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Problems still inherent in food-industry biocatalyst sustainable-deployment?
Trends in Food Science & Technology 15 (2004) 276–279
Short communication
Problems still inherent in foodindustry biocatalyst sustainabledeployment? Alan Wisemana and Len Woodsb a
c/o Molecular Toxicology Group, School of Biomedical & Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK b Woodside Consulting, 14a The Spinney, Camberley, Surrey GU15 1HH, UK
Industrial biocatalyst deployment strategies would benefit from an approach that supersedes mere choice and immobilization of naturally-occurring enzymes (protein effectors and enablers). Further investigation is necessary, ‘real-lab’ and in silico, to identify inherent inhibitors, protein-protectors (chaperones) and also acceptable synzymes (enzyme-mimics) that meet ‘generally recognized as safe’ criteria. In developing the early 21st Century laudable aspiration of ‘‘multifunctionality’’, many foods will be enhanced by harnessing the benign abilities of dissolved or insoluble (immobilized) naturally-occurring enzymes, present or added. Now the utilization of safe synzymes (enzyme mimics) is sought (Tucker & Woods, 1997) whilst accepting that most mimics will need metal ions (Tucker & Woods, 1997; Wiseman, Lewis, Ridgeway, & Wiseman, 2000) to work in those cases where redox reactions are necessary for acceptable conversion rates. For instance, powdered iron will catalyse the rapid conversion of hydrogen peroxide to water and oxygen: but catalase (Fe) enzyme does it circa 105 times faster. 0924-2244/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2003.11.001
Immobilized enzymes (IME) and immobilized cells (IMC) have now a proven track record of success, having prevailed in a 40-year campaign for their utilization in industry: insoluble IME and IMC in use at present are effectively retained and therefore are excluded from our diet or pharmaceuticals; unlike soluble enzymes or non-immobilized micro-organisms or other cells. The temptation persists nevertheless for a switch to inexpensive ‘tailor-made mimics’ to facilitate particular bioprocesses. The benefits of avoidance, for example, of critical-temperature biocatalyst burnout might follow the adoption of fully thermostable soluble mimics such as synzymes (enzyme-like); or of analogues with identified similar mechanistics, rather than features of structural similarity. However, one should beware of the introduction of undesirable odours/flavours in branded products as this could lead to expensive re-imaging and market re-targeting. However, products of such optimized bioprocess-facilitation strategies could come to be viewed as undesirable foods, if perceived to confer only a lesser nutrient/health benefit value. It would be unfortunate if some designer-foods were to follow the pitfall of other nutritious foods of becoming targeted because of their reputation as ‘best-avoided’ (in consumer perception)! This problem is exacerbated by ready acceptance of dysfunctionality/multifunctionality ratio index estimates for risk/benefit assessment approaches. Moreover, nutrigenomics- and nutriproteomics-based ‘just-over-the-horizon’ predictions should not be ignored (see Fig. 1). Although initial commitment to convert to enzymic bioprocessing of foodstuffs may have been agreed, it would be prudent nevertheless to seek to identify the most appropriately novel enzyme-catalysed bioconversions that might be deemed to be desirable in the planned food-bioprocessing initiative (Wiseman, 1995; Wiseman, Lewis et al., 2000). The proposed bioprocess may seemingly defy prediction of worthwhile deployment of purified biocatalysts, however, for a number of reasons, as follows. These reasons may include, inter alia, the unavoidable presence of enzyme (or mimic) inhibitors; and pH-optimum or critical temperature incompatibility, within multienzyme operations. The latter can be dependent therefore on the rate-limiting slow step. Thus, the second enzyme in the serial process may need to be present in 40 excess over the first enzyme (to drive the overall
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
277
Fig. 1. Unsustainable ‘fail-clean’ food bioprocess association with poor retention of multifunctional food-components within the processed food: circumvention of eratic outcomes due to absence of equilibrated-precipitation (this causes errors in product-harvest optimum scheduling that leads to the resolubilization of precipitates).
