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1.
Summary The optimal release and quantitative estimation of muramic acid and glucosamine were studied simultaneously in soil samples. The effect of hydrolysis conditions, HCl concentration, hydrolysis time, the ratio of soil dry weight to acid, and the recovery of reference substances were investigated. Derivatization of the fluorogenic reagent o-phthalaldehyde, in the presence of 2-mercaptoethanol with the residue of a soil hydrolysate, was achieved by optimizing the relative amounts of o-phthalaldehyde to hydrolysate in the reaction mixture, the pH of both, and the incubation period. A linear relationship was found between the fluorescence response and the concentration of the test substances. The muramic acid, as well as the glucosamine (o-phthalaldehyde) derivatives gave single peaks, and complete separation from interfering substances at the picomol level was achieved in a short time (3 h preparation and 30 min for chromatography) by using high-performance liquid chromatography.  相似文献   

2.
Chitin and chitosan--value-added products from mushroom waste   总被引：2，自引：0，他引：2  
Accumulation of chitinous material in Agaricus bisporus stalks was determined during postharvest storage at 4 and 25 degrees C. The chitinous material was extracted after alkali treatment and acid reflux of alkali insoluble material and analyzed for yield, purity, degree of acetylation (DA), and crystallinity. The total glucosamine content in mushroom stalks increased from 7.14% dry weight (DW) at harvest (day 0) to 11.00% DW and 19.02% DW after 15 days of storage at 4 degrees C and 5 days of storage at 25 degrees C, respectively. The yield of crude chitin isolated from stalks stored at 25 degrees C for 5 days was 27.00% DW and consisted of 46.08% glucosamine and 20.94% neutral polysaccharides. The DA of fungal chitin was from 75.8 to 87.6%, which is similar to commercially available crustacean chitin. The yield of crude fungal chitin of 0.65-1.15% on a fresh basis indicates the potential for the utilization of these mushroom byproducts.  相似文献   

3.
纤维乙醇工艺中酸处理稻秸秆反应条件的优化   总被引：4，自引：2，他引：2  
以木糖含量为指标,在稀酸处理条件中时间、浓度和液固比影响试验结果的基础上,采用二次回归正交设计优化稀酸处理的条件,建立稀酸处理3因素与木糖含量之间的回归方程关系式,通过验证得到方差分析具有显著性。同时得到各因素的主次因素顺序：时间（x1）＞液固比（x2）＞浓度（x3）。并通过回归方程求解得到的稀酸处理秸秆条的最佳工艺参数为：反应时间2 h,稀酸体积分数4.1%、液固比22︰1,此条件下可以求得较为稳定的木糖质量浓度为0.332 g/L。研究中通过采用二次回归正交设计方法,较大程度地减少了试验次数和优化工艺条件,从而为试验研究提供了一定的依据。此外,该试验研究结果表明3因素交互项对试验结果影响不显著,但反应时间和稀酸浓度2因素的水平选择上有待调整。  相似文献   

4.
On the basis of glycine-dimethyl phosphite synthesis of glyphosate, a new synthesis approach of glyphosate, without using triethylamine and the establishment of triethylamine recovery equipment, was designed in the laboratory. The environmental pollutants were reduced. The influences of reactant amount (mol), reaction temperature (°C), and reaction time (min) on the glyphosate yield and purity were investigated. The results showed that the glyphosate yield and purity could be 80.12 and 86.31 wt %, respectively, under the optimum scheme for glyphosate yield (glycine consumption, 0.1 mol; dimethyl phosphite consumption, 0.12 mol; condensation reaction temperature, 50 °C; hydrochloric acid consumption in hydrolysis reaction, 0.35 mol; temperature of acidification with hydrochloric acid, 10 °C; adjusting hydrolysis product pH value, 1.0; time of dropping esterifying liquid into hydrochloric acid in hydrolysis reaction, 80 min; hydrolysis reaction temperature, 120 °C; and vacuum distillation time, 90 min), and the glyphosate yield and purity could be 77.92 and 94.94 wt %, respectively, under the optimum scheme for glyphosate purity (glycine consumption, 0.1 mol; dimethyl phosphite consumption, 0.1 mol; condensation reaction temperature, 50 °C; hydrochloric acid consumption in hydrolysis reaction, 0.35 mol; temperature of acidification with hydrochloric acid, 10 °C; adjusting hydrolysis product pH value, 1.5; time of dropping esterifying liquid into hydrochloric acid in hydrolysis reaction, 60 min; hydrolysis reaction temperature, 110 °C; and vacuum distillation time, 90 min). The product structures under the two schemes were confirmed by means of FTIR (Fourier transform infrared spectroscopy) and (1)H NMR ((1)H nuclear magnetic resonance spectroscopy).  相似文献   

