Preparation and characterization of poly(acrylic acid)-hydroxyethyl cellulose graft copolymer

Poly(acrylic acid) hydroxyethyl cellulose [poly(AA)-HEC] graft copolymer was prepared by polymerizing acrylic acid (AA) with hydroxyethyl cellulose (HEC) using potassium bromate/thiourea dioxide (KBrO(3)/TUD) as redox initiation system. The polymerization reaction was carried out under a variety of conditions including concentrations of AA, KBrO(3) and TUD, material to liquor ratio and polymerization temperature. The polymerization reaction was monitored by withdrawing samples from the reaction medium and measuring the total conversion. The rheological properties of the poly(AA)-HEC graft copolymer were investigated. The total conversion and rheological properties of the graft copolymer depended on the ratio of KBrO(3) to TUD and on acrylic acid concentration as well as temperature and material to liquor ratio. Optimum conditions of the graft copolymer preparation were 30mmol KBrO(3) and 30mmol TUD/100g HEC, 100% AA (based on weight of HEC), duration 2h at temperature 50°C using a material to liquor ratio of 1:10.     

Production of lactic acid from paper sludge using acid-tolerant, thermophilic Bacillus coagulan strains

Production of lactic acid from paper sludge was studied using thermophilic Bacillus coagulan strains 36D1 and P4-102B. More than 80% of lactic acid yield and more than 87% of cellulose conversion were achieved using both strains without any pH control due to the buffering effect of CaCO₃ in paper sludge. The addition of CaCO₃ as the buffering reagent in rich medium increased lactic acid yield but had little effect on cellulose conversion; when lean medium was utilized, the addition of CaCO₃ had little effect on either cellulose conversion or lactic acid yield. Lowering the fermentation temperature lowered lactic acid yield but increased cellulose conversion. Semi-continuous simultaneous saccharification and co-fermentation (SSCF) using medium containing 100 g/L cellulose equivalent paper sludge without pH control was carried out in serum bottles for up to 1000 h. When rich medium was utilized, the average lactic acid concentrations in steady state for strains 36D1 and P4-102B were 92 g/L and 91.7 g/L, respectively, and lactic acid yields were 77% and 78%. The average lactic acid concentrations produced using semi-continuous SSCF with lean medium were 77.5 g/L and 77.0 g/L for strains 36D1 and P4-102B, respectively, and lactic acid yields were 72% and 75%. The productivities at steady state were 0.96 g/L/h and 0.82 g/L/h for both strains in rich medium and lean medium, respectively. Our data support that B. coagulan strains 36D1 and P4-102B are promising for converting paper sludge to lactic acid via SSCF.     

Determining the Polymer Threshold Amount for Achieving Robust Drug Release from HPMC and HPC Matrix Tablets Containing a High-Dose BCS Class I Model Drug: In Vitro and In Vivo Studies

It is challenging to achieve mechanically robust drug-release profiles from hydrophilic matrices containing a high dose of a drug with good solubility. However, a mechanically robust drug release over prolonged period of time can be achieved, especially if the viscosity and amount of the polymer is sufficiently high, above the “threshold values.” The goal of this research was to determine the hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) polymer threshold amount that would enable robust drug release from matrix tablets containing a high dose of levetiracetam as a class I model drug according to the Biopharmaceutical Classification System (BCS). For this purpose, formulations containing HPC or HPMC of similar viscosity range, but in different amounts, were prepared. Based on the dissolution results, two final formulations were selected for additional in vitro and in vivo evaluation to confirm the robustness and to show bioequivalence. Tablets were exposed to various stress conditions in vitro with the use of different mechanically stress-inducing dissolution methods. The in vitro results were compared with in vivo results obtained from fasted and fed bioequivalence studies. Under both conditions, the formulations were bioequivalent and food had a negligible influence on the pharmacokinetic parameters C_max and area under the curve (AUC). It was concluded that the drug release from both selected formulations is mechanically robust and that HPC and HPMC polymers with intrinsic viscosities above 9 dL/g and in quantities above 30% enable good mechanical resistance, which ensures bioequivalence. In addition, HPC matrices were found to be more mechanically robust compared to HPMC.KEY WORDS: HPC, HPMC, matrix tablets, mechanically robust dissolution, threshold amount     

Production of D(-)-lactic acid from cellulose by simultaneous saccharification and fermentation using Lactobacillus coryniformis subsp. torquens

D(–)-Lactic acid was produced from cellulose by simultaneous saccharification and fermentation (SSF) in media containing cellulolytic enzymes and Lactobacillus coryniformis subsp. torquens ATCC 25600 at 39 °C and pH 5.4, yielding 0.89 g D(–)-lactic acid g^–1 cellulose at a mean volumetric productivity of 0.5 g l^–1 h^–1. No L(+)-lactic acid was found in the medium.     

