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Greene AF, Abbel R, Vaidya AA, Tanjay Q, Chen Y, Risani R, Saggese T, Barbier M, Petcu M, West M, Theobald B, Gaugler E, Parker K. Environmentally Benign Fast-Degrading Conductive Composites. Biomacromolecules 2024; 25:455-465. [PMID: 38147683 DOI: 10.1021/acs.biomac.3c01077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
An environmentally benign conductive composite that rapidly degrades in the presence of warm water via enzyme-mediated hydrolysis is described. This represents the first time that hydrolytic enzymes have been immobilized onto eco-friendly conductive carbon sources with the express purpose of degrading the encapsulating biodegradable plastic. Amano Lipase (AL)-functionalized carbon nanofibers (CNF) were compounded with polycaprolactone (PCL) to produce the composite film CNFAL-PCL (thickness ∼ 600 μm; CNFAL = 20.0 wt %). To serve as controls, films of the same thickness were also produced, including CNF-AL5-PCL (CNF mixed with AL and PCL; CNF = 19.2 wt % and AL = 5.00 wt %), CNF-PCL (CNF = 19.2 wt %), ALx-PCL (AL = x = 1.00 or 5.00 wt %), and PCL. The electrical performance of the CNF-containing composites was measured, and conductivities of 14.0 ± 2, 22.0 ± 5, and 31.0 ± 6 S/m were observed for CNFAL-PCL, CNF-AL5-PCL, and CNF-PCL, respectively. CNFAL-PCL and control films were degraded in phosphate buffer (2.00 mg/mL film/buffer) at 50 °C, and their average percent weight loss (Wtavg%) was recorded over time. After 3 h CNFAL-PCL degraded to a Wtavg% of 90.0% and had completely degraded after 8 h. This was considerably faster than CNF-AL5-PCL, which achieved a total Wtavg% of 34.0% after 16 days, and CNF-PCL, which was with a Wtavg% of 7.00% after 16 days. Scanning electron microscopy experiments (SEM) found that CNFAL-PCL has more open pores on its surface and that it fractures faster during degradation experiments which exposes the interior enzyme to water. An electrode made from CNFAL-PCL was fabricated and attached to an AL5-PCL support to form a fast-degrading thermal sensor. The resistance was measured over five cycles where the temperature was varied between 15.0-50.0 °C. The sensor was then degraded fully in buffer at 50 °C over a 48 h period.
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Affiliation(s)
- Angelique F Greene
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Robert Abbel
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Alankar A Vaidya
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Queenie Tanjay
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Yi Chen
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Regis Risani
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Taryn Saggese
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Maxime Barbier
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Miruna Petcu
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Mark West
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Beatrix Theobald
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Eva Gaugler
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
| | - Kate Parker
- Te Papa Tipu Innovation Park, Ti̅tokorangi Drive, Rotorua, New Zealand 3010
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Wijeyekoon SLJ, Vaidya AA. Woody biomass as a potential feedstock for fermentative gaseous biofuel production. World J Microbiol Biotechnol 2021; 37:134. [PMID: 34258684 DOI: 10.1007/s11274-021-03102-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/01/2021] [Indexed: 01/22/2023]
Abstract
Biogas and biohydrogen are compatible gaseous biofuels that can be blended with natural gas for reticulated fuel supply to reduce greenhouse gas emissions. Sustainably grown woody biomass is emerging as a potential feedstock in the production of biofuels. Woody biomass is widely available, uses non-arable land for plantation, does not require synthetic fertilisers to grow and acts as a carbon sink. The cellulose and hemicellulose fractions of wood are renewable sources of sugars that can be used for fermentative production of gaseous biofuels. However, widespread use of wood as a gaseous biofuel feedstock is constrained due to the recalcitrant nature of wood to enzymatic hydrolysis. Pretreatment makes cellulose and hemicellulose accessible to microbial enzymes to produce fermentable sugars. Here we review wood composition, its structure and different pretreatment techniques in the context of their effects on deconstruction of wood to improve hydrolysis and fermentative gaseous fuel production. The anaerobic digestion of pretreated wood for biogas and dark fermentation for biohydrogen production are discussed with reference to gas yields. Key advancements in lab-scale research are described for pretreatments and for pure, co- and mixed culture fermentations. Limitations to yield improvements are identified and future perspectives and prospects of gaseous biofuel production from woody biomass are discussed, with reference to new developments in engineered biocatalysts and process integration.
