19 research outputs found

    Microwave-assisted synthesis of levulinic acid from low-cost, sustainable feedstocks using organic acids as green catalysts

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    BACKGROUND: Modern day scientific endeavour strives towards global sustainability through the smart utilisation of renewable resources as base materials for chemicals. Until now, the most common commercial process to produce levulinic acid (a mass-produced platform chemical) depends on a two-stage mineral acid-catalysed reaction, which generates harmful environmental waste. In this work, an environmentally friendly levulinic acid production route using less harmful organic acids assisted by microwave heating from biomass feedstocks is reported for the first time. RESULTS: Using aluminum sulfate as a green Lewis acid catalyst and seven organic acids, levulinic acid was successfully produced from barley straw under microwave heating, with maleic acid giving the highest catalytic conversion. A Response Surface Methodology (RSM) approach was used to rapidly and effectively examine the effect of five reaction variables on the productivity of the levulinic acid. A wide range of different biomass wastes (barley straw, brewery waste, olive cake, spent tea leaves and potato, tomato, and mandarin peels) were subsequently screened to produce the levulinic acid. The highest yield of 86 wt% based on cellulose content from mandarin peel (a value comparable to a lengthier ‘non-green’ route) was achieved under the following optimized reaction conditions: 180 °C, 38 min, 2 M maleic acid concentration, 0.1 g Al 2(SO 4) 3 and 1:22 biomass: maleic acid ratio (g mL −1). CONCLUSIONS: The proposed method is a promising new route towards the green, high yield production of levulinic acid from a variety of agricultural and household lignocellulosic biomass wastes, without the need for pre-treatment

    Multi-cycle recovery of lactoferrin and lactoperoxidase from crude whey using fimbriated high-capacity magnetic cation exchangers and a novel "rotor-stator" high-gradient magnetic separator

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    Cerium (IV) initiated "graft-from" polymerization reactions were employed to convert M-PVA magnetic particles into polyacrylic acid-fimbriated magnetic cation exchange supports displaying ultra-high binding capacity for basic target proteins. The modifications, which were performed at 25mg and 2.5g scales, delivered maximum binding capacities (Q) for hen egg white lysozyme in excess of 320mgg, combined with sub-micromolar dissociation constants (0.45-0.69μm) and "tightness of binding" values greater than 49Lg. Two batches of polyacrylic acid-fimbriated magnetic cation exchangers were combined to form a 5g pooled batch exhibiting Q values for lysozyme, lactoferrin, and lactoperoxidase of 404, 585, and 685mgg, respectively. These magnetic cation exchangers were subsequently employed together with a newly designed "rotor-stator" type HGMF rig, in five sequential cycles of recovery of lactoferrin and lactoperoxidase from 2L batches of a crude sweet bovine whey feedstock. Lactoferrin purification performance was observed to remain relatively constant from one HGMF cycle to the next over the five operating cycles, with yields between 40% and 49% combined with purification and concentration factors of 37- to 46-fold and 1.3- to 1.6-fold, respectively. The far superior multi-cycle HGMF performance seen here compared to that observed in our earlier studies can be directly attributed to the combined use of improved high capacity adsorbents and superior particle resuspension afforded by the new "rotor-stator" HGMS design. © 2013 Wiley Periodicals, Inc

    Integrated system for temperature-controlled fast protein liquid chromatography. II. Optimized adsorbents and ‘single column continuous operation’