Utilization of hydroxypropyl cellulose and poly(acrylic acid)-hydroxypropyl cellulose composite as thickeners for textile printing

Trials were carried out to partially replace kerosene oil with hydroxypropyl cellulose (HPC), poly(acrylic acid)-hydroxypropyl cellulose composite (poly (AA)-HPC) and their mixture in pigment printing paste. Partial replacement was carried out under a variety of conditions. Variables studied include type and concentration of the aqueous thickening agent and type of pigment dyes. In addition to that, poly (AA)-HPC composite was tried to replace sodium alginate in reactive printing. The fastness properties, color strength and stiffness were measured for the reactive and pigment printed samples.     

l-Dopa synthesis using tyrosinase immobilized on magnetic beads

Magnetic beads were prepared via suspension polymerization of glycidyl methacrylate (GMA) and methyl methacrylate (MMA) in the presence of ferric ions. Following polymerization, thermal co-precipitation of the Fe(III) ions in the beads with Fe(II) ions under alkaline condition resulted in encapsulation of Fe₃O₄ nano-crystals within the polymer matrix. The magnetic beads were activated with glutaraldehyde, and tyrosinase enzyme was covalently immobilized on the support via reaction of amino groups under mild conditions. The immobilized enzyme was used for the synthesis of l-Dopa (1-3,4-dihydroxy phenylalanine) which is a precursor of dopamine. The immobilized enzyme was characterized by temperature, pH, operational and storage stability experiments. Kinetic parameters, maximum velocity of the enzyme (V_max) and Michaelis–Menten constant (K_m) values were determined as 1.05 U/mg protein and 1.0 mM for 50–75 μm and 2.00 U/mg protein and 4.0 mM for 75–150 μm beads fractions, respectively. Efficiency factor and catalytic efficiency were found to be 1.39 and 0.91 for 75–150 μm beads and 0.73 and 0.75 for 50–75 μm beads fractions, respectively. The catalytic efficiency of the soluble tyrosinase was 0.37. The amounts of immobilized protein were on the 50–75 μm and 75–150 μm fractions were 2.7 and 2.8 mg protein/g magnetic beads, respectively.     

Selective production of bikaverin in a fluidized bioreactor with immobilized Gibberella fujikuroi

The best culture medium composition for the production of bikaverin by Gibberella fujikuroi in shake-flasks, i.e. 100 g glucose l^–1; 1 g NH₄Cl l^–1; 2 g rice flour l^–1; 5 g KH₂PO₄ l^–1 and 2.5 g MgSO₄ l^–1, was obtained through a fractional factorial design and then scaled-up to a fluidized bioreactor. The effects of carbon and nitrogen concentrations, inoculum size, aeration, flow rate and bead sizes on batch bikaverin production using immobilized G. fujikuroi in a fluidized bioreactor were determined by an orthogonal experimental design. Concentrations of up to 6.83 g bikaverin l^–1 were obtained when the medium contained 100 g glucose l^–1 and 1 g NH₄Cl l^–1 with an inoculum ratio of 10% v/v, an aeration rate of 3 volumes of air per volume of medium min^–1, and a bead size of 3 mm. Based on dry weight, the bikaverin production was 30–100 times larger than found in submerged culture and approximately three times larger than reported for solid substrate fermentation.     

Acid hydrolysis of sunflower seed husks for production of single cell protein

Summary Sunflower seed husks were chosen as a typical lignocellulosic waste product of low value. This model substrate was hydrolyzed with sulphuric acid at 120°C. The hydrolysis was carried out in two steps: hydrolysis of the pentosan fraction and subsequent hydrolysis of the cellulose fraction. The pentosan fraction was nearly quantitatively hydrolyzed. For the cellulose hydrolysis the yield was 79% of the theoretical yield. The hydrolyzates were neutralized to pH 5 with solid calcium hydroxide and used for preparation of growth media forCandida yeasts andPaecilomyces variotii. For the pentosan hydrolyzates the yields of yeast biomass were 35–36 g per 100 g available reducing sugars (supplied to the medium). In cellulose hydrolyzates the corresponding yields were 45–48 g withCandida utilis andC. tropicalis and about 30 g withC. pseudotropicalis. P. variotii was noticeably superior to the yeasts. In pentosan hydrolyzates it produced 63 g dry mycelium from 100 g reducing sugars supplied; in cellulose hydrolyzates, 94 g. This suggests that it must be an effective utilizer of a wide range of compounds, for example, organic acids in the medium.     