reaction fast forward) away from the substrate/product equilibrium position overall at that temperature. Moreover, there will be diffusion-limitation manifest on the observed catalytic constant (kcat/Km) of enzymes immobilized to inappropriate supports: especially in particular types of bioreactor (stirred tank, fixed bed or fluidized bed) (Palmer, 2001; Wiseman, Goldfarb, Ridgeway, & Wiseman, 2000). Km is raized and kcat is lowered in most cases of immobilized enzymes; if under diffusion-limitation. In some cases, such problems can be readily circumvented by well-established adjustments to support-charge, and through enzyme stabilization by active-site-spared cross-linking conformational constraint with glutaraldehyde. Enzyme stabilization can be achieved also by addition of protective agents, such as thiols; to achieve heavy metal removal by liganding (Lewis, 2001). Furthermore, overcoming these problems (rather than mere attainment of practical circumvention) is now achievable by construction of recombinant DNA designer enzymes. If these enzymes are used in covalentbond immobilized form (to solid supports) a no-residue
outcome can be guaranteed in the food or pharmaceutical when marketed. Bioprocessing of foods (Wiseman, Lewis et al., 2000) using, inter alia, novel enzyme-mimics, analogues or synzymes should be approached with due caution, therefore, to seek to avoid product dysfunctionality for some consumers due to their idiosyncratic ‘nutrigenomics’ (see on). This is in contrast to the expected multifunctionality arising from the addition of healthbenefiting biomolecules such as vitamins and other antioxidants (these accommodate the public expectation of protection from disease and ageing) (Wiseman, 1995). The next generation of routinely added enzymes in food-bioprocessing is likely to include many natural redox-enzymes (but they generate reactive oxygen species, ROS) (Palmer, 2001; Wiseman, Goldfarb, Ridgeway, & Wiseman, 2000). These can now be readily selected from the circa 2700 isoforms of the cytochromes P450 (EC 1.14.14.1) ubiquitous family of mixed function oxidases (mono-oxygenases) (Tucker & Woods, 1997; Wiseman, Lewis, Ridgeway, & Wiseman,
278
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
2000) — Homo sapiens has 57 of these. Furthermore, added cytochrome P450 enzyme operates normally as the terminal electron acceptor protein (electron sink) of a redox-protein chain (starting at NADPH/NADH): except in bacteria, this is cytochrome P450 reductase (flavoprotein, with a second electron supplied by cytochrome b2) (Lewis, 2001; Wiseman, Lewis et al., 2000). Up to now, most bio-aids to clean food-processing have employed hydrolase enzymes, such as a wide range of proteases, amylases, lipases and hemicellulases. These enzymes remove proteins, starch, fats and hemicellulose, respectively: thus, they lower the viscosity of complex, usually aqueous, solutions; which saves on the cost of electrical pumping. Many sophisticated approaches are now emergent that lead to a raising of the estimated nutraceutical status (multifunctionality/dysfunctionality index) of bioprocessed foods (Wiseman & Woods, 2001) to deliver the long-term health benefits predicted. Moreover, most isoforms of cytochromes P450 are detoxifying agents that increase the hydrophilicity of many dietary toxins of plant origin (Wiseman, Lewis et al., 2000; Wiseman & Woods, 2002; Lewis, 2001). Oxygen insertions achieve this biomolecular conversion and the hydroxylated toxicants produced (and consumed)
are more likely to be readily excreted through the kidney (usually after further glucuronidisation in the liver) (Lewis, 2001): or in the faeces if biliary-gut recirculation is significant. Nevertheless, the temptation to supersede selected naturally-sourced plant, microbial and animal enzymes with synzymes (enzyme-mimics) must proceed with appropriate caution in the case of food bioconversions (Wiseman, Lewis et al., 2000). This is because most synzymes contain metal complexes that are included to seek to replicate the mechanistic chemistry of the chosen enzyme. For example, cytochromes P450 contain iron, and this metal is not a problem: but there may be less consumer confidence in the safety of, for example, ruthenium present in some mimicing complexes of this enzyme. Other acceptable liganded-metals in foodstuffs can include some copper (Wiseman & Woods, 2002), zinc, manganese, cobalt, magnesium, calcium, sodium, potassium, vanadium (Opara, 2002) and chromium (Opara, 2002). It is noteworthy that selenium is beneficial at 50 mg per day but it is rather toxic at 500 mg per day (Rayman, 2002) (this metal is therefore a benemin: good for you only in small doses). Dietary Se is necessary
Table 1. Impact of untimely food-bioprocessing that leads to perceived dysfunctionality Unit-operation stage
Mode of food-overtransformation
Deleterious outcomes of problems
Decolouration: too rapidly
Enzymic or chemical over-bleaching
ROS causes phospholipid membrane oxidation
Viscosity-lowering hysteresis: mixing problems
Overloading with hydrolases: enzymes or mimics
Biocatalyst residues: if were not used in immobilized form. Also two-phase separation.