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Affiliation(s)
| | - Alankar A Vaidya
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua, 3046, New Zealand.
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Vaidya AA, Hussain I, Gaugler M, Smith DA. Synthesis of graft copolymers of chitosan-poly(caprolactone) by lipase catalysed reactive extrusion. Carbohydr Polym 2019; 217:98-109. [DOI: 10.1016/j.carbpol.2019.03.081] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 03/24/2019] [Accepted: 03/25/2019] [Indexed: 11/29/2022]
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Fahmy M, Sohel MI, Vaidya AA, Jack MW, Suckling ID. Does sugar yield drive lignocellulosic sugar cost? Case study for enzymatic hydrolysis of softwood with added polyethylene glycol. Process Biochem 2019. [DOI: 10.1016/j.procbio.2019.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Suckling ID, Jack MW, Lloyd JA, Murton KD, Newman RH, Stuthridge TR, Torr KM, Vaidya AA. A mild thermomechanical process for the enzymatic conversion of radiata pine into fermentable sugars and lignin. Biotechnol Biofuels 2017; 10:61. [PMID: 28293291 PMCID: PMC5345204 DOI: 10.1186/s13068-017-0748-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 03/01/2017] [Indexed: 05/13/2023]
Abstract
BACKGROUND Conversion of softwoods into sustainable fuels and chemicals is important for parts of the world where softwoods are the dominant forest species. While they have high theoretical sugar yields, softwoods are amongst the most recalcitrant feedstocks for enzymatic processes, typically requiring both more severe pretreatment conditions and higher enzyme doses than needed for other lignocellulosic feedstocks. Although a number of processes have been proposed for converting softwoods into sugars suitable for fuel and chemical production, there is still a need for a high-yielding, industrially scalable and cost-effective conversion route. RESULTS We summarise work leading to the development of an efficient process for the enzymatic conversion of radiata pine (Pinus radiata) into wood sugars. The process involves initial pressurised steaming of wood chips under relatively mild conditions (173 °C for 3-72 min) without added acid catalyst. The steamed chips then pass through a compression screw to squeeze out a pressate rich in solubilised hemicelluloses. The pressed chips are disc-refined and wet ball-milled to produce a substrate which is rapidly saccharified using commercially available enzyme cocktails. Adding 0.1% polyethylene glycol during saccharification was found to be particularly effective with these substrates, reducing enzyme usage to acceptable levels, e.g. 5 FPU/g OD substrate. The pressate is separately hydrolysed using acid, providing additional hemicellulose-derived sugars, for an overall sugar yield of 535 kg/ODT chips (76% of theoretical). The total pretreatment energy input is comparable to other processes, with the additional energy for attrition being balanced by a lower thermal energy requirement. This pretreatment strategy produces substrates with low levels of fermentation inhibitors, so the glucose-rich mainline and pressate syrups can be fermented to ethanol without detoxification. The lignin from the process remains comparatively unmodified, as evident from the level of retained β-ether interunit linkages, providing an opportunity for conversion into saleable co-products. CONCLUSIONS This process is an efficient route for the enzymatic conversion of radiata pine, and potentially other softwoods, into a sugar syrup suitable for conversion into fuels and chemicals. Furthermore, the process uses standard equipment that is largely proven at commercial scale, de-risking process scale-up.