Molecular dynamic studies of the compatibility of some cellulose derivatives with selected ionic liquids

Molecular dynamics techniques were used to study oligomers that mimic cellulose and various derivatives in the amorphous phase, including cellulose (C), methyl cellulose (MC), hydroxypropyl cellulose (HPC), and carboxymethyl cellulose (CMC). Densities and solubility parameters were determined for a series of oligomers with increasing chain length. Both properties were found to change linearly with the degree of polymerization (from monomers to dodecamers). Extrapolated predictions of the densities (g/cm³) for long chain polymers are: C, 1.42; MC, 1.33; HPC, 1.30; and CMC, 1.42. Computed values for the solubility parameter (MPa^1/2) are: C, 25.39; MC, 21.43; HPC, 21.70; and CMC, 24.35. We also evaluated the sensitivity of the solubility parameter to changes in the calculated density and found the dependence to be significant. The calculated solubility parameters were evaluated against experimental and other theoretical values as well as against selected ionic liquids comprised of cations in the imidazolium family and the chloride and trifluoroacetate anions.     

Selection of transgenic flax plants is facilitated by spectinomycin

Regeneration of transformed flax shoots after inoculation withAgrobacterium tumefaciens carrying a binary vector with either a neomycin phosphotransferase (nptII) gene and a -glucuronidase (GUS) reporter gene or a spectinomycin resistance gene was examined. Hypocotyls from 4-day-old seedlings were inoculated with either of the twoA. tumefaciens strains. Selection and regeneration were achieved on a medium containing 0.1 M thidiazuron, 0.01 M napthalene acetic acid, 100 mgl^–1 kanamycin sulphate or spectinomycin sulphate and 300 mgl^–1 cefotaxime. Use of different neomycins for the selection of transformed tissues did select transformed calli but not transformed shoots either directly or via a callus phase. Selection based on spectinomycin resistance allowed the growth of transformed shoots. Transgenic shoots were rooted on a medium containing 100 mgl^–1 spectinomycin sulphate. Integration of the spectinomycin resistance gene into the flax genome was confirmed by Southern blot hybridizations and spectinomycin resistance was shown to be inherited as a dominant Mendeliant trait. Therefore, spectinomycin resistance is more suitable for genetic engineering of flax than aminoglycoside resistance.     

Multiple Shoot Induction from Cotyledonary Node Explants of Terminalia chebula

A protocol for multiple shoot induction from cotyledonary node explants of Terminalia chebula Retz. has been developed. Germination frequency of embryos (up to 100 %) was obtained on Murashige and Skoog (MS) medium supplemented with 0.5 mg dm^–3 gibberellic acid (GA₃). Maximum number of shoots (6.4 shoots per cotyledonary node) was obtained on half-strength MS + 0.3 mg dm^–3 GA₃+ 1.0 mg dm^–3 indole-3-butyric acid (IBA) + 10.0 mg dm^–3 benzylaminopurine (BAP) after 4 weeks of culture. When the cotyledonary nodes along with the axillary shoot buds were allowed to grow in the same medium upto 19.2 shoots were obtained after 8 – 9 weeks. Best rooting (100 %, 5.5 roots per shoot) was observed when shoots were excised and transferred to half-strength MS medium containing 1.0 mg dm^–3 IBA + 1 % mannitol and 1.5 % sucrose. Survival of rooted plants in vivo was low (35 – 40 %) when they were directly transferred to soil in glasshouse. However, transfer to soil with MS nutrients and 1.0 mg dm^–3 IBA in culture room for a minimum duration of 2 weeks increased the survival percentage of plants to 100 %.     

Cutinase purification on poly(ethylene glycol)–hydroxypropyl starch aqueous two-phase systems

The partition behaviour of cutinase on poly(ethylene glycol) (PEG)–hydroxypropyl starch aqueous two-phase systems was characterized. The effect of molecular mass of PEG, the pH of the system and tie-line length on cutinase partition coefficient and cutinase yield to the top phase was investigated for systems prepared with a purified hydroxypropyl starch (Reppal PES 100) and a crude one (HPS). The effect of the presence of different salts, such as sodium chloride, sodium sulphate and ammonium sulphate, on cutinase partition was also studied. The results lead to the conclusion that aqueous two-phase systems composed of PEG and hydroxypropyl starch are not efficient in the purification of cutinase. In the majority of cases, the partition coefficients were very close to 1, with pH being the factor which affects most cutinase partition. Partition coefficients were significantly improved when salts were added to the systems. For PEG 4000–Reppal PES 100 [at pH 4.0; 0.5 M (NH₄)₂SO₄], the partition coefficient for cutinase was 3.7, while a value of 12 was obtained for PEG 4000–HPS (at pH 4.0; 1 M NaCl). An isoelectric point (pI) of 7.8 was confirmed for cutinase by constructing a cross partition graphic from the results obtained in the experiments with different salts.     

