Purification of Xylitol from Fermented Hemicellulosic Hydrolyzate Using Liquid–Liquid Extraction and Precipitation Techniques

Xylitol was produced by Candida guilliermondii by fermentation of sugarcane bagasse hemicellulosic hydrolysate. Undesirable impurities were extracted from the broth using either ethyl acetate, chloroform or dichloromethane. The best results on clarification of the broth without xylitol loss were obtained with ethyl acetate. When ethanol, acetone or tetrahydrofuran were used for precipitation of impurities, only tetrahydrofuran clarified the fermented broth, but a high xylitol loss (~30%) was observed.     

Xylitol production from corn fiber and sugarcane bagasse hydrolysates by Candida tropicalis

A natural isolate, Candida tropicalis was tested for xylitol production from corn fiber and sugarcane bagasse hydrolysates. Fermentation of corn fiber and sugarcane bagasse hydrolysate showed xylose uptake and xylitol production, though these were very low, even after hydrolysate neutralization and treatments with activated charcoal and ion exchange resins. Initial xylitol production was found to be 0.43 g/g and 0.45 g/g of xylose utilised with corn fiber and sugarcane bagasse hydrolysate respectively. One of the critical factors for low xylitol production was the presence of inhibitors in these hydrolysates. To simulate influence of hemicellulosic sugar composition on xylitol yield, three different combinations of mixed sugar control experiments, without the presence of any inhibitors, have been performed and the strain produced 0.63 g/g, 0.68 g/g and 0.72 g/g of xylose respectively. To improve yeast growth and xylitol production with these hydrolysates, which contain inhibitors, the cells were adapted by sub culturing in the hydrolysate containing medium for 25 cycles. After adaptation the organism produced more xylitol 0.58 g/g and 0.65 g/g of xylose with corn fiber hydrolysate and sugarcane bagasse hydrolysate respectively.     

Radiation and fermentation treatment of cellulosic wastes

The effect of radiation pasteurization of sugar cane bagasse and rice straw and fermentation using various strains of fungi were studied for upgrading of cellulosic wastes. The initial contamination by fungi and aerobic bacteria both in bagasse and straw was high. The doses of 30 kGy for sterilization and 8 kGy for elimination of fungi were required. Irradiation effect showed that rice straw contained comparatively radioresistant microorganisms. It was observed that all the fungi (Hericium erinacium, Pleurotus djamor, Ganoderma lucidum, Auricularia auricula, Lentinus sajor-caju, Coriolus versicolor, Polyporus arcularius, Coprinus cinereus) grow extending over the entire substrates during one month after inoculation in irradiated bagasse and rice straw with 3% rice bran and 65% moisture content incubated at 30°C. Initially, sugar cane bagasse and rice straw substrates contained 39.4% and 25.9% of cellulose, 22.9% and 26.9% of hemicellulose, and 19.6% and 13.9% of lignin + cutin, respectively. Neutral detergent fibre (NDF) values decreased significantly in sugar cane bagasse fermented byG. lucidum, A. auricula andP. arcularius, and in rice straw fermented by all the 8 strains of fungi. Acid detergent fibre (ADF) values also decreased in bagasse and rice straw fermented by all the fungi.P. arcularius, H. erinacium, G. lucidum andC. cinereus were found to be the most effective strains for delignification of sugar cane bagasse.     

酵母发酵蔗渣半纤维素水解物生产木糖酶

采用二次正交旋转组合设计研究了蔗渣半纤维素水解过程中硫酸浓度与液 固比对木糖收率的影响。回归分析表明 ,这两个因素与木糖的收率之间存在显著的回归关系。通过回归方程优化水解条件 ,当硫酸浓度 2 .4g L ,液 固 =6 .2 ,在蒸汽压力 2 .5× 10 4Pa的条件下水解 2 .5h ,10 0g蔗渣可水解生成木糖约 2 4g。大孔树脂吸附层析处理蔗渣半纤维素水解物 ,能有效地减少其中的酵母生长抑制物含量 ,显著改善水解物的发酵性能。用大孔树脂在pH 2条件下处理过的蔗渣半纤维素水解物作基质 ,含木糖 2 0 0g L ,产木糖醇酵母菌株CandidatropicalisAS2 .1776发酵 110h耗完基质中的木糖 ,生成木糖醇 12 7g L ,产物转化率 0 .6 4(木糖醇g 木糖g) ,产物生成速率 1.15g L·h .     

