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1. The dynamics of sediment-associated contaminants over a transition from drought to multiple flood events in a lowland UK catchment

Author

Pulley, Simon, Foster, Ian D L, and Antunes, A Paula M

Abstract

Fine sediment in suspended form, recently deposited overbank and in temporary storage on or in channel beds, was collected in the Nene basin during a period of drought through to a period of four high flows. The sediment was analysed for arsenic, copper, lead, phosphorus and zinc concentrations with the aim of investigating their sources, movement, temporary storage and potential for environmental harm. Copper, lead and zinc probably originated from urban street dusts, phosphorus (originally in dissolved form) from sewage effluent and arsenic from natural soils developed over ironstone. There was little difference in the metal or arsenic concentrations in the sediment under different flow conditions; instead, proximity to pollutant sources appeared to control their concentrations. Phosphorus in tributary sub-catchments probably adsorbed to sediment during periods of low flow but these sediments were flushed away during high flows and replaced by sediment with lower concentrations. However, concentrations of all pollutants in overbank sediments along the Nene's main channel were not reduced in successive flood events, suggesting no first flush effect. Only phosphorus accumulated on sediment at concentrations exceeding those of its catchment-based sources (e.g. street dusts, channel banks and catchment soils). This scavenging of aqueous phosphate by sediment explained the difference in behaviour between phosphorus, arsenic and heavy metals. The surface area and organic matter content were shown to have a small effect on contaminant concentrations. Street dust contaminants only exceeded predicted effect levels in close proximity to urban areas, suggesting a small potential for harm to the aquatic environment. Arsenic concentrations exceeded predicted effect levels in most sediment samples. However, it has been shown to be largely non-bioavailable in previously published research on the Nene, limiting its potential for significant environmental harm. Phosphorus concentrations in river sediments are high in comparison to the soils in the catchment and in comparison with sediment–P concentrations in other published lowland catchment studies, indicating a large potential for eutrophication should the Phosphorus be, or become, bioavailable.

Published
2016

3. A new formulation for the treatment of acid-deterioration (Red Rot) in historic leathers

Author

Lama, Anne, Fletcher, Yvette, Guthrie-Strachan, Jeffry, Covington, Anthony D, Antunes, A Paula M, Lama, Anne, Fletcher, Yvette, Guthrie-Strachan, Jeffry, Covington, Anthony D, and Antunes, A Paula M

Abstract

Conservation of acid-deteriorated historic leather (also commonly known as red rot) is an on-going concern as current treatment options are limited. Various products such as aqueous-based buffer salts, imidazole, ammonia vapour and aluminium di(isopropoxide) acetoacetate ester chelate (referred to as aluminium alkoxide in this study) have been used to treat acid-deterioration in historic leathers. Among the various products studied, aluminium alkoxide was found to be the most effective. However the effect of aluminium alkoxide when applied on its own may be limited due to its short-term stabilisation effect. A new formulation consisting of aluminium alkoxide and 5-ethyl-1-aza-3, 7-dioxabicyclo [3.3.0] octane (oxazolidine II) was used to treat acid-deterioration in historic leather. Acid-deteriorated leathers were treated with the new formulation and aged further by exposure to an acidic environment at 40°C and 30% relative humidity for up to 12 weeks. The acidic environment was created using sulfur dioxide and nitrogen dioxide. Corresponding untreated acid-deteriorated historic leathers were used as a negative control. The impact of the treatments and artificial ageing was determined by measuring the hydrothermal stability of the leather samples using differential scanning calorimetry (DSC) and pH of the aqueous extract. The results obtained showed that the formulation has collagen-stabilising properties, acid-buffering capacity as well as the capability to provide long-term protection against an artificially-created acidic environment.

Published
2015

4. Three-dimensional visualization of dermal skin structure using confocal laser scanning microscopy

Author

Antunes, A Paula M, Covington, Anthony D, Petford, Nick, Murray, T, and Wertheim, D

Subjects
QH201, QD415
Abstract

The properties and performance of collagen-based materials may be affected by the collagen fibre bundle pattern, orientation and weave. The aim of this study was to develop and apply methods to visualize the dermis using confocal laser scanning microscopy from thin tissue sections stained with haematoxylin and eosin. The data was processed to allow three-dimensional (3-D) visualization on a PC and using a 3-D immersive technology system. The 3-D visualization of the confocal microscope image stacks allowed the evaluation of the collagen macromolecular structure including the collagen fibre bundles. The methods developed provide a novel way of viewing complex organic structures with further potential applications in the medical field.

