Corncob Hemicellulose Research Articles

THE PRELIMINARY STUDY OF ANTIOXIDANT ACTIVITY FROM XYLO-OLIGOSACCHARIDE OF CORNCOB (ZEA MAYS) HYDROLYSIS PRODUCT WITH ENDO-β-XYLANASE ENZYME

Xylo-oligosaccharide derived from corncob hemicellulose has been reported to possess antioxidant activity. In order to assess the effective scavenging of xylo-oligosaccharide, we conducted in vitro studies based on self-made xylo-oligosaccharide with DPPH (2,2diphenyl-1-picrilhydrazil) method. Xylo-oligosaccharide was prepared with enzymatic hydrolysis. The enzyme used for hemicellulose hydrolysis was endo-β-xylanase enzyme from PC-01 isolated bactrerium. PC-01 isolated bacterium used in this study was Pacet hot spring which was isolated from East Java. Endo-β-xylanase enzyme is an extracelluler enzyme. There was about 0.199 U/mL after purification and dialysis process. Hydrolisis product of hemicellulose A and B from corncob were analyzed with TLC (Thin Layer Chromatography) and HPLC (High Performance Liquid Chromatography). This analysis showed that hydrolysis product of hemicellulose B had a lot of xylo-oligosaccharide hydrolysis product of hemicellulose than Xylo-oligosaccharide hydrolysis product of hemicelluloses A. Xylo-olygosaccharide was analyzed as on antioxidant activity. Xylo-oligosaccharide hydrolysis product ofhemicellulose B (IC = 48.96) has higher antioxidant activity than Xylo-oligosaccharide hydrolysis product of hemicellulose A (IC 50 50 = 92.302). The toxicity of xylo-oligosaccharide can be calculated by the value of LC 50 (Lethality concentration). LC of xylooligosaccharide derived from corncob hemicellulose was 400 ppm so that xylo-oligosaccharide has anti tumor activity because xylooligosaccharide has LC 50 < 1000 ppm.

Evaluation of xylitol production using corncob hemicellulosic hydrolysate by combining tetrabutylammonium hydroxide extraction with dilute acid hydrolysis

In this paper, we produced hemicellulosic hydrolysate from corncob by tetrabutylammonium hydroxide (TBAH) extraction and dilute acid hydrolysis combined, further evaluating the feasibility of the resultant corncob hemicellulosic hydrolysate used in xylitol production by Candida tropicalis. Optimized conditions for corncob hemicellulose extraction by TBAH was obtained via response surface methodology: time of 90min, temperature of 60°C, liquid/solid ratio of 12 (v/w), and TBAH concentration of 55%, resulting in a hemicellulose extraction of 80.07% under these conditions. The FT-IR spectrum of the extracted corncob hemicellulose is consistent with that of birchwood hemicellulose and exhibits specific absorbance of hemicelluloses at 1380, 1168, 1050, and 900cm−1. In addition, we found that C. tropicalis can ferment the resulting corncob hemicellulosic hydrolysate with pH adjustment and activated charcoal treatment leading to a high xylitol yield and productivity of 0.77g/g and 2.45g/(Lh), respectively.

An environment friendly and efficient process for xylitol bioconversion from enzymatic corncob hydrolysate by adapted Candida tropicalis

This study reported an environment friendly process for xylitol bioconversion from corncob hemicellulose hydrolysate prepared through xylanolytic enzymes by adapted Candida tropicalis. In order to improve the production of xylanolytic enzymes from Aspergillus terreus, the fermentation medium and growth conditions were optimized. Maximum xylanase (722U/g) and β-xylosidase (196U/g) production were exhibited on wheat bran and corncob (mass ratio of 7:3) medium supplemented with 2% (v/v) NaNO3 and 0.05% (v/v) Tween 80 at pH 6.8, 1:1 (v/w) moisture level, 20% inoculum level and 30°C for 120h of cultivation. For preparation of corncob hemicellulose hydrolysate, the optimum enzymatic hydrolysis conditions contained enzyme dosage (30.6U/g), water addition (19.2mL/g), temperature (48.01°C), pH (5.75). Under these conditions, the sugars of 18.03g/L xylose and 4.87g/L glucose were obtained in 8h. The corncob hemicellulose hydrolysate was used for xylitol fermentation and the maximum xylitol yield of 75.14% was obtained by adapted C. tropicalis after the optimization of fermentation.