5.
The ability of immobilized lipase B from Candida antarctica (Novozym 435) to catalyze the direct esterification of glyceryl ferulate (FG) and oleic acid for feruloylated monoacylglycerols (FMAG) preparation in a solvent-free system was investigated. Enzyme screening and the effect of glycerol on the initial reaction rate of esterification were also investigated. Response surface methodology (RSM) was used to optimize the effects of the reaction temperature (55-65 degrees C), the enzyme load (8-14%; relative to the weight of total substrates), oleic acid/(FG + glycerol) (6:1-9:1; w/w), and the reaction time (1-2 h) on the conversion of FG and yield of FMAG. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of FG conversion and FMAG yield. The optimum preparation conditions were as follows: temperature, 60 degrees C; enzyme load, 8.2%; substrate ratio, 8.65:1 (oleic acid/(FG + glycerol), w/w); and reaction time, 1.8 h. Under these conditions, the conversion of FG and yield of FMAG are 96.7 +/- 1.0% and 87.6 +/- 1.2%, respectively.  相似文献   

6.
Determination of glucosamine and N-acetyl glucosamine in fungal cell walls   总被引：1，自引：0，他引：1  
A new method was developed to determine glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc) in materials containing chitin and chitosan, such as fungal cell walls. It is based on two steps of hydrolysis with (i) concentrated sulfuric acid at low temperature and (ii) dilute sulfuric acid at high temperature, followed by one-step degradation with nitrous acid. In this process, chitin and chitosan are converted into anhydromannose and acetic acid. Anhydromannose represents the sum of GlcN and GlcNAc, whereas acetic acid is a marker for GlcNAc only. The method showed recovery of 90.1% of chitin and 85.7-92.4% of chitosan from commercial preparations. Furthermore, alkali insoluble material (AIM) from biomass of three strains of zygomycetes, Rhizopus oryzae, Mucor indicus, and Rhizomucor pusillus, was analyzed by this method. The glucosamine contents of AIM from R. oryzae and M. indicus were almost constant (41.7 +/- 2.2% and 42.0 +/- 1.7%, respectively), while in R. pusillus, it decreased from 40.0 to 30.0% during cultivation from 1 to 6 days. The GlcNAc content of AIM from R. oryzae and R. pusillus increased from 24.9 to 31.0% and from 36.3 to 50.8%, respectively, in 6 days, while it remained almost constant during the cultivation of M. indicus (23.5 +/- 0.8%).  相似文献   

7.
The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, and crystallinity of chitin was investigated. Dry prawn shells were suspended for 4 h in 0.25 M HCl at 40 degrees C while they were sonicated for 0, 1, and 4 h. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH, and sonicated again for 0, 1, and 4 h for protein removal. The yield of chitin decreased from 8.28 to 5.02% for nonsonicated and sonicated samples, respectively, which was attributed to losses of depolymerized materials in the wash water. The application of ultrasound enhanced the removal of proteins. In nontreated shells, the amount of protein was 44.01% and was reduced to 12.55, 10.59, and 7.45% after 0, 1, and 4 h of sonication treatments. The glucosamine content slightly decreased with sonication probably because of losses due to depolymerization. The crystallinity indices of chitins decreased as the time of sonication increased. The degree of acetylation of chitins was unaffected by sonication, but the degree of acetylation of chitosans produced from sonicated chitin decreased from 70.0 to 68.7 and 61.4% for 1 and 4 h sonicated samples, respectively.  相似文献   

8.
One-step hydrolysis of chitin to release glucosamine for quantitation was achieved by combining a chitin-containing sample (10-200 mg of sample size) in a test tube with 1 mL of 10 M HCl followed by vacuum treatment for 10 min, incubation at 28 degrees C for 30 min, replenishment with 3 mL of deionized water, nitrogen flushing, screw capping, and heat treatment at 140 degrees C for 60 min. A phosphate buffer solution (pH 12.5, 0.2 M) was effective in pH stabilization and enhancing colorimetric determination of glucosamine content. When the modified procedure was applied to analyze glucosamine content in the mycelia of various molds, glucosamine content varied mainly depending on mold species. In estimations of mold growth of the uninoculated peanut kernels incubated under a humidified condition for 5 weeks, cooked rice and soybean inoculated with conidia of Aspergillus oryzae for koji preparation, logarithms of the internal mold populations and glucosamine contents both increased with increases of incubation time. The modified procedure provided a rapid and reliable estimation of mold growth in various substrates.  相似文献   