Soft-texturing of tough foods
Overuse of proteases or mimics
‘Steak’ replaced by ‘soup’ after softening procedures
Oxygen transfer rate (OTR): variation in oxygen mass transfer coefficient (kLa)
Over-activity of oxygenases: such as by some of 2700 isoforms of cytochromes P450 possibly present
Bioconversions diverted towards dysfunctional-component formation or retention
pH-control
Over-adjusted with acids or bases
Unwanted discolouration or flavour change
Temperature-control
Overshoot and ‘critical temperature’ exceeded for enzymes
Failure of endogenous or added enzymes
Mixing-control
Complete homogeneity not appropriate
Foaming, overheating
Gas recycle-control
Over-removal of functional gases
Fine limits of O2/CO2 removal exceeded
Immobilization of biocatalyst
Undesirable leakage from IME of enzymes and metals
Food contamination
Downstream processing
Loss of taste, odour, texture
Failure of toxicant removal down to fine limits
Effluent recycle to seek to lower the BOD
Developoment of unwanted odours and tastes
Loss of nutraceutical components
IMC-stage
Prolonged fermentation
Over-production of secondary metabolites such as lactate
IME, immobilized enzyme; IMC, immobilized cells; ROS, reactive oxygen species; BOD, biological oxygen demand.
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
to form active glutathione peroxidases (they remove peroxide). In addition, superoxide anion .O/2 (free radical, a reactive oxygen species (Wiseman, Goldfarb et al., 2000) is removed in the body by cytosolic Cu/Zn superoxide dismutase (Wiseman & Woods, 2002) (Mn/superoxide dismutase is present in mitochondria). Hydrogen peroxide is removed by catalase (this contains Fe). Cobalt is the cofactor metal in vitamin B12. Nevertheless, potential for leakage of metal ions from their liganded-sites in mimics and enzymes, and other proteins, may necessitate monitoring; where particular metals are considered to require benchmarking standards. For example, the level of tin in canned foods has become limited (to 5 ppm). In addition, the level of selenium above about a beneficial level of 200 mg per day could be worthy of scrutiny; as some individuals may be mildly intolerant to selenium at below the 500 mg per day dietary threshold usually quoted (see above) (Rayman, 2002; Wiseman, 2003a, 2003b, 2003c, 2003d, 2003e; Wiseman & Woods, 2003)—see Table 1.
References Lewis, D. F. V. (2001). Guide to cytochromes P450 structure and function. London, UK: Taylor & Francis. Opara, E. C. (2002). Oxidative stress, micronutrients, diabetes mellitus and its complications. Journal of the Royal Society of Health, 122, 28–34. Palmer, T. (2001). Enzymes: biochemistry, biotechnology, clinical chemistry. Chichester, UK: Horwood Publishing.