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Affiliation(s)
| | - Michael W. Jack
- Scion, 49 Sala St, Rotorua, 3046 New Zealand
- Department of Physics, University of Otago, PO Box 56, Dunedin, 9054 New Zealand
| | | | | | | | - Trevor R. Stuthridge
- Scion, 49 Sala St, Rotorua, 3046 New Zealand
- FP Innovations, 2665 East Mall, Vancouver, BC V6T 1Z4 Canada
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Vaidya AA, Donaldson LA, Newman RH, Suckling ID, Campion SH, Lloyd JA, Murton KD. Micromorphological changes and mechanism associated with wet ball milling of Pinus radiata substrate and consequences for saccharification at low enzyme loading. Bioresour Technol 2016; 214:132-137. [PMID: 27131293 DOI: 10.1016/j.biortech.2016.04.084] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 04/15/2016] [Accepted: 04/16/2016] [Indexed: 05/26/2023]
Abstract
In this work, substrates prepared from thermo-mechanical treatment of Pinus radiata chips were vibratory ball milled for different times. In subsequent enzymatic hydrolysis, percent glucan conversion passed through a maximum value at a milling time of around 120min and then declined. Scanning electron microscopy revealed breakage of fibers to porous fragments in which lamellae and fibrils were exposed during ball milling. Over-milling caused compression of the porous fragments to compact globular particles with a granular texture, decreasing accessibility to enzymes. Carbon-13 NMR spectroscopy showed partial loss of interior cellulose in crystallites, leveling off once fiber breakage was complete. A mathematical model based on observed micromorphological changes supports ball milling mechanism. At a low enzyme loading of 2FPU/g of substrate and milling time of 120min gave a total monomeric sugar yield of 306g/kg of pulp which is higher than conventional pretreatment method such as steam exploded wood.
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Affiliation(s)
- Alankar A Vaidya
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand.
| | - Lloyd A Donaldson
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - Roger H Newman
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - Ian D Suckling
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - Sylke H Campion
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - John A Lloyd
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - Karl D Murton
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
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Vaidya AA, Gaugler M, Smith DA. Green route to modification of wood waste, cellulose and hemicellulose using reactive extrusion. Carbohydr Polym 2015; 136:1238-50. [PMID: 26572467 DOI: 10.1016/j.carbpol.2015.10.033] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 09/21/2015] [Accepted: 10/11/2015] [Indexed: 11/19/2022]
Abstract
A large volume of wood waste is produced in timber processing industry which traditionally used in low value applications. Here, value addition to the wood waste (Sander dust) and cellulose, hemicellulose isolated thereof by functionalisation using cyclic anhydrides in a solvent-free and green reactive extrusion process is reported. The effect of extrusion temperature, catalyst and different weight ratios of Sander dust (SD):succinic anhydride (SA) on the esterification reaction is evaluated. The esterified products were characterised by the acid value, degree of substitution (DS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), solid state (13)C NMR and thermo-gravimetric analysis (TGA). Under optimum extrusion conditions, mixed esters are formed, with highest acid value obtained for succinylation of cellulose (0.122 g/g at DS of 0.350) which is two times higher compared to succinylated SD (0.059 g/g at a weight gain of 0.452) and hemicellulose (0.043 g/g at DS of 0.290). The reactivity trend for individual anhydride was: (1) SA-Cellulose>SD>hemicellulose; (2) maleic anhydride (MA)-SD>hemicellulose>cellulose and (3) dodecenyl succinic anhydride (DDSA)-SD ≈ cellulose ≫ hemicellulose. The pendant free carboxyl groups generated through functionalisation of wood waste, cellulose and hemicellulose without the presence of polymeric carriers will allow more tailored or targeted modification of wood-plastic composites.
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Affiliation(s)
- Alankar A Vaidya
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand.
| | - Marc Gaugler
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
| | - Dawn A Smith
- Scion, Te Papa Tipu Innovation Park, 49 Sala Street, Rotorua 3046, New Zealand
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Cameron H, Campion SH, Singh T, Vaidya AA. Improved saccharification of steam-exploded Pinus radiata on supplementing crude extract of Penicillium sp. 3 Biotech 2015; 5:221-225. [PMID: 28324577 PMCID: PMC4362734 DOI: 10.1007/s13205-014-0212-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 03/21/2014] [Indexed: 11/24/2022] Open
Abstract
Commercially available enzymes do not contain all the necessary softwood-specific accessory enzymes to obtain high saccharification efficiency. In this work, six saprophytic fungi obtained from Pinus radiata plantation site were screened for the putative softwood-specific accessory enzyme, β-mannanase. A Penicillium sp. was found to produce β-mannanase in both solid (31.6 units/g of dry biomass) and liquid (117 units/g of dry biomass) cultures using locust bean gum as an inducer after 2 weeks of incubation. The saccharification of steam-exploded Pinus radiata was 7.8 % w/w improved when the crude extract of Penicillium sp. was added to a mixture of commercial enzymes.
