Microwave promoted methylation of plant polysaccharides

O-Methylation is of outstanding importance in structural polysaccharide chemistry. A novel method for the methylation of polysaccharides using microwave (MW) irradiation is described. Seed gum from Cyamopsis tetragonolobus (Guar) was fully methylated with dimethyl sulphate and sodium hydroxide using 100% microwave power for 4 min in 68% yield. The completely methylated seed gum thus obtained was hydrolyzed by 70% formic acid followed by 0.5N H₂SO₄ under full microwave power for 1.16 and 1.66 min, respectively. The partially methylated monosaccharides were separated and identified.     

Synthesis and characterization of guar gum‐graft‐polyacrylonitrile

Cerium(IV) mediated grafting of polyacrylonitrile on to guar gum was studied. Grafting parameters were studied gravimetrically, as a function of temperature, initiator concentration and Guar to acrylonitrile ratio. Higher temperatures resulted in higher monomer conversion and homopolymer formation. Both monomer conversion and extent of grafting increased with increase in cerium ion concentration in the range studied (0.91–9.12 mmol/l). Similar results were obtained with increase in monomer to guar gum ratio from 1 to 5. Grafting with this initiator was found to be generally good with high grafting efficiencies and low homopolymer formation for most experiments. The copolymers obtained were subjected to alkaline hydrolysis to convert nitrile groups in to carboxylic acid groups and the water absorbency of the resulting anionic guar gum was studied. Materials with water absorption up to 300 g/g could be obtained from this study. Copyright © 2003 John Wiley & Sons, Ltd.     

两性田菁胶在处理生活污水中的助凝作用

研究了以聚合硫酸铁为主凝剂、两性田菁胶(ASG)为助凝剂处理城市生活废水的各种影响因素.实验结果表明:聚合硫酸铁和两性田菁胶分别以200mg/L和10mg/L的复配浓度、pH值接近7时混凝效果最佳,CODCr去除率达到近80%,处理后废水CODCr达到国家排放标准.     

Improvement of the electrophoretic protein profiles of Leguminosae gums extracts using gamanase and application to the evaluation of carob-guar mixtures

A quantitative assay for guar gum in carob gum, based on the extraction of proteins in acetonitrile-water (7:3), separation by capillary electrophoresis and multiple linear regression (MLR) using the areas of nine selected peaks as predictors, was improved by performing the extraction in the presence of gamanase. In the absence of the enzyme, peak migration times and areas depended on the guar content, which complicated peak identification and evaluation. Manual correction of the migration times by comparison with standard electropherograms obtained with pure carob and carob-guar mixtures was required; however, when the proteins were extracted under sonication at 60 °C for 30 min in the presence of gamanase, the migration times and peak areas did not vary with the composition of the carob-guar mixtures, and its reproducibility improved largely. These effects were attributed to the reduction of the viscosity of the extracts and the removal of the galactomannose interactions with the proteins and the capillary walls. Peak identification and evaluation were easily and directly performed on these electropherograms without further processing. An MLR model constructed with 36 carob-guar mixtures containing up to 20% guar, and by measuring the areas of 12 selected peaks and using eight of them as predictors, yielded a detection limit of 2.8% guar (α=β=0.05 criterion). A model of similar quality was obtained by partial least-squares (PLS) regression.     

Superoxes,high temperature universal phases in (GC)2

Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ～50° to ～300°. High MW Superox-4 has a MAOT about 20° higher than the lower MW Superox-0.1. Several applications illustrating the versatility of Superox phases in (GC)² are presented.     

Graft copolymerisation of acrylamide onto cashew gum

The synthesis of cashew gum-g-polyacrylamide was carried out at 60 °C by a radical polymerisation using potassium persulphate as the redox initiator under N₂ atmosphere. A series of graft copolymers, varying in acrylamide concentration and keeping the concentration of the initiator and polysaccharide constant, was prepared. These graft copolymers were characterised by elemental analysis, infrared and ¹³C NMR spectroscopy, rheological studies, differential scanning calorimetry and thermogravimetric analysis. Comparisons amongst grafting parameters of the reaction of various natural polysaccharides with polyacrylamide (PAM) were carried out. High percentages of acrylamide conversion (%C) and grafting efficiency (%E) were obtained for cashew gum (CG), even with a low acrylamide/gum ratio. All copolymers had intrinsic viscosity and thus the hydrodynamic volume much higher than the CG value and closer to the PAM. The CG-g-PAM solution had an absolute viscosity at 2.5% concentration (wt./vol.) up to 33 and 3.3 times the CG and PAM values, respectively. Grafting of PAM chains onto the polysaccharide enhances its thermal stability.     