Production of xylooligosaccharides from corncob using a crude thermostable endo-xylanase from Streptomyces thermovulgaris TISTR1948 and prebiotic properties

Production of xylooligosaccharides (XOs) from corncob using the thermostable endo-xylanase from Streptomyces thermovulgaris TISTR1948 was investigated using KOH pretreatment, followed by enzymatic hydrolysis. The optimal reaction time for production of XOs was 12 h, after which xylobiose comprised a majority of products, and a low xylose content was observed. The optimal conditions for production of XOs were studied using a central composite design. At an enzyme concentration of 129.43 U/g of substrate, 53.80°C, and pH 6.17, the yield of XOs reached 162.97 mg/g of substrate or 752.15 mg/g of hemicellulose in KOH-pretreated corncob. The prebiotic properties of XOs derived from corncob were also investigated using in vitro fermentation of those XOs with the known probiotic strains Lactobacillus casei TISTR1463, L. lactis TISTR1464, and L. plantarum TISTR1465. XOs derived from corncob were comparable to commercial XOs for an ability to enhance the growth of the specified probiotic lactobacilli.

Optimization of SO2‐catalyzed hydrolysis of corncob for xylose and xylitol production

AbstractBACKGROUNDConventional techniques for corncob hydrolysis were generally based on acid treatment. However, a large number of by‐products and undesirable compounds released during acid hydrolysis process may act as inhibitors to xylitol fermentation. To replace acid hydrolysis, SO2‐catalyzed hydrolysis was used in this study to improve the fermentability of corncob hemicellulose hydrolysate.RESULTSBased on a central composite design (CCD), 20 operations were performed to optimize the process of SO2‐catalyzed hydrolysis by varying SO2 concentration, temperature and reaction time. The optimum condition found for these parameters was 2.16% (wt), 142 °C, 98 min, with 90.51% of the theoretical xylose yield obtained. In a comparison with sulfuric acid hydrolysis, SO2‐catalyzed hydrolysis was proved to be preferable since it resulted in approximately the same sugar yields, but better fermentability. The conversion of xylose to xylitol and volumetric productivity fermented from concentrated SO2‐catalyzed hydrolysate (SCH) were 70.21% and 1.16 g L‐1 h‐1, respectively, higher than those fermented from concentrated sulfuric acid hydrolysate (SAH).CONCLUSIONFindings suggested that the SO2‐catalyzed hydrolysis strategy can be conveniently and effectively applied to xylose and xylitol production. © 2013 Society of Chemical Industry

Effect of selected aldehydes found in the corncob hemicellulose hydrolysate on the growth and xylitol fermentation of Candida tropicalis

The effects of four aldehydes (furfural, 5-hydroxymethylfurfural, vanillin and syringaldehyde), which were found in the corncob hemicellulose hydrolysate, on the growth and xylitol fermentation of Candida tropicalis were investigated. The results showed that vanillin was the most toxic aldehyde for the xylitol fermentation, followed by syringaldehyde, furfural and 5-hydroxymethylfurfural. Moreover, the binary combination tests revealed that furfural amplified the toxicity of other aldehydes and the toxicities of other binary combinations without furfural were simply additive. Based on the fermentation experiments, it was demonstrated that the inhibition of aldehydes could be alleviated by prolonging the fermentation incubation, increasing the initial cell concentration, enhancing the initial pH value and minimizing the furfural levels in the hydrolysate evaporation process. The strategies that we proposed to suppress the inhibitory effects of the aldehydes successfully avoided the complicated and costly detoxifications. Our findings could be potentially adopted for the industrial xylitol fermentation from hydrolysates.

Xylitol fermentation using hemicellulose hydrolysate prepared by acid pre‐impregnated steam explosion of corncob

AbstractBACKGROUNDSteam explosion is widely used on a variety of plant biomass for the hydrolysis of hemicellulose. However, hydrolysis by steam explosion suffers from low xylose yield, long hydrolysis time and high energy consumption, which impede the xylitol fermentation step. This study used a dilute sulfuric acid pre‐impregnation prior to the steam explosion to prepare corncob hemicellulose hydrolysate which offers high xylose yield for xylitol fermentation by Candida tropicalis.RESULTSAfter pre‐impregnation with 0.3% (wt) dilute sulfuric acid at a liquid to corncob ratio of 3 for 6 h, corncobs were steamed at 200 °C for 5 min to obtain a maximum xylose yield of 23.5% in the hydrolysate. The hydrolysate was detoxified by concentrating with vacuum evaporation followed by adsorption using activated carbon. The detoxified hydrolysate was then used for xylitol fermentation. Maximum xylitol yield of 75.1%, volumetric productivity of 2.01 g L‐1 h and biomass of 20.9 g L‐1 were obtained from the detoxified hydrolysate.CONCLUSIONFindings suggested that this acid pre‐impregnated steam explosion strategy provides a highly effective way to prepare hemicellulose hydrolysate with high xylose yield, and could be potentially applied to industrial xylitol fermentation. © 2013 Society of Chemical Industry