279
Rayman, M. (2002). Se brought to earth. Chemistry in Britain, 38, 28–31. Tucker, G. A., & Woods, L. F. J. (1997). Enzymes in food processing (2nd ed.). Glasgow, Scotland, UK: Blackie & Sons. Wiseman, A., Lewis, D. F. V., Ridgway, T. J., & Wiseman, H. (2000). Cytochromes P-450 in food-processing: limitations of imitations. Journal of Chemical Technology and Biotechnology, 75, 3–5. Wiseman, A. (Ed.). (1995). Handbook of enzyme biotechnology (3rd ed.). Hemel Hempstead, UK: Ellis Horwood, (Prentice Hall). Wiseman, H., Goldfarb, P., Ridgway, T., & Wiseman, A. (2000). Biomolecular free radical toxicity: causes and prevention. Chichester, UK: John Wiley & Sons. Wiseman, A., & Woods, L. F. J. (2001). Precautions against immobilized enzyme (IME) inhibitors. Trends in Food Science & Technology, 12, 469–470. Wiseman, A., & Woods, L. F. J. (2002). Welcome praise for copper. Chemistry in Britain, 38, 20. Wiseman, A. (2003a). Problems with enzyme bioprocessing of foodstuffs. Trends in Food Science & Technology, 14, 109–110. Wiseman, A. (2003b). Nutraceutical bioprocessing to supersede food technology? Trends in Food Science and Technology, 15, 44–45. Wiseman, A. (2003c). Limitations of in silico predictability of specificity of co-immobilized cytochromes P450 and mimics in foodbioprocessing. Biotechnology Letters, 25, 515–519. Wiseman, A. (2003d). Replacement of immobilized cell bioreactors by smaller immobilized enzyme bioreactors: unique outcome predictability for cytochromes P450 isoforms? Biotechnology Letters, 25, 1581–1590. Wiseman, A. (2003e). Novel cytochromes P450 applications from the directed-evolution of recombinant micro-organisms. Letters in Applied Microbiology, 37, 1–4. Wiseman, A., & Woods, L. F. J. (2003). Safe choice of metals in food bioprocess enzyme mimicry. Trends in Biotechnology, 2, 7–8.
Any Suggestions? Articles published in TIFS are usually specially invited by the Editors, with assistance from our International Advisory Editorial Board. However, we welcome ideas from readers for articles on exciting new and developing areas of food research. A brief synopsis of the proposal should first be sent to the Editors, who can provide detailed guidelines on manuscript preparation. Mini-reviews focus on promising areas of food research that are advancing rapidly, or are in need of re-review in the light of recent advances or changing priorities within the food industry. Thus they are shorter than conventional reviews, focusing on the latest developments and discussing likely future applications and research needs. Features are similar in style to mini-reviews, highlighting specific topics of broad appeal to the food science community. The Viewpoint section provides a forum to express personal options, observations or hypotheses, to present new perspectives, and to help advance understanding of controversial issues by provoking debate and comment. Conference Reports highlight and assess important developments presented at relevent conferences worldwide. TIFS also welcomes Letters to the Editor concerned with issues raised by published articles or by recent developments in the food sciences. All Review-style articles are subject to editorial and independent peer review by international experts in the appropriate field.
Short communication
Problems still inherent in foodindustry biocatalyst sustainabledeployment? Alan Wisemana and Len Woodsb a
c/o Molecular Toxicology Group, School of Biomedical & Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK b Woodside Consulting, 14a The Spinney, Camberley, Surrey GU15 1HH, UK
Industrial biocatalyst deployment strategies would benefit from an approach that supersedes mere choice and immobilization of naturally-occurring enzymes (protein effectors and enablers). Further investigation is necessary, ‘real-lab’ and in silico, to identify inherent inhibitors, protein-protectors (chaperones) and also acceptable synzymes (enzyme-mimics) that meet ‘generally recognized as safe’ criteria. In developing the early 21st Century laudable aspiration of ‘‘multifunctionality’’, many foods will be enhanced by harnessing the benign abilities of dissolved or insoluble (immobilized) naturally-occurring enzymes, present or added. Now the utilization of safe synzymes (enzyme mimics) is sought (Tucker & Woods, 1997) whilst accepting that most mimics will need metal ions (Tucker & Woods, 1997; Wiseman, Lewis, Ridgeway, & Wiseman, 2000) to work in those cases where redox reactions are necessary for acceptable conversion rates. For instance, powdered iron will catalyse the rapid conversion of hydrogen peroxide to water and oxygen: but catalase (Fe) enzyme does it circa 105 times faster. 0924-2244/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2003.11.001
