste, especially BSG, as feedstock for the cultivation of K. pastoris and the coproduction of xylitol and arabitol. Additionally, it demonstrates the use of K. pastoris as a suitable microorganism to integrate a zero-waste biorefinery, transforming lignocellulosic waste into two high-value specialty chemicals with high market demand.

Growth of thermotolerant Pichia kudriavzevii UniMAP 3-1 strain for ethanol production using xylose and glucose at different fermentation temperatures

The applications of thermotolerant microorganisms in the production of lignocellulosic bioethanol is the key factor for successful simultaneous saccharification and fermentation process. Thus, this study aimed to isolate a thermotolerant yeast strain that was able to convert both glucose and xylose into ethanol. An analysis based on D1/D2 region of the large-subunit ribosomal DNA identified the isolated strain namely as Pichia kudriavzevii UniMAP 3-1. The growth of this newly isolated yeast was tested with fermentation temperature at 30°C and 40°C on xylose and glucose. P. kudriavzevii UniMAP 3-1 was able to ferment xylose to ethanol at both 30°C and 40°C with a yield of 0.013 g/g and 0.019 g/g with concomitant xylitol yield of 0.24 g/g and 0.25 g/g, respectively. Fermentation of glucose to ethanol was also tested at 30°C and 40°C and the yields were 0.42 g/g and 0.41 g/g, respectively. The potential of this thermotolerant yeast to be used in high-temperature fermentation in both glucose and xylose are proven in this study.

Improvement of enzymatic bioxylitol production from sawdust hemicellulose: optimization of parameters

Enzymatic production of bioxylitol from lignocellulosic biomass (LCB) provides a promising alternative to both chemical and fermentative routes. This study aimed to assess the impacts of catalytic variables on bioxylitol production from wood sawdust using xylose reductase (XR) enzyme and to optimize the bioprocess. Enzyme-based xylitol production was carried out in batch cultivation under various experimental conditions to obtain maximum xylitol yield and productivity. The response surface methodology (RSM) was followed to fine-tune the most significant variables such as reaction time, temperature, and pH, which influence the synthesis of bioxylitol from sawdust hydrolysate and to optimize them. The optimum time, temperature, and pH became were 12.25 h, 35 °C, and 6.5, respectively, with initial xylose 18.8 g/L, NADPH 2.83 g/L, XR 0.027 U/mg, and agitation 100 rpm. The maximum xylitol production was attained at 16.28 g/L with a yield and productivity of 86.6% (w/w) and 1.33 g/L·h, respectively. Optimization of catalytic parameters using sequential strategies resulted in 1.55-fold improvement in overall xylitol production. This study explores a novel strategy for using sawdust hemicellulose in bioxylitol production by enzyme technology.

Novel potential yeast strains for the biotechnological production of xylitol from sugarcane bagasse

AbstractThis study aimed to screen the xylitol‐producing strains of Cyberlindnera xylosilytica and Wickerhamomyces rabaulensis for the bioconversion of the hemicellulosic fraction of sugarcane bagasse. Among the 16 strains tested, two of each species (C. xylosilytica UFMG‐CM‐Y309 and UFMG‐CM‐Y409, and W. rabaulensis UFMG‐CM‐Y3716 and UFMG‐CM‐Y3747) were selected on the basis of xylitol yield (Yp/s) and xylitol volumetric productivity (Qp) in YPX broth (yeast extract, 10 g L−1; peptone, 20 g L−1; and d‐xylose, 60 g L−1). These strains were cultivated in sugarcane bagasse hemicellulosic hydrolysate (SCHH) supplemented with ammonium sulfate, rice bran extract, and yeast extract. The xylitol yield was the highest in the strain C. xylosilytica UFMG‐CM‐Y‐309 with a production of 14.06 g L−1; xylitol yield, 0.63 g g−1; xylitol volumetric productivity, 0.20 g L−1 h−1. Xylitol yields ranged from 14% to 74% above those of other xylitol‐production yeast species. This work demonstrates the potential of biotechnological application of these yeasts for xylitol production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Valorization of Corncob by Hydrolysis-Hydrogenation to Obtain Xylitol Under Mild Conditions