9.
Deacetylation of chitin under autoclaving conditions (15 psi/121 degrees C) was evaluated for the preparation of chitosan under different NaOH concentrations and reaction times. Deacetylation was effectively achieved by treatment of chitin under elevated temperature and pressure with 45% NaOH for 30 min and a solids/solvent ratio of 1:15. Treated chitosan showed similar nitrogen content (7.42%), degree of deacetylation (90.4%), and molecular mass (1560 kDa) but significantly higher viscosity values (2025 cP) compared with those (7.40%, 87.6%, 1304 kDa, and 143 cP, respectively) of a commercial chitosan. Reduction of the solids/solvent ratio from 1:15 to 1:10 did not affect degree of deacetylation, viscosity, and molecular mass of chitosan.  相似文献   

10.
The influence of sonication during extraction of chitin from North Atlantic shrimp (NAS) shells (Pandalus borealis) on chitin yield, purity, and crystallinity was investigated. Shells were peeled, washed, lyophilized, ground, and suspended for 4 h in 0.25 M HCl (1:40) at 40 degrees C followed by ultrasonication at 41 W/cm(2) for 0, 1, and 4 h, respectively. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH (1:40), and ultrasonicated at 41 W/cm(2) for 0, 1, and 4 h to remove proteins. The yield and mineral and protein contents were determined after each processing step. The purity of extracted chitin was determined from the total amount of glucosamine. The crystallinity index and size of crystals were calculated from wide-angle X-ray scattering measurements. Scanning electron microscope images were recorded to evaluate morphological changes in samples. The yield of chitin from NAS decreased from 16.5 to 11.4% for 0 and 1 h sonicated samples, respectively, which was attributed to increased concentrations of depolymerized materials in the wash water. Sonication did not enhance the removal of minerals. The application of ultrasound enhanced the removal of proteins from 39.8 to 10.6, 8.3, and 7.3% after 0, 1, and 4 h of sonication treatments. The crystallinity index of chitin decreased from 87.6 to 79.1 and 78.5% after 1 and 4 h of sonication, yielding chitosans with crystallinity indices of 76.7, 79.5, and 74.8% after deacetylation, respectively. Fourier transform infrared spectroscopy scans indicated that the degree of acetylation of chitins was unaffected by sonication. Comparison of the extraction results of NAS with that from freshwater prawns indicated that more impurities were left in NAS chitin, suggesting that composition and structural arrangement of chitin in shells influence the efficiency of ultrasound-assisted extraction.  相似文献   

11.
超声波辅助高氯酸法提取牛肝中左旋肉碱工艺优化   总被引：2，自引：0，他引：2  
孙娜  余群力  曹晖 《农业工程学报》2012,28(21):280-286
为探索超声波处理对左旋肉碱提取效果的影响,找出最佳的处理技术参数,以牛肝脏为原料,用超声波辅助酸提法提取左旋肉碱,在超声功率、超声时间和料液比3个单因素试验的基础上,采用二次回归通用旋转组合试验设计对左旋肉碱超声波辅助提取工艺进行优化。结果表明,试验中所选参试因子对左旋肉碱提取得率的影响大小顺序为超声波功率、料液比、超声时间。最优工艺条件为:原料用量为100g,在超声功率437W,超声时间15min,料液比1∶5g/mL时,左旋肉碱提取得率达38.37mg/kg。该研究表明超声波技术在左旋肉碱提取工艺中具有较高的应用价值和指导作用。  相似文献   

12.
The reaction of L-tryptophan (Trp) with D-glucose under conditions that can occur during food processing and preparation was studied by high-performance liquid chromatography with diode array detection (HPLC/DAD). Besides the well-established glucose-tryptophan Amadori product (AP), (1R,3S)-1-(D-gluco-1,2,3,4,5-pentahydroxypentyl)-1,2,3, 4-tetrahydro-beta-carboline-3-carboxylic acid (PHP-THbetaC) was identified as an important product of this reaction. For preparation, PHP-THbetaC was obtained in high yields when Trp and D-glucose were reacted under strongly acidic conditions after heating in methanol. At elevated reaction temperatures (150 degrees C) 1-acetyl-beta-carboline (acetyl-betaC), was detected in significant concentrations. The mixtures were heated under variations of reaction time and temperature, and AP, PHP-THbetaC, and acetyl-betaC were quantified. In the presence of air oxygen or mild, food relevant oxidants, such as L-dehydroascorbic acid, PHP-THbetaC was readily oxidized to a product that was identified as the previously unknown 1-(D-gluco-1,2,3,4,5-pentahydroxypentyl)-beta-carboline (PHP-betaC). Formation of PHP-THbetaC and PHP-betaC in foodstuffs would deserve particular interest because multiple physiological activity of THbetaC and betaC derivatives has been shown previously.  相似文献   