Immobilized enzymes (IME) and immobilized cells (IMC) have now a proven track record of success, having prevailed in a 40-year campaign for their utilization in industry: insoluble IME and IMC in use at present are effectively retained and therefore are excluded from our diet or pharmaceuticals; unlike soluble enzymes or non-immobilized micro-organisms or other cells. The temptation persists nevertheless for a switch to inexpensive ‘tailor-made mimics’ to facilitate particular bioprocesses. The benefits of avoidance, for example, of critical-temperature biocatalyst burnout might follow the adoption of fully thermostable soluble mimics such as synzymes (enzyme-like); or of analogues with identified similar mechanistics, rather than features of structural similarity. However, one should beware of the introduction of undesirable odours/flavours in branded products as this could lead to expensive re-imaging and market re-targeting. However, products of such optimized bioprocess-facilitation strategies could come to be viewed as undesirable foods, if perceived to confer only a lesser nutrient/health benefit value. It would be unfortunate if some designer-foods were to follow the pitfall of other nutritious foods of becoming targeted because of their reputation as ‘best-avoided’ (in consumer perception)! This problem is exacerbated by ready acceptance of dysfunctionality/multifunctionality ratio index estimates for risk/benefit assessment approaches. Moreover, nutrigenomics- and nutriproteomics-based ‘just-over-the-horizon’ predictions should not be ignored (see Fig. 1). Although initial commitment to convert to enzymic bioprocessing of foodstuffs may have been agreed, it would be prudent nevertheless to seek to identify the most appropriately novel enzyme-catalysed bioconversions that might be deemed to be desirable in the planned food-bioprocessing initiative (Wiseman, 1995; Wiseman, Lewis et al., 2000). The proposed bioprocess may seemingly defy prediction of worthwhile deployment of purified biocatalysts, however, for a number of reasons, as follows. These reasons may include, inter alia, the unavoidable presence of enzyme (or mimic) inhibitors; and pH-optimum or critical temperature incompatibility, within multienzyme operations. The latter can be dependent therefore on the rate-limiting slow step. Thus, the second enzyme in the serial process may need to be present in 40 excess over the first enzyme (to drive the overall
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
277
Fig. 1. Unsustainable ‘fail-clean’ food bioprocess association with poor retention of multifunctional food-components within the processed food: circumvention of eratic outcomes due to absence of equilibrated-precipitation (this causes errors in product-harvest optimum scheduling that leads to the resolubilization of precipitates).
reaction fast forward) away from the substrate/product equilibrium position overall at that temperature. Moreover, there will be diffusion-limitation manifest on the observed catalytic constant (kcat/Km) of enzymes immobilized to inappropriate supports: especially in particular types of bioreactor (stirred tank, fixed bed or fluidized bed) (Palmer, 2001; Wiseman, Goldfarb, Ridgeway, & Wiseman, 2000). Km is raized and kcat is lowered in most cases of immobilized enzymes; if under diffusion-limitation. In some cases, such problems can be readily circumvented by well-established adjustments to support-charge, and through enzyme stabilization by active-site-spared cross-linking conformational constraint with glutaraldehyde. Enzyme stabilization can be achieved also by addition of protective agents, such as thiols; to achieve heavy metal removal by liganding (Lewis, 2001). Furthermore, overcoming these problems (rather than mere attainment of practical circumvention) is now achievable by construction of recombinant DNA designer enzymes. If these enzymes are used in covalentbond immobilized form (to solid supports) a no-residue
outcome can be guaranteed in the food or pharmaceutical when marketed. Bioprocessing of foods (Wiseman, Lewis et al., 2000) using, inter alia, novel enzyme-mimics, analogues or synzymes should be approached with due caution, therefore, to seek to avoid product dysfunctionality for some consumers due to their idiosyncratic ‘nutrigenomics’ (see on). This is in contrast to the expected multifunctionality arising from the addition of healthbenefiting biomolecules such as vitamins and other antioxidants (these accommodate the public expectation of protection from disease and ageing) (Wiseman, 1995). The next generation of routinely added enzymes in food-bioprocessing is likely to include many natural redox-enzymes (but they generate reactive oxygen species, ROS) (Palmer, 2001; Wiseman, Goldfarb, Ridgeway, & Wiseman, 2000). These can now be readily selected from the circa 2700 isoforms of the cytochromes P450 (EC 1.14.14.1) ubiquitous family of mixed function oxidases (mono-oxygenases) (Tucker & Woods, 1997; Wiseman, Lewis, Ridgeway, & Wiseman,