The pretreatment of biomass represents a large energy expenditure in the production of sugar alcohols. Current research efforts are focused on integrating catalytic processes to decrease operating time and reduce energy and raw material consumption. In this work, the hydrolysis-hydrogenation of hemicellulose for xylitol production direct from corncob was studied. It was used two strategies of hydrogenation: H2 gas under pressure, and isopropanol as H2 donor. The importance of the presence of H2SO4 and 5% Ru/C catalyst in the reaction medium was analyzed. It was considered the use of H2 pressure (2 MPa) and employing isopropanol (water-isopropanol 1:3) as a source of hydrogen. The reaction products were determined by HPLC. The 5% Ru/C catalyst was active and selective for the conversion of xylose to xylitol. To promote the hydrolysis of the hemicellulose fraction of the corncob into xylose, the addition of acid was necessary. Under mild conditions (0.1% H2SO4, 413 K), xylose was detected as the main product, indicating the good selectivity of the first hemicellulose conversion step. A xylitol yield was 19% under H2 pressure while with isopropanol 7% was obtained. The intermediate purification step was eliminated because as xylose was formed it was simultaneously hydrogenated to produce xylitol in the presence of Ru catalyst. Cellulose remained intact in the solid residue and could be used to obtain other products, such as glucose, sorbitol, ethanol, or charcoal.

Prospective evaluation of xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii with sustainable agricultural residues

In this study, agro-wastes, including corncob, rice straw, and wheat straw, were used as substrate for xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii. The experiments were performed using batch fermentation using hemicellulose hydrolyzate as substrate under optimum levels of the screened significant nutrients and process variables. Screening and optimization were carried out for all the systems using statistical methods based on experimental designs. Kinetics and modeling for xylitol production were developed using the logistic model for microbial growth, substrate utilization kinetics for the substrate utilization, and Luedeking-Piret model for the product formation. The model parameters were compared for all xylitol production carried out using pretreated hemicellulose hydrolyzates from corncob, rice straw, and wheat straw. Experimental analysis and modeling results revealed a maximum xylitol yield when corncob was hydrolyzed with Pachysolen tannophilus.

Optimized Bioconversion of Xylose Derived from Pre-Treated Crop Residues into Xylitol by Using Candida boidinii

Crop residues can serve as low-cost feedstocks for microbial production of xylitol, which offers many advantages over the commonly used chemical process. However, enhancing the efficiency of xylitol fermentation is still a barrier to industrial implementation. In this study, the effects of oxygen transfer rate (OTR) (1.1, 2.1, 3.1 mmol O2/(L × h)) and initial xylose concentration (30, 55, 80 g/L) on xylitol production of Candida boidinii NCAIM Y.01308 on xylose medium were investigated and optimised by response surface methodology, and xylitol fermentations were performed on xylose-rich hydrolysates of wheat bran and rice straw. High values of maximum xylitol yields (58–63%) were achieved at low initial xylose concentration (20–30 g/L) and OTR values (1.1–1.5 mmol O2/(L × h)). The highest value for maximum xylitol productivity (0.96 g/(L × h)) was predicted at 71 g/L initial xylose and 2.7 mmol O2/(L × h) OTR. Maximum xylitol yield and productivity obtained on wheat bran hydrolysate were 60% and 0.58 g/(L × h), respectively. On detoxified and supplemented hydrolysate of rice straw, maximum xylitol yield and productivity of 30% and 0.19 g/(L × h) were achieved. This study revealed the terms affecting the xylitol production by C. boidinii and provided validated models to predict the achievable xylitol yields and productivities under different conditions. Efficient pre-treatments for xylose-rich hydrolysates from rice straw and wheat bran were selected. Fermentation using wheat bran hydrolysate and C. boidinii under optimized condition is proved as a promising method for biotechnological xylitol production.

Techno‐economic analysis of sugar production from lignocellulosic biomass with utilization of hemicellulose and lignin for high‐value co‐products