Fermentation of sugar cane bagasse hemicellulose hydrolysate to l(+)-lactic acid by a thermotolerant acidophilic Bacillus sp.**

Sugar cane bagasse hemicellulose, hydrolyzed by dilute H2SO4, supplemented with mineral salts and 0.5% corn steep liquor, was fermented to L(+)-lactic acid using a newly isolated strain of Bacillus sp. In batch fermentations at 50 degrees C and pH 5, over 5.5% (w/v) L(+)-lactic acid was produced (89% theoretical yield; 0.9 g lactate per g sugar) with an optical purity of 99.5%.     

Comparative hydrolysis and fermentation of sugarcane and agave bagasse

Sugarcane and agave bagasse samples were hydrolyzed with either mineral acids (HCl), commercial glucanases or a combined treatment consisting of alkaline delignification followed by enzymatic hydrolysis. Acid hydrolysis of sugar cane bagasse yielded a higher level of reducing sugars (37.21% for depithed bagasse and 35.37% for pith bagasse), when compared to metzal or metzontete (agave pinecone and leaves, 5.02% and 9.91%, respectively). An optimized enzyme formulation was used to process sugar cane bagasse, which contained Celluclast, Novozyme and Viscozyme L. From alkaline–enzymatic hydrolysis of sugarcane bagasse samples, a reduced level of reducing sugar yield was obtained (11–20%) compared to agave bagasse (12–58%). Selected hydrolyzates were fermented with a non-recombinant strain of Saccharomyces cerevisiae. Maximum alcohol yield by fermentation (32.6%) was obtained from the hydrolyzate of sugarcane depithed bagasse. Hydrolyzed agave waste residues provide an increased glucose decreased xylose product useful for biotechnological conversion.     

Pyrolysis of olive residue and sugar cane bagasse: non-isothermal thermogravimetric kinetic analysis

Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2-50 K min(-1) providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538-543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600-607 K). The two biomass mainly devolatilized around 473-673 K, with total volatile yield of about 70-75%. The char in final residue was about 19-26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa-Flynn-Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10-40% conversion range have a value of 153-162 kJ mol(-1) and 168-180 kJ mol(-1) for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50-80% conversion range, this value is 204-215 kJ mol(-1) and 231-240 kJ mol(-1) for the cellulose degradation of olive residue and sugar cane bagasse, respectively.     

Environmental parameters affecting xylitol production from sugar cane bagasse hemicellulosic hydrolyzate by Candida guilliermondii

The bioconversion of xylose to xylitol by Candida guilliermondii FTI 20037 cultivated in sugar cane bagasse hemicellulosic hydrolyzate was influenced by cell inoculum level, age of inoculum and hydrolyzate concentration. The maximum xylitol productivity (0.75 g L⁻¹ h⁻¹) occurred in tests carried out with hydrolyzate containing 54.5 g L⁻¹ of xylose, using 3.0 g L⁻¹ of a 24-h-old inoculum. Xylitol productivity and cell concentration decreased with hydrolyzate containing 74.2 g L⁻¹ of xylose. Received 02 February 1996/ Accepted in revised form 15 November 1996     

Reductively aminated D-xylose-albumin conjugate as the immunogen for generation of IgG and IgE antibodies specific to D-xylitol, a haptenic allergen

Sugar alcohols are widely used as food additives and drug excipients. Xylitol, a five-carbon sugar alcohol, and a low-calorie alternative sweetener to sucrose (approx 40% fewer calories), has enjoyed an enviable record of safety, and allergic reactions to xylitol are very rare. A case of oral erosive eczema to xylitol has been reported recently [Hanakawa, Y., Hanakawa, Y., Tohyama, M., Yamasaki, K., Hashimoto, K. (2005) Xylitol as a causative agent of oral erosive eczema. Brit. J. Dermatol. 152, 821-822]. Xylitol does not contain any reactive groups; hence, it is nonimmunogenic. In order to explain the immunogenicity of xylitol, polyclonal antibodies to xylitol have been raised using the reductive aminated product of D-xylose conjugated to bovine serum albumin (BSA) as the immunogen. Rabbits immunized with xylitol-BSA conjugate (52 haptens/molecule) gave a good antibody response. Purification of antixylitol antibodies was carried out using hapten-affinity chromatography on xylitol-keyhole limpet hemocyanin-Sepharose CL-6B; the yield was approximately 40 microg/mL of rabbit immune serum. Purified xylitol-specific antibodies appeared to be homogeneous by native PAGE with a pI of approximately 7.2 by isoelectric focusing. Although the purified antibodies are specific for the xylitoyl moiety of xylitol-protein conjugates, they reacted equally well with the Schiff base conjugate of xylosyl-protein conjugates (68% cross-reactivity) indicating that carbons 2 to 5 of xylitol act as an epitope. Xylitol antibodies showed excellent specificity towards xylitol and <4.4% cross-reactivity with D-xylose and various sugar alcohols except ribitol and galactitol, which showed approximately 11% and 8% cross-reactivity, respectively. D-Xylitol-BSA conjugate was used to raise IgE antibodies in BALB/c mice by repeated intradermal administration. Passive cutaneous anaphylaxis using the immune sera confirmed the haptenic nature of xylitol.     