13.
Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation, and crystallinity and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in the mycelium of A. niger was 11.10% dw and in the mycelium of M. rouxii was 20.13% dw. On the basis of the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan, whereas A. niger contained only chitin. The yields of crude chitin from A. niger and M. rouxii were 24.01 and 13.25%, respectively, and the yield of chitosan from M. rouxii was 12.49%. Significant amounts (7.42-39.81%) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degrees of acetylation were determined to be 76.53 and 50.07% for chitin from A. niger and M. rouxii, respectively, and 19.5% for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intense than in corresponding materials from shrimp shells. The extracted chitin and chitosan in a concentration of 0.1% reduced Salmonella Typhimurium DT104 2576 counts by 0.5-1.5 logs during a 4 day incubation in tryptic soy broth at 25 degrees C. Furthermore, all tested chitinous materials from fungal sources significantly reduced lesions caused by Botrytis cinerea and Penicillium expansum in harvested apples.  相似文献   

14.
Response surface methodology was successfully employed to optimize lipase-catalyzed synthesis of feruloyl butyryl glycerides (FBGs). The effects of the reaction parameters, including the reaction time, reaction temperature, enzyme concentration, substrate molar ratio, and water activity, and the interaction parameters were examined. The analysis suggested that the conversion of the FBGs was significantly (p < 0.05) affected by independent factors of reaction time, reaction temperature, substrate molar ratio, and water activity as well as interactive terms of reaction temperature/reaction time, reaction temperature/enzyme concentration, substrate molar ratio/reaction temperature, water activity/reaction temperature, reaction time/enzyme concentration, and enzyme concentration/water activity. The highest conversion yield of FBGs was 81.2% at the following optimized reaction conditions: reaction temperature of 53.6 degrees C, reaction time of 5.5 days, enzyme concentration of 50.8 mg/mL, water activity of 0.14, and substrate molar ratio of 2.9. The conversion is higher as compared to that at the conditions before optimization.  相似文献   

15.
响应面法优化酸水解稻秆制木糖的工艺参数   总被引：8，自引：4，他引：4  
为了提高稀硫酸水解稻秆制木糖的收率,采用响应面法对稀硫酸水解稻秆制木糖的关键参数进行了优化研究,建立了木糖收率的二次多项式数学模型,并分析模型的有效性与因子间的交互作用。结果表明,3个因素对木糖收率的影响大小依次为酸浓度（质量分数）＞温度＞时间;稀硫酸水解稻秆制木糖的最佳工艺参数为：酸质量分数1.52%、温度121℃和时间为56 min。在此条件下,木糖的最高收率为78.12%。在最佳工艺条件下得到实验结果与模型预测值很吻合,说明所建立的模型是切实可行的。  相似文献   

16.
Kinetics and products of the degradation of chitosan by hydrogen peroxide   总被引：8，自引：0，他引：8  
Low concentrations of hydrogen peroxide induced random degradation of partially deacetylated chitin and chitosan. Average molecular weight decreased in accordance with first-order kinetics. The degradation rate was much faster than that of the ultrasonic degradation, and it was comparable to that of the enzymatic hydrolysis of chitosan. Chain-end scissions occurred after chitosan was degraded severely and produced significant amounts of oligosaccharides at temperatures > or =80 degrees C. Universal calibration moderated the change in molecular weight more closely than that calculated by the usual calibration using pullulan standards. Trace amounts of transition metal ions and the amino groups in chitosan were critical to the breakdown of the beta-1,4 glycosidic linkages. HPLC results of glucosamine and chito-oligosaccharides could be characterized by correlating the logarithmic values of retention time with the degrees of polymerization. The formation of glucosamine and chito-oligosaccharides depended on the concentration of H(2)O(2), temperature, and the physicochemical property of chitin/chitosan.  相似文献   