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    Continued advance of a new temperature-controlled chromatography system, comprising a column filled with thermoresponsive stationary phase and a travelling cooling zone reactor (TCZR), is described. Nine copolymer grafted thermoresponsive cation exchangers (thermoCEX) with different balances of thermoresponsive (N-isopropylacrylamide), hydrophobic (N-tert-butylacrylamide) and negatively charged (acrylic acid) units were fashioned from three cross-linked agarose media differing in particle size and pore dimensions. Marked differences in grafted copolymer composition on finished supports were sourced to base matrix hydrophobicity. In batch binding tests with lactoferrin, maximum binding capacity (q max) increased strongly as a function of charge introduced, but became increasingly independent of temperature, as the ability of the tethered copolymer networks to switch between extended and collapsed states was lost. ThermoCEX formed from Sepharose CL-6B (A2), Superose 6 Prep Grade (B2) and Superose 12 Prep Grade (C1) under identical conditions displayed the best combination of thermoresponsiveness (q max,50°C/q max,10°C ratios of 3.3, 2.2 and 2.8 for supports 'A2', 'B2' and 'C1' respectively) and lactoferrin binding capacity (q max,50°C ~56, 29 and 45mg/g for supports 'A2', 'B2' and 'C1' respectively), and were selected for TCZR chromatography. With the cooling zone in its parked position, thermoCEX filled columns were saturated with lactoferrin at a binding temperature of 35°C, washed with equilibration buffer, before initiating the first of 8 or 12 consecutive movements of the cooling zone along the column at 0.1mm/s. A reduction in particle diameter (A2→B2) enhanced lactoferrin desorption, while one in pore diameter (B2→C1) had the opposite effect. In subsequent TCZR experiments conducted with thermoCEX 'B2' columns continuously fed with lactoferrin or 'lactoferrin+bovine serum albumin' whilst simultaneously moving the cooling zone, lactoferrin was intermittently concentrated at regular intervals within the exiting flow as sharp uniformly sized peaks. Halving the lactoferrin feed concentration to 0.5mg/mL, slowed acquisition of steady state, but increased the average peak concentration factor from 7.9 to 9.2. Finally, continuous TCZR mediated separation of lactoferrin from bovine serum albumin was successfully demonstrated. While the latter's presence did not affect the time to reach steady state, the average lactoferrin mass per peak and concentration factor both fell (respectively from 30.7 to 21.4mg and 7.9 to 6.3), and lactoferrin loss in the flowthrough between elution peaks increased (from 2.6 to 12.2mg). Fouling of the thermoCEX matrix by lipids conveyed into the feed by serum albumin is tentatively proposed as responsible for the observed drops in lactoferrin binding and recovery

    Integrated system for temperature-controlled fast protein liquid chromatography comprising improved copolymer modified beaded agarose adsorbents and a travelling cooling zone reactor arrangement

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    An integrated approach to temperature-controlled chromatography, involving copolymer modified agarose adsorbents and a novel travelling cooling zone reactor (TCZR) arrangement, is described. Sepharose CL6B was transformed into a thermoresponsive cation exchange adsorbent (thermoCEX) in four synthetic steps: (i) epichlorohydrin activation; (ii) amine capping; (iii) 4,4′-azobis(4-cyanovaleric acid) immobilization; and ‘graft from’ polymerization of poly(N-isopropylacrylamide-co-N-tert-butylacrylamide-co-acrylic acid-co- N,N′-methylenebisacrylamide). FT-IR, 1H NMR, gravimetry and chemical assays allowed precise determination of the adsorbent’s copolymer composition and loading, and identified the initial epoxy activation step as a critical determinant of ‘on-support’ copolymer loading, and in turn, protein binding performance. In batch binding studies with lactoferrin, thermoCEX’s binding affinity and maximum adsorption capacity rose smoothly with temperature increase from 20 to 50 ºC. In temperature shifting chromatography experiments employing thermoCEX in thermally-jacketed columns, 44 – 51% of the lactoferrin adsorbed at 42 ºC could be desorbed under binding conditions by cooling the column to 22 ºC, but the elution peaks exhibited strong tailing. To more fully exploit the potential of thermoresponsive chromatography adsorbents, a new column arrangement, the TCZR, was developed. In TCZR chromatography, a narrow discrete cooling zone (special assembly of copper blocks and Peltier elements) is moved along a bespoke fixed-bed separation columnfilled with stationary phase. In tests with thermoCEX, it was possible to recover 65% of the lactoferrin bound at 35 ºC using 8 successive movements of the cooling zone at a velocity of 0.1 mm/s; over half of the recovered protein was eluted in the first peak in more concentrated form than in the feed. Intra-particle diffusion of desorbed protein out of the support pores, and the ratio between the velocities of the cooling zone and mobile phase were identified as the main parameters affecting TCZR performance. In contrast to conventional systems, which rely on cooling the 3 whole column to effect elution and permit only batch-wise operation, TCZR chromatography generates sharp concentrated elution peaks without tailing effects and appears ideally suited for continuous operation