AbstractSugar derived from lignocellulosic biomass is an important intermediate product, often used for the production of biofuels and value‐added chemicals. It is therefore essential to understand and reduce the production costs of sugar derived from lignocellulosic biomass. This study evaluates the economic feasibility of a biorefinery producing sugar from lignocellulosic biomass using a combination of autohydrolysis and mechanical refining pretreatment. This biorefinery is self‐sufficient in energy, producing excess electricity for sale. The minimum sugar selling price (MSSP) that achieves a zero net present value is $446/metric ton. The possibility of using the two main by‐products, dissolved hemicellulose and lignin, for the production of high‐value products, xylitol and polyol, is also evaluated. When dissolved hemicellulose is used for xylitol production, the MSSP decreases to $347/metric ton. When lignin is liquefied to produce polyol, the MSSP is further reduced to $342/metric ton. External energy (natural gas) must be purchased if xylitol and polyol are produced. An analysis of capital and operating costs reveals that, although the production of xylitol and polyol incurs additional capital investment, their correspondingly high values outweigh the additional capital costs. Sensitivity analysis results indicate that efficient recovery and recycling of expensive chemicals like acetone and glycerol are key to the success of the biorefinery. Yields of xylitol and polyol also have strong impacts on the process economics. © 2020 Society of Industrial Chemistry and John Wiley & Sons Ltd

Process scale-up of an efficient acid-catalyzed steam pretreatment of rice straw for xylitol production by C. Tropicalis MTCC 6192

The present study focuses on operational parameters for the efficient acid catalyzed rice straw pretreatment process for xylitol production. 75.77 % xylose yield was attained when the 24 h presoaked rice straw (≤10 mm or ≤ 15 mm) in 1.5 % (v/v) H2SO4 was pretreated in the same reactor at 121 °C for 30 min. Neutralization with barium hydroxide produced insoluble salt and noticeably reduced HMF and furfurals. Xylitol yield of 0.6 g/g of xylose, was achieved by fermenting rice straw hydrolysate medium with C. tropicalis MTCC 6192. This two-step process of production of xylitol from xylose rich hydrolysate is much simpler and produced minimal inhibitors including organic acids such as acetic acid. This process is modified for upscaling at optimized parameters and will simultaneously minimize the pollution problem caused by rice straw and is also promising for commercial scale.

Improving xylitol yield by deletion of endogenous xylitol-assimilating genes: a study of industrial Saccharomyces cerevisiae in fermentation of glucose and xylose.

Engineered Saccharomyces cerevisiae can reduce xylose to xylitol. However, in S.cerevisiae, there are several endogenous enzymes including xylitol dehydrogenase encoded by XYL2, sorbitol dehydrogenases encoded by SOR1/SOR2 and xylulokinase encoded by XKS1 may lead to the assimilation of xylitol. In this study, to increase xylitol accumulation, these genes were separately deleted through CRISPR/Cas9 system. Their effects on xylitol yield of an industrial S. cerevisiae CK17 overexpressing Candida tropicalis XYL1 (encoding xylose reductase) were investigated. Deletion of SOR1/SOR2 or XKS1 increased the xylitol yield in both batch and fed-batch fermentation with different concentrations of glucose and xylose. The analysis of the transcription level of key genes in the mutants during fed-batch fermentation suggests that SOR1/SOR2 are more crucially responsible for xylitol oxidation than XYL2 under the genetic background of S.cerevisiae CK17. The deletion of XKS1 gene could also weaken SOR1/SOR2 expression, thereby increasing the xylitol accumulation. The XKS1-deleted strain CK17ΔXKS1 produced 46.17g/L of xylitol and reached a xylitol yield of 0.92g/g during simultaneous saccharification and fermentation (SSF) of pretreated corn stover slurry. Therefore, the deletion of XKS1 gene provides a promising strategy to meet the industrial demands for xylitol production from lignocellulosic biomass.

Xylitol production from non-detoxified Napiergrass hydrolysate using a recombinant flocculating yeast strain

Xylose derived from lignocellulose can be utilized to produce ethanol and other high-value chemicals, such as xylitol. The xylitol production through fermentation of lignocellulosic hydrolysate by microorganisms offers advantages of high product yield, high selectivity, and efficacy in mild conditions. In this study, non-detoxified hemicellulose hydrolysate from napiergrass was used for xylitol production by a recombinant flocculating strain of Saccharomyces cerevisiae. An optimization study was conducted with the strain at 35 °C. A promising xylitol yield of 0.96 g/g xylose with no addition of glucose required during the fermentation process, which suggests an extensive potential improvement for the economics of lignocellulosic xylitol production.