Published
2013

5. Towards zero solid waste: utilising tannery waste as a protein source for poultry feed

Author

Paul, Hiralal, Antunes, A Paula M, Covington, Anthony D, Evans, Paul, and Phillips, Paul S

Abstract

Zero waste is now a strongly emerging issue for sustainable industrial development where minimisation and utilisation of waste are a priority in the leather industry. In a tannery hides and skins converted in to leather through various processes. Approximately 20% (w/w) of the chrome containing tannery solid waste (TSW) is generated from one tonne of raw hides and skins. However, tannery solid waste may also be a resource if it is managed expertly as we move towards zero waste. This research illustrates the potential of tannery solid waste as a poultry feed additive. An oxidation method was used to achieve 95% of dechroming rate of chrome tanned waste followed with thermal and enzymatic treatment to produce gelatin solution and collagen concentrates. The thermal stability and fibre structure of samples were analysed by Differential Scanning Calorimeter (DSC) and Scanning Electron Microscope (SEM). Protein content and fourteen amino acid concentrations were determined using amino acid analysis. High Performance Liquid Chromatography (HPLC) was used to compare the amino acid composition with wheat and soya bean meal that is conventionally used in poultry feed. The nutrient requirements for poultry feed vary according to the purpose for which they have been developed. The high content of arginine, leucine, threonine, serine and methionine in the extract were of a sufficient level for poultry feed. Hexavalent chromium test was performed and showed that levels of the metal were low enough to be used in feed additives. In addition, the extracted product showed 75% digestibility (in vitro) and appears that treated TSW may be utilised in poultry feed, this demonstrates a clear example of waste utilisation. In Bangladesh plans are being formed to use the extract in poultry feed production.

Published
2013

6. Methods of isolation and identification of pathogenic and potential pathogenic bacteria from skins and tannery effluents

Author

Anne Lama, Margaret Bates, Covington, Anthony D., Allen, Stuart C. H., and Antunes, A. Paula M.

Subjects
QR75, TD896, TS967, TS965.5
Abstract

Currently there is no standard protocol available within the leather industry to isolate and identify pathogenic bacteria from hides, skins or tannery effluent. This study was therefore carried out to identify simple but effective methods for isolation and identification of bacterial pathogens from the effluent and skins during leather processing. Identification methods based on both phenotypic and genotypic characteristics were investigated. Bacillus cereus and Pseudomonas aeruginosa were used as indicator bacteria to evaluate the isolation and identification methods. Decontaminated calfskins were inoculated with a pure culture of the above mentioned bacterial species followed by a pre-tanning and chromium tanning processes. Effluent samples were collected and skins were swabbed at the end of each processing stage. Bacterial identification was carried out based on the phenotypic characteristics; such as colony appearance on selective solid media, cell morphology following a standard Gram-staining and spore staining techniques, and biochemical reactions, e.g., the ability of a bacterial species to ferment particular sugars and ability to produce certain enzymes. Additionally, an identification system based on bacterial phenotypic characteristics, known as Biolog® system was applied. A pulsed-filed gel electrophoresis (PFGE) method for bacterial DNA fingerprinting was also evaluated and used for the identification of the inoculated bacteria. The methods described in the study were found to be effective for the identification of pathogenic bacteria from skins and effluent.

Published
2013

11. The impacts of tracer selection and corrections for organic matter and particle size on the results of quantitative sediment fingerprinting. A case study from the Nene basin, UK

Author

Pulley, Simon, Foster, Ian D L, Antunes, A Paula M, Pulley, Simon, Foster, Ian D L, and Antunes, A Paula M