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Affiliation(s)
- Hamish Cameron
- Faculty of Science and Engineering, University of Waikato, Private Bag 3105, Hamilton, New Zealand
| | - Sylke H Campion
- Scion, Te Papa Tipu Innovation Park, Private Bag 3020, Rotorua, 3046, New Zealand
| | - Tripti Singh
- Scion, Te Papa Tipu Innovation Park, Private Bag 3020, Rotorua, 3046, New Zealand
| | - Alankar A Vaidya
- Scion, Te Papa Tipu Innovation Park, Private Bag 3020, Rotorua, 3046, New Zealand.
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Newman RH, Vaidya AA, Sohel MI, Jack MW. Optimizing the enzyme loading and incubation time in enzymatic hydrolysis of lignocellulosic substrates. Bioresour Technol 2013; 129:33-8. [PMID: 23232221 DOI: 10.1016/j.biortech.2012.11.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 11/05/2012] [Accepted: 11/05/2012] [Indexed: 05/14/2023]
Abstract
A mathematical model for costing enzymatic hydrolysis of lignocellulosics is presented. This model is based on three variable parameters describing substrate characteristics and three unit costs for substrate, enzymes and incubation. The model is used to minimize the cost of fermentable sugars, as intermediate products on the route to ethanol or other biorefinery products, by calculating optimized values of enzyme loading and incubation time. This approach allows comparisons between substrates, with processing conditions optimized independently for each substrate. Steam-exploded pine wood was hydrolyzed in order to test the theoretical relationship between sugar yield and processing conditions.
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Affiliation(s)
- Roger H Newman
- Scion, Private Bag 3020, Rotorua Mail Centre, Rotorua 3046, New Zealand.
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Newman RH, Vaidya AA, Campion SH. A mathematical model for the inhibitory effects of lignin in enzymatic hydrolysis of lignocellulosics. Bioresour Technol 2013; 130:757-762. [PMID: 23340076 DOI: 10.1016/j.biortech.2012.12.122] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 11/09/2012] [Accepted: 12/16/2012] [Indexed: 06/01/2023]
Abstract
A new model for enzymatic hydrolysis of lignocellulosic biomass distinguishes causal influences from enzyme deactivation and restrictions on the accessibility of cellulose. It focuses on calculating the amount of unreacted cellulose at cessation of enzyme activity, unlike existing models that were constructed for calculating the time dependence of conversion. There are three adjustable parameters: (1) 'occluded cellulose' is defined as cellulose that cannot be hydrolysed regardless of enzyme loading or incubation time, (2) a 'characteristic enzyme loading' is sufficient to hydrolyse half of the non-occluded cellulose, (3) a 'mechanism index' measures deviations from first-order kinetics. This model was used to predict that the optimal incubation temperature is lower for lignocellulosics than for pure cellulose. For steam-exploded pine wood after 96h incubation, occluded cellulose was 24% and 26% at 30°C and 50°C, and the characteristic enzyme loadings were 10 and 18FPU/g substrate, respectively.
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Affiliation(s)
- Roger H Newman
- Scion, Private Bag 3020, Rotorua Mail Centre, Rotorua 3046, New Zealand.