278
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
2000) — Homo sapiens has 57 of these. Furthermore, added cytochrome P450 enzyme operates normally as the terminal electron acceptor protein (electron sink) of a redox-protein chain (starting at NADPH/NADH): except in bacteria, this is cytochrome P450 reductase (flavoprotein, with a second electron supplied by cytochrome b2) (Lewis, 2001; Wiseman, Lewis et al., 2000). Up to now, most bio-aids to clean food-processing have employed hydrolase enzymes, such as a wide range of proteases, amylases, lipases and hemicellulases. These enzymes remove proteins, starch, fats and hemicellulose, respectively: thus, they lower the viscosity of complex, usually aqueous, solutions; which saves on the cost of electrical pumping. Many sophisticated approaches are now emergent that lead to a raising of the estimated nutraceutical status (multifunctionality/dysfunctionality index) of bioprocessed foods (Wiseman & Woods, 2001) to deliver the long-term health benefits predicted. Moreover, most isoforms of cytochromes P450 are detoxifying agents that increase the hydrophilicity of many dietary toxins of plant origin (Wiseman, Lewis et al., 2000; Wiseman & Woods, 2002; Lewis, 2001). Oxygen insertions achieve this biomolecular conversion and the hydroxylated toxicants produced (and consumed)
are more likely to be readily excreted through the kidney (usually after further glucuronidisation in the liver) (Lewis, 2001): or in the faeces if biliary-gut recirculation is significant. Nevertheless, the temptation to supersede selected naturally-sourced plant, microbial and animal enzymes with synzymes (enzyme-mimics) must proceed with appropriate caution in the case of food bioconversions (Wiseman, Lewis et al., 2000). This is because most synzymes contain metal complexes that are included to seek to replicate the mechanistic chemistry of the chosen enzyme. For example, cytochromes P450 contain iron, and this metal is not a problem: but there may be less consumer confidence in the safety of, for example, ruthenium present in some mimicing complexes of this enzyme. Other acceptable liganded-metals in foodstuffs can include some copper (Wiseman & Woods, 2002), zinc, manganese, cobalt, magnesium, calcium, sodium, potassium, vanadium (Opara, 2002) and chromium (Opara, 2002). It is noteworthy that selenium is beneficial at 50 mg per day but it is rather toxic at 500 mg per day (Rayman, 2002) (this metal is therefore a benemin: good for you only in small doses). Dietary Se is necessary
Table 1. Impact of untimely food-bioprocessing that leads to perceived dysfunctionality Unit-operation stage
Mode of food-overtransformation
Deleterious outcomes of problems
Decolouration: too rapidly
Enzymic or chemical over-bleaching
ROS causes phospholipid membrane oxidation
Viscosity-lowering hysteresis: mixing problems
Overloading with hydrolases: enzymes or mimics
Biocatalyst residues: if were not used in immobilized form. Also two-phase separation.
Soft-texturing of tough foods
Overuse of proteases or mimics
‘Steak’ replaced by ‘soup’ after softening procedures
Oxygen transfer rate (OTR): variation in oxygen mass transfer coefficient (kLa)
Over-activity of oxygenases: such as by some of 2700 isoforms of cytochromes P450 possibly present
Bioconversions diverted towards dysfunctional-component formation or retention
pH-control
Over-adjusted with acids or bases
Unwanted discolouration or flavour change
Temperature-control
Overshoot and ‘critical temperature’ exceeded for enzymes
Failure of endogenous or added enzymes
Mixing-control
Complete homogeneity not appropriate
Foaming, overheating
Gas recycle-control
Over-removal of functional gases
Fine limits of O2/CO2 removal exceeded
Immobilization of biocatalyst
Undesirable leakage from IME of enzymes and metals
Food contamination
Downstream processing
Loss of taste, odour, texture
Failure of toxicant removal down to fine limits
Effluent recycle to seek to lower the BOD
Developoment of unwanted odours and tastes
Loss of nutraceutical components
IMC-stage
Prolonged fermentation
Over-production of secondary metabolites such as lactate
IME, immobilized enzyme; IMC, immobilized cells; ROS, reactive oxygen species; BOD, biological oxygen demand.