Abstract

In recent years, sediment fingerprinting methodologies have gained widespread adoption when tracing sediment provenance in geomorphological research. A wide variety of tracers have been employed in the published literature, with corrections for particle size and organic matter applied when the researcher judged them necessary. This paper aims to explore the errors associated with tracer use by a comparison of fingerprinting results obtained using fallout and lithogenic radionuclides, geochemical, and mineral magnetic tracers in a range of environments located in the Nene basin, UK. Specifically, fingerprinting was undertaken on lake, reservoir and floodplain sediment cores, on actively transported suspended sediment and on overbank and channel bed sediment deposits. Tracer groups were investigated both alone and in combination to determine the differences between their sediment provenance predictions and potential causes of these differences. Additionally, simple organic and particle size corrections were applied to determine if they improve the agreement between the tracer group predictions. Key results showed that when fingerprinting contributions from channel banks to actively transported or recently deposited sediments the tracer group predictions varied by 24% on average. These differences could not be clearly attributed to changes in the sediment during erosion or transport. Instead, the most likely cause of differences was the pre-existing spatial variability in tracer concentrations within sediment sources, combined with highly localised erosion. This resulted in the collected sediment source samples not being representative of the actual sediment sources. Average differences in provenance predictions between the different tracer groups in lake, reservoir and floodplain sediment cores were lowest in the reservoir core at 19% and highest in some floodplain cores, with differences in predictions in excess of 50%. In these latter samples organic enrichment of t

Published
2014

15. Analysis of acid deterioration of leather

Author

Janssen, Elsje, Paris, Mariabianca, Sawicki, Malgorzata, Seymour, Kate, Thorn, Andrew, Lama, Anne, Antunes, A Paula M, Fletcher, Yvette, Guthrie-Strachan, Jeffry, Vidler, Karen, Janssen, Elsje, Paris, Mariabianca, Sawicki, Malgorzata, Seymour, Kate, Thorn, Andrew, Lama, Anne, Antunes, A Paula M, Fletcher, Yvette, Guthrie-Strachan, Jeffry, and Vidler, Karen

Published
2010

16. The impact of beamhouse processes on bacterial growth

Author

Lama, Anne, Allen, Stuart C H, Attenburrow, Geoff E, Bates, Margaret P, Covington, Anthony D, Antunes, A Paula M, Lama, Anne, Allen, Stuart C H, Attenburrow, Geoff E, Bates, Margaret P, Covington, Anthony D, and Antunes, A Paula M

Abstract

Various bacterial species including potential pathogens have been isolated from hides and skins. During conventional leather processing, due to the extreme environmental conditions, the probability of bacteria surviving on hides is reduced. Alternatively, total or partial replacement of the hazardous chemicals with nonhazardous chemicals during best available technologies (BAT) processes may provide suitable conditions for bacterial growth. The aim of the present work was to determine the effect of conventional and BAT beamhouse operations on certain bacterial species. Decontaminated calf skin samples were inoculated with a known bacterial species found in hides or skins. A conventional and BAT beamhouse processes was carried out with inoculated skin samples, and bacterial growth was determined at various stages of beamhouse through microbial analysis. Analysis of the bacteria during the beamhouse operations showed that some of the stages of the beamhouse process inhibited the bacterial growth whilst other stages promoted the growth of bacteria.

Published
2009

17. Interview for: The East Midlands Nanotechnology Roadshow - Nanowhat? Totally Tiny Technology

Author

Antunes, A Paula M and Antunes, A Paula M

Abstract

A series of films commissioned by The University of Nottingham (on behalf of all the universities of the East Midlands) to explain to the wider population what nanotechnology is and what it can do for us, making science interesting and engaging to children and adults. It communicates difficult concepts in a visually stimulating way.

Published
2008

18. The interaction between collagen hydrogels with fibroblast cells

Author

Duan, Yonggang, Antunes, A Paula M, Attenburrow, Geoff E, Paul, Gordon, Duan, Yonggang, Antunes, A Paula M, Attenburrow, Geoff E, and Paul, Gordon

Abstract

Introduction - Collagen hydrogel is a 3D matrix which is able to emulate the natural environment of the connective tissue in the human body. It can be used as a basic material to investigate the interaction of fibroblast cells with matrices in vitro. It is difficult to measure the attachment, growth and migration of cells on these matrices. However, this study attempted to quantify the attachment, growth and migration of fibroblast cells on collagen hydrogel as well as their physical effect. Methods - Collagen hydrogel was prepared using collagen, Dulbecco’s modified Eagles medium and phosphate buffer at neutral PH. The attachment of fibroblast cells from human skin on collagen hydrogel and collagen membrane was compared. The migration of fibroblast cells was observed by monitoring their migration to a hydrogel matrix in the medium. An MTT assay [tetrazolium-based (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)] was used for the quantification of fibroblast growth over a 4-day period. Hydrogel contraction, due to fibroblast growth, was also quantified. Results and discussion - The number of adhered fibroblast cells on the collagen hydrogel and collagen membrane was found to be more than without collagen. The results suggested that collagen membrane and collagen hydrogel were conducive to fibroblast attachment. Fibroblast cell growth occurred on the collagen hydrogel during the incubation period. The collagen hydrogel started to contract from the second day with a larger contraction ratio occurring at days 2 and 3, thereafter the contraction stabilized and came to a halt after 10 days. Larger contraction was observed in the collagen hydrogel due to higher cell proliferation when compared with the hydrogel without cells