Effect of environmental factors and carbohydrate on gellan gum production

Submerged culture fermentation studies were carried out in batch mode for optimizing the environmental parameters and carbon source requirement by Pseudomonas elodea for the production of gellan gum. The maximum production of gellan gum was obtained with 16-h-old culture and 8% inoculum at 30°C and pH 7.0 after 52 h of incubation (6.0 g/L). Of the various carbon sources tested, 2% sucrose, glucose, and soluble starch yielded considerably high amounts of gellan. Studies on the concentration of various carbohydrates on gellan gum production indicated that the optimum concentration of glucose and starch was 3%, whereas for sucrose it was 4%. The addition of glucose in the medium above 3% had a detrimental effect on gellan yield. The investigation of intermediate two-step addition of glucose under identical conditions of fermentation showed an enhanced production of gellan (8.12 g/L) as compared with the control (6.0 g/L). To optimize the recovery of gellan from fermented broth, different solvents were tested for precipitation of gellan gum. Among the various solvents tested, tetrahydrofuran gave better recovery of gellan (82%) as compared with the conventional solvent isopropanol (49%).     

Effect of surface attachment on synthesis of bacterial cellulose

Gluconacetobacter spp. synthesize a pure form of hydrophilic cellulose that has several industrial specialty applications. Literature reports have concentrated on intensive investigation of static and agitated culture in liquid media containing high nutrient concentrations optimized for maximal cellulose production rates. The behavior of these bacteria on semisolid and solid surfaces has not been specifically addressed. The species Gluconacetobacter hansenii was examined for cellulose synthesis and colony morphology on a range of solid supports, including cotton linters, and on media thickened with agar, methyl cellulose, or gellan. The concentration and chemical structure of the thickening agent were found to be directly related to the formation of contiguous cellulose pellicules. Viability of the bacteria following freezer storage was improved when the bacteria were frozen in their cellulose pellicules. This article was authored by a contractor of the US government under contract no. DEAC05-00OR22725. Accordingly, the US government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US government purposes.     

Effect of polymer and ion concentration on mechanical and drug release behavior of gellan hydrogels using factorial design

Developing optimized hydrogel products requires an in-depth understanding of the mechanisms that drive hydrogel tunability. Here, we performed a full 4 × 4 factorial design study investigating the impact of gellan, a naturally derived polysaccharide (1%, 2%, 3%, or 4% w/v) and CaCl₂ concentration (1, 3, 7, or 10 mM) on the viscoelastic, swelling, and drug release behavior of gellan hydrogels containing a model drug, vancomycin. These concentrations were chosen to specifically provide insight into gellan hydrogel behavior for formulations utilizing polymer and salt concentrations expanding beyond those commonly reported by previous studies exploring gellan. With increasing gellan and CaCl₂ concentration, the hydrogel storage moduli (0.1–100 kPa) followed a power-law relationship and on average these hydrogels had higher liquid absorption capability and greater total drug release over 6 days. We suggest that the effects of gellan and CaCl₂ concentration and their interactions on hydrogel properties can be explained by various phenomena that lead to increased swelling and increased resistance to network expansion.     

Synthesis of guar gum-based hydrogel for sugarcane field solid conditioning

The water crisis is increased everywhere in recent years, which has affected the water demand in different sectors like industries, agriculture, residential, etc. The present research aims to the development of superabsorbent polymer (SAP) using bio-material. The hydrogel is synthesized by grafting Guar gum (GG) with methyl methacrylate (MMA) and crosslinking with polyethylene glycol (PEG). The developed GG-based hydrogelwas characterized by various analytical instruments. The Scanning Electron Microscopy (SEM) demonstrated hydrogels havepores of size 50 ​μm–10 ​μm. The Transmission Electron Microscopy (TEM) analysis has shownthat thematerial consists of spherical shapesand particles of size 141.11nm–182.19 ​nm.The Fourier-Transform Infrared Spectroscopy (FTIR) and Thermogravimetric analysis (TGA) study have confirmedthepresence of functional groups of material, and thermal resistivity. The absorption capacity of developed hydrogelwas found to be 110 ​ml per gram (110% of its dry weight). The hydrogelwasapplied in the field of sugarcane crop and measured soil moisture content after 20 days of application. A better resultwas found of moisture content in the area of hydrogel application (28%) compared to the area without hydrogel application (10%). Moreover, the comparison of different hydrogels is also shown in a study, and the developed hydrogel proves good moisture retention capacity. This technology could be promising in terms of improving perennial crop productivity and combating moisture stress in agriculture. As a soil conditioning material for agricultural applications, the synthesized hydrogel showed tremendous potential.