Efficient Synthesis of Sugar Alcohols under Mild Conditions Using a Novel Sugar-Selective Hydrogenation Catalyst Based on Ruthenium Valence Regulation

Sugar alcohols are the prominent alternatives of sugars in food, medical, and health industries. The ruthenium supported on multiwalled carbon nanotubes (Ru/MWCNTs) catalysts were prepared based on the Ru valence regulation strategy and applied for selective sugar hydrogenation to prepare various sugar alcohols including xylitol, arabinitol, sorbitol, mannitol, and galactitol for the first time, with high selectivity (>99.0%) and yield (>98.0%) under mild conditions (≤110 °C, 3.0 MPa H2 pressure). The hydrogenation reaction of xylose was further optimized and under mild conditions (100 °C, 3.0 MPa H2 pressure, and 500 rpm), which were lower than ever reported for high efficient synthesis of xylitol, 99.8% xylose conversion and 99.0% xylitol yield were achieved after 120 min of reaction.

Xylitol Production from Exhausted Olive Pomace by Candida boidinii

In this work, the production of xylitol from a hemicellulosic hydrolysate of exhausted olive pomace (EOP), a residue originated in the olive oil production process by Candida boidinii, was assessed. The hydrolysate was obtained by dilute acid pretreatment of EOP at 170 °C and 2% H2SO4 (w/v). A previous detoxification step of the hydrolysate was necessary, and its treatment with activated charcoal and ion-exchange resin was evaluated. Prior to fermentation of the hydrolysate, fermentation tests in synthetic media were performed to determine the maximum xylitol yield and productivity that could be obtained if inhibitory compounds were not present in the medium. In addition, the glucose existing in the media exerted a negative influence on xylitol production. A maximum xylitol yield of 0.52 g/g could be achieved in absence of inhibitor compounds. Fermentation of the hemicellulosic hydrolysate from EOP after detoxification with ion-exchange resin resulted in a xylitol yield of 0.43 g/g.

Valorization of the sugarcane bagasse and straw hemicellulosic hydrolysate through xylitol bioproduction: effect of oxygen availability and sucrose supplementation as key factors

Sugarcane agroindustry, one of the most important in Brazilian economy, can diversify its product portfolio in a biorefinery context through the use of by-products as feedstocks to produce bioenergy and high-added value chemicals, such as xylitol, which is a sweetener with applications in the food and pharmaceutical industries and with a growing market. Opportunities for the integration of xylitol bioproduction in a sugarcane biorefinery can be based on the valorization of bagasse, straw, and molasses, which are feedstocks with high content of carbohydrates, specifically xylose from the hemicellulosic fraction of the lignocellulosic biomasses, and sucrose from molasses that can act as co-substrate on this bioprocess. Xylitol bioproduction from the hemicellulosic hydrolysate of the sugarcane bagasse and straw mixture was herein investigated. Particularly, the effects of sucrose supplementation to the medium on the fermentative performance of Candida tropicalis depending on its initial concentration and oxygen availability (expressed as KLa), which is one of the most important factors for this bioprocess, are discussed. Xylitol yield (0.86 gg−1) and volumetric productivity (0.51 gL−1 h−1) were concomitantly maximized by using sucrose (0.91 gL−1) and KLa (6.5 h−1) within the optimization range. Furthermore, the addition of sugarcane molasses to the hemicellulosic hydrolysate improved xylitol production, in comparison with the conventional supplementation. Scientific background is given to contribute to supporting the potential integration of xylitol bioproduction to a sugarcane biorefinery, which may enhance both the feasibility of this bioprocess and sugarcane agroindustry valorization based on the applications and growing xylitol market.

Hydrolysis of Corncob Hemicellulose by Solid Acid Sulfated Zirconia and Its Evaluation in Xylitol Production

Corncob is an abundant agricultural residue containing high content of hemicellulose. In this paper, the hemicellulosic hydrolysate was prepared from the hydrolysis of corncob using the solid acid sulfated zirconia as a catalyst. According to response surface analysis experiments, the optimum conditions for preparing hemicellulosic hydrolysate catalyzed by sulfated zirconia were determined as follows: solid (sulfated zirconia)-solid (corncob) ratio was 0.33, solid (corncob)-liquid (water) ratio was 0.09, temperature was 153 °C, and time was 5.3 h. Under the optimized conditions, the soluble sugar concentration was 30.12 g/L with a yield of 033 g/g corncob. Subsequently, xylitol production from the resulting hemicellulosic hydrolysate was demonstrated by Candida tropicalis, and results showed that the yield of xylitol from the hemicellulosic hydrolysate could be significantly improved on a basis of decolorization and detoxification before fermentation. The maximum yield of xylitol from the hemicellulosic hydrolysate fermented by C. tropicalis was 0.76 g/g. This study provides a new attempt for xylitol production from the hemicellulosic hydrolysate.