Published
2005

19. Investigation of novel deep eutectic systems for the reduction of water usage in leather manufacture

Author

Abbott, Andrew P., Antunes, A. Paula M., Jeffry Guthrie-Strachan, Keib Mmapatsi, and William Wise

Abstract

Water in the wet processes of leather manufacture acts as a solvent, transportation medium, support system and is an integral component of the collagen matrix stability at the macro and molecular levels. There have been proposals as to what extent water can be substituted with non-aqueous media, partly due to its role in collagen and processing. As the water content increases from bulk to float water, the system acts as a transport medium for chemical as well as a support system in processing vessels. Here, Deep Eutectic Solvents (DES) are investigated as an alternative solvent system to conventional tanning systems. The novel solvent is non-aqueous, has a high solubility for metal salts, low toxicity, is readily biodegradable and operates at variable temperatures without the release of harmful vapours. These properties make the DES system a potential alternative in leather processing, improving reagent uptake with the potential of lowering effluent discharge. The research focuses on the role of the solvent associated with stabilising collagen, such as the influence of inter- and intra-fibrillar, as well as bulk water, using type 2 DES systems. Thermal, mechanical analysis and electron microscopy were undertaken to determine the effects of the solvent system. The studies indicated that the solvent used, as well as the choice of counter ion, have an important effect on the thermal and mechanical stability of collagen.

20. Microscopic examination of skin structure

Author

Wertheim, D., Covington, Anthony D., nick petford, Tom Murray, and Antunes, A. Paula M.

Subjects
integumentary system
Abstract

Microscopic examination of the skin structure may help in identifying possible lesions as well as studying the integrity of the tissue; two dimensional examination of the structure may not be able to easily identify the complexity of the collagen bundle network in skin sections. In this area our research involves examination of skin sections in three dimensions. Thin dermal sections were stained with Haematoxylin and Eosin (H & E) and mounted on glass slides with a cover slip. The sections were imaged using a Leica TCS SP2 confocal microscope (Leica Microsystems GmbH, Germany). We have developed software techniques for 3D visualisation of the confocal data allowing display on a computer monitor or an observation cube. The image shows an example of visualisation from confocal microscope data of collagen bundles in a skin section (microscope image width 750 microns).

21. Parameters for composting tannery hair waste

Author

Arthur Onyuka, Margaret Bates, Attenburrow, Geoff E., Covington, Anthony D., and Antunes, A. Paula M.

Subjects
integumentary system, otorhinolaryngologic diseases
Abstract

Solid hair waste is generated by the leather industry as a by-product of the leather manufacturing process. Keratin, the main structural constituent of hair proteins, is highly resistant to degradation and their disposal is of environmental concern. The aim of this study was to develop conditions favorable for the degradation of bovine hair in a composting environment as an environmentally friendly option for the management of solid tannery hair waste. The thermophilic optimum temperature, 40 – 50C, moisture content 55%, pH 7.0 and a carbon to nitrogen ratio of 35:1 were found to be favorable to sustain metabolic functions of thermophilic microbial flora, responsible for degrading keratins. The biodegradation and structural transformation of the substrate was assessed using scanning electron microscopy. The results show that under these conditions the bovine hair lost most of its integral structural stability and that the cuticular components were more resistant to degradation. The compost stability as evaluated by monitoring the degree of humification and carbon to nitrogen ratio indicated that the final product achieved reasonable stability by attaining 73% degree of humification, 26% humification rate and carbon to nitrogen ratio of 29:1. Hence the composting technology used in this study has potential application in the leather industry for the production of an economically viable product

22. Precipitation of mixed metal residues from wastewater utilising biogenic sulphide

Author

Bhagat, Mamta, Burgess, Joanna E., Antunes, A. Paula M., Whiteley, Chris G., and Duncan, John R.