Xylitol production from non-detoxified corncob hemicellulose acid hydrolysate by Candida tropicalis

The interest on use of lignocellulose for producing chemicals is increasing as these feedstocks are low cost, renewable and widespread sources of sugars. Corncob is an attractive raw material for xylitol production due to its high content of xylan. In this study, hemicellulose hydrolysate from corncobs without detoxification was used for xylitol production by Candida tropicalis CCTCC M2012462. Compared with prepared xylose medium, xylitol production with dilute acid hydrolysate medium does not seem to influence specific xylose reductase activity. The decrease in xylitol productivity with dilute acid hydrolysate medium is a result of a lower biomass concentration and lag-phase time. It appears that biomass growth rate is essential for xylitol production. In xylitol fermentation with a low initial inhibitors concentration and substrate feeding strategy, a maximal xylitol concentration of 38.8gl−1 was obtained after 84h of fermentation, giving a yield of 0.7gg−1 xylose and a productivity of 0.46gl−1h−1.

Enhanced Production of Xylitol from Corncob by Pachysolen tannophilus Using Response Surface Methodology.

Optimization of the culture medium and process variables for xylitol production using corncob hemicellulose hydrolysate by Pachysolen tannophilus (MTTC 1077) was performed with statistical methodology based on experimental designs. The screening of nine nutrients for their influence on xylitol production was achieved using a Plackett-Burman design. Peptone, xylose, MgSO4·7H2O, and yeast extract were selected based on their positive influence on xylitol production. The selected components were optimized with Box-Behnken design using response surface methodology (RSM). The optimum levels (g/L) were peptone: 6.03, xylose: 10.62, MgSO4·7H2O: 1.39, yeast extract: 4.66. The influence of various process variables on the xylitol production was evaluated. The optimal levels of these variables were quantified by the central composite design using RSM, for establishment of a significant mathematical model with a coefficient determination of R 2 = 0.91. The validation experimental was consistent with the prediction model. The optimum levels of process variables were temperature (36.56°C), pH (7.27), substrate concentration (3.55 g/L), inoculum size (3.69 mL), and agitation speed (194.44 rpm). These conditions were validated experimentally which revealed an enhanced xylitol yield of 0.80 g/g.

Response surface optimization of medium composition for xylitol production by Debaryomyces hansenii var hansenii using corncob hemicellulose hydrolysate

Optimization of the culture medium for xylitol production using Debrayomyces hansenii var hansenii was carried out. The optimization of xylitol production using corncob hemicelluloses hydrolysate as substrate was performed with statistical methodology based on experimental designs. The screening of nine nutrients for their influence of xylitol production to achieved using a Plackett-Burman design. MgSO4.7H2O, KH2PO4, (NH4)2SO4, yeast extract were selected for based on their positive influence on xylitol production. The selected components were optimized using Response Surface Methodology (RSM). The optimum conditions are: MgSO4.7H2O - 1.02 g/l, (NH4)2SO4 - 3.94 g/l, KH2PO4- 2.74 g/l and yeast extract - 3.45 g/l. These conditions are validated experimentally which revealed an enhanced xylitol yield of 0.76 g/g.

Xylitol production from corncob hydrolysate using polyurethane foam with immobilized Candida tropicalis

Polyurethane foam (PUF) was used as a carrier for Candida tropicalis (C. tropicalis) in the multi-batches fermentation of xylitol from xylose-containing corncob hemicellulose hydrolysate. After washing and sterilization, PUF (density of 320kgm−3, specific surface area of 1.5–2.0×105m2m−3, average porosity of 95%, pore diameter of 0.03mm and cubic length of 5mm) was mixed with the culture medium at appropriate proportion followed by the inoculation. The fermentation parameters such as initial cell concentration, PUF dosage, pH value and temperature were controlled to study the effects on xylitol fermentation. In the 21-day durability tests, the optimal xylitol yield and volumetric productivity reached to 71.2% and 2.10gL−1h−1 respectively. Moreover, the average xylitol yield and volumetric productivity were 66.3% and 1.90gL−1h−1 for ten batchwise operations. The current research demonstrated that the PUF immobilization could serve as an efficient method for improving the cells vitality and enzyme reactivity in the continuous operation of fermentation.