Factors affecting the growth form of Aspergillus terreus NRRL 1960 in relation to itaconic acid fermentation

The effect of medium composition on the growth form of Aspergillus terreus NRRL 1960 in relation to itaconic acid fermentation has been studied. Four types of mycelial pellets were obtained under the conditions used and may be classified as (a) frayed and loose with 0.1–0.5 mm diameter (b) compact with 0.1–0.5 mm diameter (c) loose with 0.5–2.0 mm diameter and (d) compact with 0.5–2.0 mm diameter. Their respective maximum specific rates of formation and yields of itaconic acid, based on 100 g sucrose supplied, were (a) 1.25 mol mg^–1h^–1 and 55–59 g, (b) 0.27–0.43 mol mg^–1 h^–1 and 26–38 g, (c) 0.75–0.90 mol mg^–1 h^–1 and 45–51 g and (d) 0.12 mol mg^–1 h^–1 and 10 g. The presence of Ca²⁺, Zn²⁺ and Fe²⁺ in the basal medium at concentrations of 23.3 mg/100 ml, 0.01 mg/100 ml and 0.006 mg/100 ml respectively were found to be adequate and crucial in obtaining the desired outgrowth for both high production rates and consistent yields of itaconic acid. The further addition of either commercial plaster of Paris or analytical-reagent-grade CaSO₄, especially when activated by heating to 530°C and present in excess of solubility, results in small and frayed pellets, which lead to itaconic acid yields of 55–59 g acid/100 g sugar supplied.     

Somatic embryogenesis of the banana hybrid cultivar FHIA-18 (AAAB) in liquid medium and scaled-up in a bioreactor

The development of somatic embryos in liquid culture medium has a number of advantages for large-scale propagation of plants. This paper describes an improved system for the mass propagation via somatic embryogenesis of the banana hybrid cultivar FHIA-18 (AAAB). Explants from immature male flowers were used to form high frequency embryogenic tissue, this tissue was then used to establish embryogenic cell suspensions in a basic MS medium plus 1.0 mg l^–1 biotin, 100 mg l^–1 glutamine, 100 mg l^–1 malt extract (Sigma), 1.0 mg l^–1 2,4-D and 45 g l^–1 sucrose. Secondary multiplication of somatic embryos was achieved in liquid media in rotary shaker and in bioreactors. The number of embryos per litre obtained with 80.0% DO₂ and effects of pH were also studied. A high regeneration percentage of plants were obtained (89.3%) in only 1 month of culture, somatic embryos were then placed to germinate in temporary immersion systems and field testing of somaclonal variation.     

The organic carbon budget of a shallow arctic tundra lake on the Tuktoyaktuk Peninsula,N.W.T., Canada

The organic carbon cycle of a shallow, tundra lake (mean depth 1.45 m) was followed for 5 weeks of the open water period by examining CO₂ fluxes through benthic respiration and anaerobic decomposition, photosynthesis of benthic and phytoplankton communities and gas exchange at the air-water interface. Total photosynthesis (as consumption of carbon dioxide) was 37.5 mmole C m^–2 d^–1, 83% of which was benthic and macrophytic. By direct measurement benthic respiration exceeded benthic photosynthesis by 6.6 mmole C m^–2 d^–1. The lake lost 1.4 × 10⁶ moles C in two weeks after ice melted by degassing C0₂, and 6.8 mmole C m^–2 d^–1 (1.5 × 10⁶ moles) during the remainder of the open water period; 2.2 mmole C m² d^–1 of this was release Of CO₂ stored in the sediments by cryoconcentration the previous winter. Anaerobic microbial decomposition was only 4% of the benthic aerobic respiration rate of 38 mmole C m^–2 d^–1. An annual budget estimate for the lake indicated that 50% of the carbon was produced by the benthic community, 20% by phytoplankton, and 30% was allochthonous material. The relative contribution of allochthonous input was in accordance with measurement of the ¹⁵N of sedimented organic matter.     