Subjects
*PRECIPITATION (Chemistry), *METALS, *INDUSTRIAL wastes, *SULFIDES
Abstract

Conventional metal extraction processes leave residual metals in solution which are lost as pollutants in process wastewaters. Biogenic sulphide precipitation is applied successfully to processes for the extraction of base metals and sulphates from solution, and may also be applicable to the low concentrations found in wastewater streams. Experiments were performed to precipitate metals out of synthetic wastewater by sparging with biogenic sulphide gas and by mixing with sulphide rich supernatant from a sulphate-reducing bioreactor. The composition of the metal precipitates generated was investigated. Metal removal from wastewater sparged with biogenic H2S(g) varied depending on the metal and the ratio of metal:sulphide. Maximum removal efficiencies were 30% for iron and 100% for gold and copper. Mixing the bioreactor supernatant with the metal solutions achieved 100% iron, 96% gold and 99% copper removal. The precipitates produced comprised mainly metal sulphides, but also contained unidentified complexes which may include nitrates, chlorides and carbonates. [Copyright &y& Elsevier]

Published
2004
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23. Exploring fine sediment dynamics and the uncertainties associated with sediment fingerprinting in the Nene river basin, UK

Author

Pulley, Simon, Foster, Ian D. L., and Antunes, A. Paula M.

Subjects
551.48, GB1201 Rivers. Stream measurements, QE571 Sedimentation and deposition
Abstract

To comply with the European Union Water Framework Directive (2000), National Governments are required to achieve good chemical and ecological status of freshwater bodies. Fine sediment has been shown to be a major cause of the degradation of lakes and rivers, and as a result research in geomorphology has been directed towards the understanding of fine sediment dynamics. It was identified by a review of published literature that at present a paucity of information on sediment dynamics existed for the East Midlands, UK. The use of tracers within a sediment fingerprinting framework has recently become a heavily used technique to investigate the sources of fine sediment pressures. However, uncertainties associated with tracer behaviour have been cited as major potential limitations to sediment fingerprinting methodologies. At present few studies have quantified the uncertainties associated with tracer use, or the exact reasons why different tracers are producing different sediment provenance results. This thesis had two aims based on these gaps in published literature. First, to assess the impact of sediment sampling methodology, tracer selection, particle size corrections and organic enrichment corrections on a fine sediment fingerprinting study. Secondly, to develop a partial sediment budget for the Upper Nene river basin and its major tributaries. The results of this thesis were presented in two parts. The first part investigated Aim 1 when fingerprinting; historically deposited sediment, suspended sediment and recently deposited sediment. The second part investigated Aim 2 by constructing a fine sediment budget for the Nene river basin, consisting of; sediment yield, sediment provenance, floodplain sediment accumulation and channel bed sediment storage. A mean difference of 24.1% between the predicted contributions of sediment originating from channel banks was found when using nine different tracer groups to fingerprint the river sediment samples. When fingerprinting contributions from urban street dusts mean differences between tracer group predictions were lower, at between 8% and 11%. There was little indication that organic matter content and / or particle size caused differences between tracer group predictions. Within-source variability in tracer concentrations, and small contrasts between the tracer concentrations of the sediment source groups, were identified as probable causes of inherent uncertainty present in the fingerprinting analysis. It was determined that the ratio of the percentage difference between median tracer concentrations in the source groups and the average within-source tracer concentration coefficient of variation could indicate the likely uncertainty in model predictions prior to tracer use. When fingerprinting historically deposited sediment, a reservoir core was fingerprinted with the least uncertainty, with tracer group provenance predictions ~28% apart and with consistent down-core trends. When fingerprinting an on-line lake core and four floodplain cores, differences between tracer group predictions were as large as 100%; the down-core trends in changing sediment provenance were also different. The differences between tracer group predictions could be attributed to the organic matter content and particle size of the sediment. There was also evidence of the in-growth of bacterially derived magnetite and chemical dissolution affecting the preservation of tracer signatures. Despite the prior indications that organic matter and particle size were causing tracer non-conservatism in historical sediment cores, data corrections were found to often be ineffective at reducing the differences between tracer group predictions. The corrections were found to either have no effect on, or increase the mean differences between, tracer group predictions when fingerprinting river sediment. The sediment budget identified that the annual sediment yield of 13 - 19 t km-2 yr-1 for the Nene is low in comparison to other UK catchments. Channel banks were found to be the dominant sediment source in the Nene, typically contributing between 60% and 100% of the sediment. Rates of sediment accumulation on the Nene’s floodplain was found to be highly variable (920– 7,200 t km-2 yr-1); the presence of flood defences were likely to be a cause of this variability, and have caused a reduction in the accumulation rate since 1963. It was found that large quantities of sediment accumulated on channel beds during periods of low flows (~ 28% of the annual sediment yield), which was flushed from the bed by a series of flood events (leaving <1% of the annual sediment yield in temporary storage). An original contribution to research was made by quantifying the uncertainties associated with tracer use in a fine sediment fingerprinting investigation, as well as identifying the probable causes of the observed uncertainty. The fine sediment dynamics of the Nene basin were also investigated for the first time, and it was identified that the high contributions from channel banks in the Nene were highly a-typical for UK catchments.