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Kale VP, Vaidya AA. Molecular Mechanisms Behind the Dose-Dependent Differential Activation of MAPK Pathways Induced by Transforming Growth Factor-β1 in Hematopoietic Cells. Stem Cells Dev 2004; 13:536-47. [PMID: 15588511 DOI: 10.1089/scd.2004.13.536] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Transforming growth factor-beta (TGF-beta) controls a wide range of cellular responses, including cell proliferation, lineage determination, differentiation, and apoptosis, and figures prominently in animal development. It is considered as a pleiotropic factor because it can exert a positive or negative effect on various cellular processes depending on developmental stage of the target cell, its microenvironment, and also its biochemical make up. It has been shown to have a strong inhibitory effect on hematopoietic stem cell proliferation and differentiation. We have earlier shown that TGF-beta1 exerts a bidirectional effect on hematopoietic cell proliferation as a function of its concentration. Although it acted as an inhibitor at high concentrations, at low concentrations it stimulated the stem/progenitor cells. We also provided evidence that the differential activation of mitogen-activated protein kinase pathways was responsible for the observed bidirectional effect. In the present study, we examined the molecular mechanism behind this phenomenon. We observed that the high inhibitory concentrations of TGF-beta1 induced a strong phosphorylation of SMAD 3 and also activated stress kinase-related transcription factors, namely c-Jun and ATF-2. On the other hand, low stimulatory concentrations acted in a SMAD 3-independent pathway and activated STAT proteins. Our results clearly show that differential activation of signal transduction pathways by TGF-beta1 as a function of its concentration underlies its bidirectional effect on hematopoietic cells.
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Affiliation(s)
- V P Kale
- National Center for Cell Science, Ganeshkhind, Pune 411 007, India
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Vaidya AA, Lele BS, Kulkarni MG, Mashelkar RA. Thermoprecipitation of lysozyme from egg white using copolymers of N-isopropylacrylamide and acidic monomers. J Biotechnol 2001; 87:95-107. [PMID: 11278034 DOI: 10.1016/s0168-1656(00)00382-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Thermoprecipitation of lysozyme from egg white was demonstrated using copolymers of N-isopropylacrylamide with acrylic acid, methacrylic acid, 2-acryloylamido-2-methylpropane-sulfonic acid and itaconic acid, respectively. Polymers synthesized using molar feed ratio of N-isopropylacrylamide:acidic monomers of 98:2 exhibited lower critical solution temperatures in the range of 33--35 degrees C. These polymers exhibited electrostatic interactions with lysozyme and inhibited its bacteriolytic activity. The concentration of acidic groups required to attain 50% relative inhibition of lysozyme by the polymers, was 10(4)--10(5) times lower than that required for the corresponding monomers. This was attributed to the multimeric nature of polymer-lysozyme binding. More than 90% lysozyme activity was recovered from egg white. Polymers exhibited reusability up to at least 16 cycles with retention of >85% recovery of specific activity from aqueous solution. In contrast, copolymer comprising natural inhibitor of lysozyme i.e. poly (N-isopropylacrylamide-co-O-acryloyl N-acetylglucosamine) lost 50% recovery of specific activity. Thermoprecipitation using these copolymers, which enables very high recovery of lysozyme from egg white, would be advantageous over pH sensitive polymers, which generally exhibit lower recovery.
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Affiliation(s)
- A A Vaidya
- Chemical Engineering Division, National Chemical Laboratory, Polymer Science and Engineering Group, Pune 411 008, India
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Abstract
Copolymers of N-isopropylacrylamide and N-acryloyl amino acid spacers of varying chain length were synthesized. p-Aminobenzamidine (PABA) was chemically linked to the pendant carboxyl groups of these polymers to obtain thermoprecipitating affinity polymers. The inhibition constant (Ki) of these polymers for trypsin decreased, i. e., the efficiency of PABA-trypsin binding increased with increase in the spacer chain length. The polymer to which PABA was linked through a spacer of five methylene groups exhibited eleven times lower Ki than that of the polymer containing PABA without a spacer. Investigations on model inhibitors N-acyl-p-aminobenzamidines showed that this enhancement in trypsin binding by the polymers was due to the spacer as well as to microenvironmental effects. Recovery and specific activity of the trypsin recovered increased with the spacer chain length. Separation of trypsin from a mixture of trypsin and chymotrypsin was also enhanced with the spacer chain length. The inhibition constants of these affinity polymers were not adversely affected by the crowding effect. Copyright 1999 John Wiley & Sons, Inc.
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Affiliation(s)
- AA Vaidya
- Polymer Science & Engineering Group, Chemical Engineering Division, National Chemical Laboratory, Pune 411 008, India
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