Xylitol production by Candida tropicalis from corn cob hemicellulose hydrolysate in a two‐stage fed‐batch fermentation process

AbstractBACKGROUND: Xylitol, a sugar alcohol widely used in food and pharmaceutical industries, can be produced through biological reduction of xylose present in hemicellulose hydrolysates by Candida tropicalis. However, the aeration rate and by‐products originating from hemicellulose hydrolysis strongly inhibit the production of xylitol in a fermentation process. A two‐stage fed‐batch fermentation system was developed to reduce these inhibitory effects and to improve xylitol production from corn cob hemicellulose hydrolysates by C. tropicalis.RESULTS: Results of batch fermentations indicated that high xylitol production could be obtained from C. tropicalis at an initial xylose concentration of 80 g L−1 in corn cob hydrolysate medium at an aeration rate of 0.4 vvm at the micro‐aeration stage. In the two‐stage fed‐batch fermentation process, 96.5 g L−1 xylitol was obtained after 120 h, giving a yield of 0.83 g g−1 and a productivity of 1.01 g L−1 h−1, which were 12.16% and 65.57% higher than those in a batch fermentation.CONCLUSION: High xylitol production can be achieved in a two‐stage fed‐batch fermentation process, in which the negative effects of aeration rate and inhibitory compounds on xylitol formation can be considerably reduced. Copyright © 2011 Society of Chemical Industry

An environmentally friendly and efficient method for xylitol bioconversion with high-temperature-steaming corncob hydrolysate by adapted Candida tropicalis

This study reports a new process to prepare corncob hemicellulose hydrolysate through high temperature steaming (HTS) for xylitol bioconversion by adapted Candida tropicalis. Under the optimal corncob hydrolysis conditions of 160 °C and 120 min, the maximum xylose yield was more than 20%. The optimal fermentative parameters from the HTS hydrolysate is as follows: initial xylose concentration of 140 g l −1, initial pH 6.0, initial cell concentration of 1.2 g l −1 and 30 °C using a two-step dissolved oxygen process with a rotary shaker speed at 200 rpm for the first 24–26 h and then at 150 rpm until 48 h of fermentation. The highest xylitol yield (71.4%) and volumetric productivity (2.12 g l −1 h −1) were obtained from the HTS hydrolysate, which were 158% and 149%, respectively, higher than the results obtained from the acid hydrolysate. Additionally, the amount of inhibitors produced by the HTS hydrolysis and the burden of ion exchange purification after fermentation with HTS hydrolysate were much lower compared with the acid hydrolysate. Therefore, fermentation with corncob HTS hydrolysate is an environmentally friendly and efficient method to produce xylitol, demonstrating a wide potential application in xylitol bioconversion.

Statistical optimization of xylitol production from corncob hemicellulose hydrolysate by Candida tropicalis HDY-02

The statistical experimental designs were adopted to optimize the culture medium in xylitol production by Candida tropicalis HDY-02 with corncob hemicellulose hydrolysate as substrate. In the first step, Plackett-Burman design was used for screening the important variables. KH(2)PO(4), yeast extract, (NH(4))(2)SO(4) and MgSO(4)·7H(2)O were found to significantly affect xylitol yield. In the second step, central composite design (CCD) was used to determine the optimum level of each of the significant variables. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The interactive effects of yeast extract and MgSO(4)·7H(2)O on xylitol yield of C. tropicalis HDY-02 were determined to be significant. The validation experimental was consistent with the prediction model. The optimum combinations for xylitol yield were 5 gl(-1) (NH(4))(2)SO(4), 1.3 gl(-1) KH(2)PO(4), 4.6 gl(-1) yeast extract and 0.6 gl(-1) MgSO(4)·7H(2)O. Under these optimal conditions, the continuous fed-batch experiments could produce xylitol of 58 gl(-1) with a yield of 0.73 g g(-1) xylose.

Integrated production of xylitol and ethanol using corncob

Xylitol production from corncob hemicellulose is a popular process in China. Microbial conversion of xylose to xylitol, as a biological process with many advantages, has drawn increasing attention. As a by-product from the manufacturing of xylitol, corncob cellulosic residues are produced in very large amounts and represent an environmental problem. As a result, considering the large amount of xylitol production in China, the conversion of corncob cellulosic residues has become a widespread issue having to be tackled. After the hemicellulose in corncob has been hydrolyzed for xylitol production, the corncob cellulosic residue is porous and can easily be hydrolyzed by cellulases into glucose and further converted to ethanol, another high-added-value chemical. Based on the latest technology advancements in xylitol, cellulase, and ethanol production, the integrated production of ethanol from corncob cellulosic residues appears as a promising way to improve the profit of the whole xylitol production process.