A. Wiseman and L. Woods / Trends in Food Science & Technology 15 (2004) 276–279
to form active glutathione peroxidases (they remove peroxide). In addition, superoxide anion .O/2 (free radical, a reactive oxygen species (Wiseman, Goldfarb et al., 2000) is removed in the body by cytosolic Cu/Zn superoxide dismutase (Wiseman & Woods, 2002) (Mn/superoxide dismutase is present in mitochondria). Hydrogen peroxide is removed by catalase (this contains Fe). Cobalt is the cofactor metal in vitamin B12. Nevertheless, potential for leakage of metal ions from their liganded-sites in mimics and enzymes, and other proteins, may necessitate monitoring; where particular metals are considered to require benchmarking standards. For example, the level of tin in canned foods has become limited (to 5 ppm). In addition, the level of selenium above about a beneficial level of 200 mg per day could be worthy of scrutiny; as some individuals may be mildly intolerant to selenium at below the 500 mg per day dietary threshold usually quoted (see above) (Rayman, 2002; Wiseman, 2003a, 2003b, 2003c, 2003d, 2003e; Wiseman & Woods, 2003)—see Table 1.
References Lewis, D. F. V. (2001). Guide to cytochromes P450 structure and function. London, UK: Taylor & Francis. Opara, E. C. (2002). Oxidative stress, micronutrients, diabetes mellitus and its complications. Journal of the Royal Society of Health, 122, 28–34. Palmer, T. (2001). Enzymes: biochemistry, biotechnology, clinical chemistry. Chichester, UK: Horwood Publishing.
279
Rayman, M. (2002). Se brought to earth. Chemistry in Britain, 38, 28–31. Tucker, G. A., & Woods, L. F. J. (1997). Enzymes in food processing (2nd ed.). Glasgow, Scotland, UK: Blackie & Sons. Wiseman, A., Lewis, D. F. V., Ridgway, T. J., & Wiseman, H. (2000). Cytochromes P-450 in food-processing: limitations of imitations. Journal of Chemical Technology and Biotechnology, 75, 3–5. Wiseman, A. (Ed.). (1995). Handbook of enzyme biotechnology (3rd ed.). Hemel Hempstead, UK: Ellis Horwood, (Prentice Hall). Wiseman, H., Goldfarb, P., Ridgway, T., & Wiseman, A. (2000). Biomolecular free radical toxicity: causes and prevention. Chichester, UK: John Wiley & Sons. Wiseman, A., & Woods, L. F. J. (2001). Precautions against immobilized enzyme (IME) inhibitors. Trends in Food Science & Technology, 12, 469–470. Wiseman, A., & Woods, L. F. J. (2002). Welcome praise for copper. Chemistry in Britain, 38, 20. Wiseman, A. (2003a). Problems with enzyme bioprocessing of foodstuffs. Trends in Food Science & Technology, 14, 109–110. Wiseman, A. (2003b). Nutraceutical bioprocessing to supersede food technology? Trends in Food Science and Technology, 15, 44–45. Wiseman, A. (2003c). Limitations of in silico predictability of specificity of co-immobilized cytochromes P450 and mimics in foodbioprocessing. Biotechnology Letters, 25, 515–519. Wiseman, A. (2003d). Replacement of immobilized cell bioreactors by smaller immobilized enzyme bioreactors: unique outcome predictability for cytochromes P450 isoforms? Biotechnology Letters, 25, 1581–1590. Wiseman, A. (2003e). Novel cytochromes P450 applications from the directed-evolution of recombinant micro-organisms. Letters in Applied Microbiology, 37, 1–4. Wiseman, A., & Woods, L. F. J. (2003). Safe choice of metals in food bioprocess enzyme mimicry. Trends in Biotechnology, 2, 7–8.
Any Suggestions? Articles published in TIFS are usually specially invited by the Editors, with assistance from our International Advisory Editorial Board. However, we welcome ideas from readers for articles on exciting new and developing areas of food research. A brief synopsis of the proposal should first be sent to the Editors, who can provide detailed guidelines on manuscript preparation. Mini-reviews focus on promising areas of food research that are advancing rapidly, or are in need of re-review in the light of recent advances or changing priorities within the food industry. Thus they are shorter than conventional reviews, focusing on the latest developments and discussing likely future applications and research needs. Features are similar in style to mini-reviews, highlighting specific topics of broad appeal to the food science community. The Viewpoint section provides a forum to express personal options, observations or hypotheses, to present new perspectives, and to help advance understanding of controversial issues by provoking debate and comment. Conference Reports highlight and assess important developments presented at relevent conferences worldwide. TIFS also welcomes Letters to the Editor concerned with issues raised by published articles or by recent developments in the food sciences. All Review-style articles are subject to editorial and independent peer review by international experts in the appropriate field.