Synthesis,characterization and swelling behaviors of sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent

A novel sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent was prepared by graft copolymerization with sodium alginate, acrylic acid and sodium humate in aqueous solution, using N,N’-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The effects of crosslinker, sodium alginate and sodium humate content on water absorbency of the superabsorbent were studied. The swelling behavior in solutions of various pH and the swelling kinetics in saline solutions (5 mmol/L NaCl and CaCl₂) were also investigated. The results from IR analysis showed that both sodium alginate and sodium humate react with the acrylic acid monomer during the polymerization process. The introduction of sodium humate into the sodium alginate-g-poly(acrylic acid) system could enhance the water absorbency and the superabsorbent containing 10 wt% sodium humate acquired the highest water absorbency (1380 g/g in distilled water and 83 g/g in 0.9 wt% NaCl solution).     

Mixed inhibitions by methanol, furfural and acetic acid on xylitol production by Candida guilliermondii

Xylose production by Candida guilliermondii FTI 20037 was carried out in a synthetic medium in the presence of 0–100 g methanol l^–1, 0–0.7 g furfural l^–1 or 0–1.3 g acetic acid l^–1. Kinetic results show a mixed inhibition mechanism in all three cases. Maximum specific productivity and saturation constant for product formation were, in the absence of inhibition, 3.6 g_P g_X ^–1 h^–1 and 232 g_S l^–1, respectively, while the inhibition constants, K _i and K _i, were 17 and 50 g methanol l^–1, 0.62 and 7.0 g furfural l^–1, 0.69 and 3.5 g acetic acid l^–1, which suggests the following order of inhibition: furfural > acetic acid > methanol.     

Plant regeneration from thin cell layers in Spinacia oleracea

Caulogenesis and somatic embryogenesis were induced from transverse thin cell layers (tTCLs) of two European (Spinacia oleracea L.) spinach genotypes. Regeneration occurred mostly when tTCLs had been excised from seedlings grown on a preconditioning medium consisting of White's macroelements, Nitsch's microelements, Murashige and Skoog's (MS) vitamins, 6 g l^–1 agar and 20 g l^–1 glucose. The explants were cultured on MS medium supplemented with sucrose (10, 30, 50 or 80 g l^–1) or fructose (5, 10 or 30 g l^–1) and several combinations of indole-3-acetic acid (IAA), -naphtalene acetic acid (NAA), 6-benzylaminopurine (BAP) and gibberellic acid (GA₃). Most of the regeneration events were obtained from root explants of the cultivar Carpo. The best result was observed on MS medium supplemented with 50 g l^–1 sucrose, 100 M NAA, 1 M BAP and 10 M GA₃. After an 8-week culture, the calluses were transferred onto MS medium where shoots and somatic embryos appeared 1 week later. The best root development was obtained on MS medium supplemented with 4.9 M indole-3-butyric acid (IBA) and 8 g l^–1 Phytagel. The plantlets were, then, transferred to soil and developed into well-conformed, fertile plants.     

In vitro Growth and Shoot Multiplication of Achras zapota in a Controlled Carbon Dioxide Environment

The culture vessels with multiplying shoots of Achras zapota L. on Schenk and Hildebrandt (SH) medium containing 8.88 M 6-benzylaminopurine (BAP) with or without sucrose were kept under varied CO₂ concentrations ranging from 0.6 to 40.0 g m^–3 using different concentrations of sodium bicarbonate (NaHCO₃), sodium carbonate (Na₂CO₃), potassium bicarbonate (KHCO₃), and potassium carbonate (K₂CO₃) in small acrylic chambers. Complete absence of carbon source caused death of shoots within 20 d. Under elevated concentrations of CO₂ (10.0 and 40.0 g m^–3) the shoots grew photoautotrophically on sucrose-free medium. The growth of cultures was better at 40.0 g (CO₂) m^–3 than on 3.0 % sucrose under ambient air of growth room. However, the best response was obtained at 10.0 g (CO₂) m^–3 and 3.0 % sucrose where maximum number of shoots, shoot length, fresh and dry mass, total number of leaves and leaf area was observed.     

Synthesis and characterization of a novel super-absorbent based on chemically modified pulverized wheat straw and acrylic acid

In order to develop an eco-friendly polymer, the material was prepared from pulverized wheat straw by chemical methods. And a super-absorbent hydrogel has been synthesized with chemically modified pulverized wheat straw (CMPWS) and acrylic acid (AA) in aqueous solution. Factors, such as weight ratio of AA to CMPWS, the amount of initiator and cross-linker, temperature and neutralization degree of AA that influence absorbencies of super-absorbent were investigated. Moreover, the super-absorbent had been proved with expectant polymerization structure and good thermo-stability via IR spectrum and TGA analysis. The morphological features were evidenced by SEM images. The excellent product was obtained with the absorbencies of 417 g/g in distilled water and 45 g/g in 0.9 wt% NaCl solution.