17.
Human milk fat substitutes (HMFSs) were synthesized by lipozyme RM IM-catalyzed acidolysis of chemically interesterified palm stearin (mp = 58 °C) with mixed FAs from rapeseed oil, sunflower oil, palm kernel oil, stearic acid, and myristic acid in a solvent-free system. Response surface methodology (RSM) was used to model and optimize the reactions, and the factors chosen were reaction time, temperature, substrate molar ratio, and enzyme load. The optimal conditions generated from the models were as follows: reaction time, 3.4 h; temperature, 57 °C; substrate molar ratio, 14.6 mol/mol; and enzyme load, 10.7 wt % (by the weight of total substrates). Under these conditions, the contents of palmitic acid (PA) and PA at sn-2 position (sn-2 PA) were 29.7 and 62.8%, respectively, and other observed FAs were all within the range of FAs of HMF. The product was evaluated by the cited model, and a high score (85.8) was obtained, which indicated a high degree of similarity of the product to HMF.  相似文献   

18.
Miscanthus giganteus lignin was extracted by an organosolv process under reflux conditions (4 h) with varying concentrations of ethanol (65%, 75%, 85%, 95%) and 0.2 M hydrochloric acid as catalyst. The resulting lignin was extensively characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR), and chemical analysis (residual sugars, Klason lignin, ash). The predominant linkage units present were β-O-4' (82-84%), resinol (6-7%), and phenylcoumaran (10-11%). The 65% ethanol solvent system gave the lowest lignin yield (14% of starting biomass) compared to 29-32% of the other systems. Increasing ethanol concentration resulted in decreasing carbohydrate content of the lignins (3.6-1.1%), a higher solubility in tetrahydrofuran (THF), a slight reduction of the molecular weight (M(w) 2.72-2.25 KDa), an increasing α-ethoxylation, and an increase in ethoxylated phenylpropenoic compounds (p-coumaric and ferulic acid), but the S/G ratio of the monolignols (0.63, GC/MS) and Klason lignin content (86-88%) were unaffected. An extraction method for these ethyl-esterified phenylpropenoids and smaller molecular weight lignin compounds was developed. The effect of reaction time (2, 4, and 8 h) was investigated for the 95% ethanol solvent system. Besides increased lignin yield (13-43%), a slight increase in M(w) (2.21-2.38 kDa) and S/G ratio (0.53-0.68, GC-MS) was observed. Consecutive extractions suggested that these changes were not from lignin modifications (e.g., condensations) but rather from extraction of lignin of different composition. The results were compared to similar solvent systems with 95% acetone and 95% dioxane.  相似文献   

19.
碳基固体酸催化高酸值生物柴油原料降酸效果   总被引：5，自引：1，他引：4  
以淀粉和对甲苯磺酸合成的碳基固体酸为催化剂,油酸模拟高酸值生物柴油原料进行酯化降酸的试验研究,考察醇油比、催化剂用量、反应温度、反应时间及重复利用性等因素对转化率的影响。通过单因素与正交试验确定最佳工艺条件：醇油质量比为1︰4,催化剂用量为油酸质量的6.5%,反应时间6 h,反应温度85℃,在此条件下转化率可达80.21%,重复使用6次,转化率仍保持在70%以上。碳基固体酸催化剂对高酸值原料酯化降酸有很好的催化活性,易于分离且具有良好的稳定性。  相似文献   

20.
小球藻粉水热催化液化制备生物油   总被引：2，自引：3，他引：2  
为探索新型生物质燃油的开发,该文以小球藻粉为原料,采用水热催化液化方法制备生物油。研究了液化温度,液化时间,催化剂等因素对液化率的影响,在此基础上采用正交试验,以液化率为指标,探讨了生物油优化的制备工艺;利用傅里叶红外光谱(FTIR)和气相色谱-质谱联用(GC/MS)技术分析了小球藻粉生物油的基团结构与组成。结果表明,小球藻粉优化的液化反应条件为:采用质量分数5%的Ce/HZSM-5为催化剂,在300°C水热条件下催化液化20min,小球藻粉和溶剂料液比为1:10g/mL,液化率达39.87%。在此条件下制备的小球藻粉生物油的主要成分为醇类,酯类以及部分碳氢化合物,热值达26.09MJ/kg。和传统木质纤维素类生物质相比,小球藻粉制备的生物油成分更接近传统化石燃油且热值更高,显示了良好的应用前景,为微藻生物质液体燃料的制备提供参考。  相似文献   

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