Effect of pH on xylitol production by Candida species from a prairie cordgrass hydrolysate.

Using hydrolysates of the North American prairie grass prairie cordgrass buffered at pH 4.5, 5.0, 5.5 or 6.0, xylitol production, xylitol yield, cell biomass production and productivity were investigated for three strains of yeast Candida. Of the three strains, the highest xylitol concentration of 20.19g xylitol (g xylose consumed)-1 and yield of 0.89g xylitol (g xylose consumed)-1 were produced by Candida mogi ATCC 18364 when grown for 120h at 30°C on the pH 5.5-buffered hydrolysate-containing medium. The highest biomass level being 7.7gcells (kg biomass)-1 was observed to be synthesized by Candida guilliermondii ATCC 201935 after 120h of growth at 30°C on a pH 5.5-buffered hydrolysate-containing medium. The highest xylitol specific productivity of 0.73g xylitol (g cellsh)-1 was determined for C.guilliermondii ATCC 20216 after 120h of growth at 30°C on a pH 5.0-buffered hydrolysate-containing medium. Xylitol production and yield by the three Candida strains was higher on prairie cordgrass than what was previously observed for the same strains after 120h at 30°C when another North American prairie grass big bluestem served as the plant biomass hydrolysate indicating that prairie cordgrass may be a superior plant biomass substrate.

Multi-scale study of the integrated use of the carbohydrate fractions of sugarcane bagasse for ethanol and xylitol production

A multi-scale study of sugarcane bagasse (SB) pretreatments and integrated developments for use of its carbohydrates portions for ethanol and xylitol production, are presented. In a first approach, after SB acid hydrolysis, hemicellulosic ethanol production was investigated, verifying ethanol yield of 0.31 g/g and volumetric productivity (QP) of 0.1 g/L.h. Xylitol production was also studied, showing xylitol yield and QP of 0.61 g/g and 0.38 g/L.h, respectively. Thus, remaining cellulignin from acid pretreatment was submitted to alkaline hydrolysis followed by Semi-Simultaneous Saccharification and Co-fermentation in sequential processes to ethanol production, by using mixture of SB hemicellulosic and enzymatic hydrolysate as carbon source, verifying QP of 0.6 g/L.h. Moreover, a biomass multi-scale study was conducted by analysis of MEV, X-Ray, FTIR and Ramman Spectroscopy, verifying clear changes in SB structure along each pretreatment. These novel approaches indicated the potential of these integrated use of SB carbohydrates portion for bioproducts obtaining from SB in sustainable processes.

Physicochemical Properties of Xylitol Crystals from Oil Palm Empty Fruit Bunches Hydrolysate

Xylitol, a low-calorie sugar made up of five carbon atoms, had the valuable characteristics suitably applied for pharmaceutical and food industries. This sugar can be produced from oil palm empty fruit bunches (OPEFB) through hydrolysis and followed by fermentation. The xylitol in the fermentation broth requires the downstream process to obtain the final product with high purity and yield. Among a series of xylitol downstream process, crystallization becomes a critical step since this process determines the properties of final products. The objective of this study was to evaluate the effect of evaporation temperature (55°C and 70°C) and seeding addition (0%, 0.1%, 0.5%, 1 %) in the crystallization step on the physicochemical properties of xylitol crystals obtained from the OPEFB hydrolysate. The main evaluation criteria were crystal contents, purity, melting point, water content, hygroscopicity, solubility, caloric content, and crystal xylitol yield. The result showed that the crystal form obtained was relatively sticky and had lower purity than commercial ones because the concentration of xylitol solution increased after evaporation. The differences of physicochemical properties of the crystals such as the purity, porosity, yield and crystal form were influenced by evaporation temperature. The crystals formed by 70°C evaporation temperature produced the crystals with higher caloric value and purity, but it had lower hygroscopicity and moisture content than crystals formed by 55°C. However, the percentage of seeding gave an insignificant impact on xylitol crystal properties.