Published
2014

24. The impact of the leather manufacturing process on bacterial growth

Author

Lama, Anne and Antunes, A. Paula M.

Subjects
628.4, TD896 Industrial and factory wastes, TS967 Chemistry and science of leather, TS965.5 Tanning, QR75 Bacteria
Abstract

Hides and skins used as a raw material for leather manufacture may be contaminated with various microbial species including potential pathogens. Many bacterial species such as Bacillus, Staphylococcus, Micrococcus and Pseudomonas were isolated from raw hides/skins, and hides/skins at different stages of leather making process. The extreme environmental conditions present during a conventional tanning process due to hazardous chemicals may prevent the growth of bacteria present on hides/skins. On the other hand, partial or total replacement of the hazardous chemicals with non-hazardous chemicals, during a best available technologies (BAT) process, may provide suitable conditions for microbial growth in tannery effluent and hides/skins. Therefore, the aim of the project was to determine the survival and growth of the various bacterial species during the conventional and BAT leather-making processes. The beamhouse and tanning stages were studied, as the majority of the environmental pollution occurs during the early stages of the leather making process. Both the pre-soaking and soaking stages during the conventional and BAT leather-making processes provided suitable conditions for bacterial (Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus spp.) growth and proliferation. The results showed a significant reduction in the number of B. cereus found during the conventional and BAT unhairing processes. Limited B. cereus growth was observed during the subsequent reliming process. Bacillus cereus growth also occurred during the deliming and bating processes (conventional and BAT), followed by a decrease during the conventional and BAT pickling processes. No B. cereus colonies were isolated during the chrome tanning process. Growth of P. aeruginosa was inhibited during both the unhairing and reliming stages of the conventional and BAT leather making processes. A reappearance and recovery of P. aeruginosa in the subsequent deliming and bating (conventional and BAT) processes, indicated that deliming and bating processes may provide suitable growth conditions for P. aeruginosa. On the other hand, both the conventional and BAT pickling processes, and the chrome tanning processes hindered P. aeruginosa growth. Staphylococcus spp. were present throughout the conventional and BAT leather-making processes. A large reduction in the number of Staphylococcus spp. was observed during the unhairing and reliming processes (conventional and BAT). Growth of Staphylococcus spp. occurred during the subsequent deliming, bating, pickling and chrome tanning stages for both the conventional and BAT leather-making processes. The biochemical assays for bacterial identification confirmed the presence of B. cereus, P. aeruginosa and Staphylococcus spp. during the leather processing. The pulsed-field gel electrophoresis (PFGE) method of DNA fingerprinting confirmed that the bacterial species isolated during the leather manufacturing processes were the inoculated B. cereus and P. aeruginosa, and no alteration of the DNA of above-mentioned bacteria occurred during the processing. Overall, the research showed that bacterial species are capable of surviving during both the conventional and BAT leather-manufacturing processes. The bacterial species prefer the environmental conditions during the pre-soaking and soaking processes, while the unhairing and reliming processes did not favour the growth of bacterial species. Bacterial colonies were enumerated during the deliming and bating processes indicating that the unhairing and reliming processes did not cause total destruction of the bacterial cells. Alternatively pickling and chrome tanning processes were found to have suppressed the growth of bacterial colonies.

Published
2010

25. Extraction, characterisation and application of gelatin from chrome-tanned leather waste

Author

Martínez de Luna, Mercedes Catalina and Antunes, A. Paula M.