Alkali‐based AFEX pretreatment for the conversion of sugarcane bagasse and cane leaf residues to ethanol

Sugarcane is one of the major agricultural crops cultivated in tropical climate regions of the world. Each tonne of raw cane production is associated with the generation of 130 kg dry weight of bagasse after juice extraction and 250 kg dry weight of cane leaf residue postharvest. The annual world production of sugarcane is ～1.6 billion tones, generating 279 MMT tones of biomass residues (bagasse and cane leaf matter) that would be available for cellulosic ethanol production. Here, we investigated the production of cellulosic ethanol from sugar cane bagasse and sugar cane leaf residue using an alkaline pretreatment: ammonia fiber expansion (AFEX). The AFEX pretreatment improved the accessibility of cellulose and hemicelluloses to enzymes during hydrolysis by breaking down the ester linkages and other lignin carbohydrate complex (LCC) bonds and the sugar produced by this process is found to be highly fermentable. The maximum glucan conversion of AFEX pretreated bagasse and cane leaf residue by cellulases was ～85%. Supplementation with hemicellulases during enzymatic hydrolysis improved the xylan conversion up to 95–98%. Xylanase supplementation also contributed to a marginal improvement in the glucan conversion. AFEX‐treated cane leaf residue was found to have a greater enzymatic digestibility compared to AFEX‐treated bagasse. Co‐fermentation of glucose and xylose, produced from high solid loading (6% glucan) hydrolysis of AFEX‐treated bagasse and cane leaf residue, using the recombinant Saccharomyces cerevisiae (424A LNH‐ST) produced 34–36 g/L of ethanol with 92% theoretical yield. These results demonstrate that AFEX pretreatment is a viable process for conversion of bagasse and cane leaf residue into cellulosic ethanol. Biotechnol. Bioeng. 2010;107: 441–450. © 2010 Wiley Periodicals, Inc.     

Leishmania amazonensis: xylitol as inhibitor of macrophage infection and stimulator of macrophage nitric oxide production

Xylitol is a sugar alcohol being explored for clinical uses. The aim was to evaluate the effects of xylitol on Leishmania amazonensis-infected J774A.1 macrophages. Macrophages were infected with L. amazonensis for 3h, washed and incubated with 2.5 or 5.0% xylitol for 24, 48, and 72 h at 37 degrees C. Infection indexes for macrophages incubated only in medium were compared to those treated with xylitol. Cell viability and nitric oxide production were determined each time. Xylitol did not affect L. amazonensis or J774A.1 cell viabilities. Xylitol at 5.0% stimulated nitric oxide production by macrophages at 72 h (p<0.01). At 2.5 and 5.0%, xylitol inhibited nitric oxide production by L. amazonensis at 48 h (p<0.05) when compared to control. Infection indexes were significantly lower at 72 h (p<0.05), (16.9% and 9.6%) in cells cultivated with 2.5 and 5.0% xylitol, respectively, compared to control (38.4%). Results suggest a potential leishmanicidal action of the xylitol on infected macrophages.     

Techno-economic evaluation of 2nd generation bioethanol production from sugar cane bagasse and leaves integrated with the sugar-based ethanol process

Background

Bioethanol produced from the lignocellulosic fractions of sugar cane (bagasse and leaves), i.e. second generation (2G) bioethanol, has a promising market potential as an automotive fuel; however, the process is still under investigation on pilot/demonstration scale. From a process perspective, improvements in plant design can lower the production cost, providing better profitability and competitiveness if the conversion of the whole sugar cane is considered. Simulations have been performed with AspenPlus to investigate how process integration can affect the minimum ethanol selling price of this 2G process (MESP-2G), as well as improve the plant energy efficiency. This is achieved by integrating the well-established sucrose-to-bioethanol process with the enzymatic process for lignocellulosic materials. Bagasse and leaves were steam pretreated using H₃PO₄ as catalyst and separately hydrolysed and fermented.