Maintenance and growth requirements in the metabolism of Debaryomyces hansenii performing xylose‐to‐xylitol bioconversion in corncob hemicellulose hydrolyzate

In order to improve the biotechnological production of xylitol, the metabolism of Debaryomyces hansenii NRRL Y-7426 in corncob hemicellulose hydrolyzate has been investigated under different conditions, where either maintenance or growth requirements predominated. For this purpose, the experimental results of two sets of batch bioconversions carried out alternatively varying the starting xylose concentration in the hydrolyzate (65.6 < or = S(0) < or = 154.7 g L(-1)) or the initial biomass level (3.0 < or = X(0) < or = 54.6 g(DM) L(-1)) were used to fit a metabolic model consisting of carbon material and ATP balances based on five main activities, namely fermentative assimilation of pentoses, semi-aerobic pentose-to-pentitol bioconversion, biomass growth on pentoses, catabolic oxidation of pentoses, and acetic acid and NADH regeneration by the electron transport system. Such an approach allowed separately evaluating the main bioenergetic constants of this microbial system, that is, the specific rates of ATP and xylose consumption due to maintenance (m(ATP) = 21.0 mmol(ATP) C-mol(DM) (-1)h(-1); m(Xyl) = 6.5 C-mmol(Xyl) C-mol(DM) (-1)h(-1)) and the true yields of biomass on ATP (Y(ATP) (max) = 0.83 C-mol(DM) mol(ATP) (-1)) and on xylose (Y(Xyl) (max) = 0.93 C-mol(DM) C-mol(Xyl) (-1)). The results of this study highlighted that the system, at very high S(0) and X(0) values, dramatically increased its energy requirements for cell maintenance, owing to the occurrence of stressing conditions. In particular, for S(0) > 130 g L(-1), these activities required an ATP consumption of about 2.1 mol(ATP) L(-1), that is, a value about seven- to eightfold that observed at low substrate concentration. Such a condition led to an increase in the fraction of ATP addressed to cell maintenance from 47% to 81%. On the other hand, the very high percentage of ATP addressed to maintenance (> 96%) at very high cell concentration (X(0) > or = 25 g(DM) L(-1)) was likely due to the insufficient substrate to sustain the growth.

Effect of Aeration Rate on Production of Xylitol From Corncob Hemicellulose Hydrolysate

The effects of different aeration conditions on xylitol production from corncob hemicellulose hydrolysate by Candida sp. ZU04 were investigated. Batch fermentations were carried out in a 3.7-L fermentor at 30 degrees C, pH 5.5, and agitation of 300 rpm. It was found that the two-phase aeration process was more effective than the one-phase aeration process in xylitol production. In the first 24 h of the aerobic phase, a high aeration rate was applied, glucose was soon consumed, and biomass increased quickly. In the second fermentation phase, aeration rate was reduced and an improved xylitol yield was obtained. The maximum xylitol yield (0.76 g/g) was obtained with an aeration rate of 1.5 vvm (KLa of 37 h-1) for the first 24 h and 0.3 vvm (KLa of 6 h-1) from 24 to 96 h.

Evaluation of xylitol production from corn cob hemicellulose hydrolysate by Candida parapsilosis

Candida parapsilosis was grown for 59 h in a medium containing corn cob hydrolysate consisting of 50 g xylose l−1, 3.0 g glucose l−1, 2.0 g arabinose l−1, and 0.9 g acetic acid l−1. A biomass of 9.1 g l−1 was produced with 36 g xylitol l−1 and 2.5 g ethanol l−1. In a medium containing 50 g xylose l−1 instead of corn cob hydrolysate, the concentrations of cells, xylitol, and ethanol were 8.6 g l−1, 33 g l−1, and 0.2 g l−1, respectively. The differences between two cultures were due to the glucose and arabinose in the corn cob hydrolysate stimulating growth and the low concentration of acetic acid stimulating xylitol production.

Corn Cob Hemicellulose Composition of Corn Isolines Involving Several Mutant Genes1

AbstractAll economically successful xylose production procedures require a carbohydrate source rich in hemicellulose and with a minimum content of other pentose sugars. Mature corn (Zea mays L.) cobs are a good source of hemicellulose. However, birchwood sulphite liquor has been a more economical raw material for xylose production in recent years. A strong pleiotropic or linkage relationship between genes used in today's specialty corn programs and increased hemicellulose content or improved composition would facilitate a program to purchase corn cobs of known genotype. The inbred line Oh43 and its isogenic counterparts homozygous for the recessive endosperm genes wx, su1; du, su2, o2 and ae were tested tor hemicellulose content and composition. The results indicate no relationship between composition of mature cobs and any of the six recessive endosperm genes either in a pleiotropic or linkage sense. Additional visual marker genes should be evaluated so that corn cobs could be used as an economically suitable raw material in a xylose production program.