Subjects
600, TS967 Chemistry and science of leather, TS965.5 Tanning, TD1020 Hazardous substances and their disposal, TD794.5 Recycling
Abstract

The most significant problem of the tanning industry is waste generation. The presence of chromium in leather waste represents a potential hazard due to the possibility of Cr(III) being converted to its toxic state, Cr(VI). The treatment of chrome-tanned leather waste described in this research occurs in three phases: dechroming; isolation of gelatin, and application of the gelatin produced in the finishing of leather. Chrome-tanned shavings were dechromed and subsequently used for the production of gelatin. Gelatin was isolated from dechromed shavings in a one-step process, through thermal and chemical hydrolysis, using the hydrolytic agents ammonia, sodium hydroxide and acetic acid. The gelatin obtained through thermal hydrolysis exhibited better properties, in terms of gel strength, melting point, swelling and thermal properties, than the gelatin obtained through chemical hydrolysis and the former process was more cost-effective in terms of time, chemicals and waste production. The use of gelatin may be limited by its poor mechanical properties. The introduction of chemical modifications, using the crosslinking agents glutaraldehyde (GTA), oxazolidine II, ethylene glycol cliglycidyl ether (epoxy compound), hexamethylene dii socyanate (HMDC) and I -ethyl-3 -(3 -dimethylaminopropyl) carbodiimide (EDC), improved the performance in terms of strength and stability of the gelatin: oxazolidine and ethylene glycol diglycidyl ether are the most suitable since they confer plasticising properties in addition to stabilising the gelatin. A plasticiser (glycerol) was added into the matrix network of gelatin, increasing its flexibility. The isolated gelatin and a mixture of gelatinlglycerol were compared in use as a replacement for the commercial protein binder, casein, for glazed finishing. The finishing formulations were crosslinked with epoxy compound and oxazolidine. Physical tests carried out on the finished product showed promising results, with the gelatin/epoxy formulation showing potential for application. Ihe potential fbr gelatin isolated from chrome shavings to he produced as a high-added value material lor new applications in the future, such as a component tor finishing Formulations in the leather industry, was demonstrated

Published
2007

26. An investigation of the effects of crosslinking of collagen on cell/collagen-matrix interaction

Author

Duan, Yonggang and Antunes, A. Paula M.

Subjects
600, R857.T55 Tissue engineering, RD93 Wounds and injuries, QP552.C6 Collagen
Abstract

Wound dressing plays an important role in wound recovery and collagen interacts with the human body in such a way that it has specific advantages compared to synthetic materials. The aim of the present study was to get an optimal crosslinking agent for collagen and so the mechanical, chemical and biochemical properties of crosslinked collagen materials were investigated. Fibroblast cells are important in the process of wound healing, so the interaction of human fibroblast cells with crosslinked collagen films were investigated as well. Collagen I was isolated from bovine achilles tendons and collagen films were formed using the isolated collagen I solution. Collagen films were crosslinked with glutaraldehyde (GA), genipin, hexamethylenediisocyanate (HMDC), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) at the equal concentration of 0.02 M and these crosslinked collagen films were compared with uncrosslinked collagen films (control). The surfaces of the crosslinked films were investigated using scanning electron microscopy (SEM). There was observable fibre structure on GA- and genipin-crosslinked collagen films. The tensile strength, elongation at break and low strain modulus of the crosslinked collagen films were investigated. The results showed that GA-, genipin- and HMDC-crosslinked collagen films obtained higher tensile strength than the control. Elongation at break of all the crosslinked collagen films became lower than the control. GA- and genipin-crosslinked collagen films obtained higher low strain modulus than other crosslinked collagen films and the control. The denaturation temperatures of all crosslinked collagen films were significantly higher than the control and the denaturation temperatures of GA- and genipin-crosslinked films were much higher than those of HMDC- and EDC-crosslinked films. All the crosslinked collagen films were resistant to the digestion of collagenase. These results suggest that all the crosslinking agents are effective and GA- and genipin-crosslinked films obtained more extensive crosslinking. The interaction of crosslinked collagen films with fibroblast cells was investigated, e.g. adhesion, proliferation and migration of fibroblast cells. The results demonstrated that the control, genipin- and EDC-crosslinked collagen films were conducive to cell adhesion. Fibroblast cells on the control, genipin- and EDC-crosslinked collagen films were able to proliferate after 24 hours, with increased growth after 48 hours. The fibroblast cells on the control, genipin- and EDC-crosslinked collagen films migrated directionally. The cells on genipin-crosslinked film initiated directional migration earlier than those on control- and EDC-crosslinked films. In summary, genipin crosslinked collagen films show high denaturation temperature, higher tensile strength and good biocompatibility for fibroblast cells adhesion, proliferation and migration. Genipin should be regarded as a suitable crosslinking agent for reconstituted collagen for use in wound dressing.

Published
2007

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