Results

The addition of a steam dryer, doubling of the enzyme dosage in enzymatic hydrolysis, including leaves as raw material in the 2G process, heat integration and the use of more energy-efficient equipment led to a 37 % reduction in MESP-2G compared to the Base case. Modelling showed that the MESP for 2G ethanol was 0.97 US$/L, while in the future it could be reduced to 0.78 US$/L. In this case the overall production cost of 1G + 2G ethanol would be about 0.40 US$/L with an output of 102 L/ton dry sugar cane including 50 % leaves. Sensitivity analysis of the future scenario showed that a 50 % decrease in the cost of enzymes, electricity or leaves would lower the MESP-2G by about 20%, 10% and 4.5%, respectively.

Conclusions

According to the simulations, the production of 2G bioethanol from sugar cane bagasse and leaves in Brazil is already competitive (without subsidies) with 1G starch-based bioethanol production in Europe. Moreover 2G bioethanol could be produced at a lower cost if subsidies were used to compensate for the opportunity cost from the sale of excess electricity and if the cost of enzymes continues to fall.     

Fed-batch culture of Candida guilliermondii FTI 20037 for xylitol production from sugar cane bagasse hydrolysate

A fed-batch culture system was used to study xylitol production by Candida guilliermondii FTI 20037 in a synthetic and a sugar cane bagasse hydrolysate medium. The values achieved for xylitol yield and volumetric productivity were, respectively, 0 · 84 g g⁻¹ and 0 · 64 g l⁻¹ h⁻¹ using the synthetic medium and 0 · 78 g g⁻¹ and 0 · 62 g l⁻¹ h⁻¹ using the hydrolysate medium.     

Microbial production of xylitol from D-xylose and sugarcane bagasse hemicellulose using newly isolated thermotolerant yeast Debaryomyces hansenii

A thermotolerant yeast capable of fermenting xylose to xylitol at 40°C was isolated and identified as a strain of Debaryomyces hansenii by ITS sequencing. This paper reports the production of xylitol from D-xylose and sugarcane bagasse hemicellulose by free and Ca-alginate immobilized cells of D. hansenii. The efficiency of free and immobilized cells were compared for xylitol production from D-xylose and hemicellulose in batch culture at 40°C. The maximum xylitol produced by free cells was 68.6 g/L from 100 g/L of xylose, with a yield of 0.76 g/g and volumetric productivity 0.44 g/L/h. The yield of xylitol and volumetric productivity were 0.69 g/g and 0.28 g/L/h respectively from hemicellulosic hydrolysate of sugarcane bagasse after detoxification with activated charcoal and ion exchange resins. The Ca-alginate immobilized D. hansenii cells produced 73.8 g of xylitol from 100 g/L of xylose with a yield of 0.82 g/g and volumetric productivity of 0.46 g/L/h and were reused for five batches with steady bioconversion rates and yields.     

Influence of the burning of sugar cane prior to its harvesting upon the production of single-cell protein from bagasse pith

Summary A culture of Cellulomonas sp. and Bacillus subtilis was grown using sugar cane bagasse pith from unburnt sugar cane (UCP) as the source of carbohydrates. The yield and production values were proved to be higher than those obtained with burnt sugar cane (BCP).For UCP the maximum protein production was 7.8 g/l, the cellulolytic activity being 70 %, with a protein/hydrolyzed pith yield of 22 %. For BCP, the maximum protein value was 4.6 g/l, with a cellulolytic activity of 55 % and a protein/hydrolyzed pith of 17 %.The possibility of a chemical inhibitor being present in BCP is discarded because of the alkaline pretreatment and the results obtained on treating the pith from burnt cane with a benzene-ethanol (2:1) mixture. These results were the same as the ones obtained without the benzene-ethyl alcohol mixture extraction.     

Evaluation of holocellulase production by plant-degrading fungi grown on agro-industrial residues

Agaricus brasiliensis CS1, Pleurotus ostreatus H1 and Aspergillus flavus produced holocellulases when grown in solid and submerged liquid cultures containing agro-industrial residues, including sugar cane bagasse and dirty cotton residue, as substrates. These isolates proved to be efficient producers of holocellulases under the conditions used in this screening. Bromatological analysis of agro-industrial residues showed differences in protein, fiber, hemicellulose, cellulose and lignin content. Maximal holocellulase activity (hemicellulase, cellulase and pectinase) was obtained using solid-state cultivation with 10% substrate concentration. In this case, remarkably high levels of xylanase and polygalacturonase activity (4,008 and 4,548 IU/l, respectively) were produced by A. flavus when grown in media containing corn residue, followed by P. ostreatus H1 with IU/l values of 1,900 and 3,965 when cultivated on 5% and 10% sugar cane bagasse, respectively. A. brasiliensis CS1 showed the highest reducing sugar yield (11.640 mg/ml) when grown on medium containing sugar cane bagasse. A. brasiliensis was also the most efficient producer of protein, except when cultivated on dirty cotton residue, which induced maximal production in A. flavus. Comparison of enzymatic hydrolysis of sugar cane bagasse and dirty cotton residue by crude extracts of A. brasiliensis CS1, P. ostreatus H1 and A. flavus showed that the best reducing sugar yield was achieved using sugar cane bagasse as a substrate.     

Draw-fill batch culture mode for production of xylanases by <Emphasis Type="Italic">Cellulomonas flavigena</Emphasis> on sugar cane bagasse

Draw-fill culture was evaluated as a method for xylanase production by Cellulomonas flavigena on sugar cane bagasse. Specific xylanase activity and volumetric xylanase activities were measured by harvesting 50%, 55%, 60% and 70% of fermented broth at the end of each subculture. Maximum specific (64 IU mg(-1) protein) and volumetric (166 IU ml(-1)) xylanase activities were obtained by harvesting 50-55% of broth. Values were 3.4 and 3.8 times greater than those obtained in batch cultures carried out under the same conditions. Enzyme productivity of 4.2 IU ml(-1) h(-1) was significantly greater than that obtained in continuous cultures (2.4 IU ml(-1) h(-1)) (P<0.05).     

Enzymatic saccharification of sugar cane bagasse by continuous xylanase and cellulase production from cellulomonas flavigena PR‐22

Cellulase (CMCase) and xylanase enzyme production and saccharification of sugar cane bagasse were coupled into two stages and named enzyme production and sugar cane bagasse saccharification. The performance of Cellulomonas flavigena (Cf) PR‐22 cultured in a bubble column reactor (BCR) was compared to that in a stirred tank reactor (STR). Cells cultured in the BCR presented higher yields and productivity of both CMCase and xylanase activities than those grown in the STR configuration. A continuous culture with Cf PR‐22 was run in the BCR using 1% alkali‐pretreated sugar cane bagasse and mineral media, at dilution rates ranging from 0.04 to 0.22 1/h. The highest enzymatic productivity values were found at 0.08 1/h with 1846.4 ± 126.4 and 101.6 ± 5.6 U/L·h for xylanase and CMCase, respectively. Effluent from the BCR in steady state was transferred to an enzymatic reactor operated in fed‐batch mode with an initial load of 75 g of pretreated sugar cane bagasse; saccharification was then performed in an STR at 55°C and 300 rpm for 90 h. The constant addition of fresh enzyme as well as the increase in time of contact with the substrate increased the total soluble sugar concentration 83% compared to the value obtained in a batch enzymatic reactor. This advantageous strategy may be used for industrial enzyme pretreatment and saccharification of lignocellulosic wastes to be used in bioethanol and chemicals production from lignocellulose. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:321–326, 2016     

A rare sugar xylitol. Part II: biotechnological production and future applications of xylitol

Xylitol is the first rare sugar that has global markets. It has beneficial health properties and represents an alternative to current conventional sweeteners. Industrially, xylitol is produced by chemical hydrogenation of d-xylose into xylitol. The biotechnological method of producing xylitol by metabolically engineered yeasts, Saccharomyces cerevisiae or Candida, has been studied as an alternative to the chemical method. Due to the industrial scale of production, xylitol serves as an inexpensive starting material for the production of other rare sugars. The second part of this mini-review on xylitol will look more closely at the biotechnological production and future applications of the rare sugar, xylitol.     

An image method to evaluate bagasse fiber dimensions

In the last 25 years the amount of textile nonwovens used for industrial and commercial applications increased more than 10 times. Bagasse fiber, a by-product from sugar cane industry, provides a natural resource for nonwoven industries. Even though underrated as a potential fiber, bagasse comes more and more into attention because of the increasing concern for disposal of agricultural residuals and the need for enhancing the sugar cane industry’s profitability. However, there is a lack of an instrumental method to evaluate bagasse fiber length and fineness. This paper presents a study on measuring the bagasse fineness using image analysis method. Cross-sections images of bagasse fibers were visualized using Scanning Electronic Microscopy (SEM). The computing software Scion Image was used to measure bagasse fiber length and cross-sectional area. Relationship between fiber fineness and cross-sectional area was analyzed using the statistical method of regression.