- Temperature Measurement during Millisecond Annealing: Ripple Pyrometry for Flash Lamp Annealers.
- Migrants, Minorities & Health: Historical and Contemporary Studies (Routledge Studies in the Social History of Medicine).
- Hellenism in Late Antiquity;
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Industrial Biotransformations. The completely revised second edition of this user-friendly and application-oriented overview of one-step biotransformations of industrial importance. Based on extensive literature and patent research, this book is unique in arranging each process in a systematic way to allow for easy comparison. All the chapters have been rewritten, with all the processes updated and more than 30 new processes added. Each set of data is accompanied by key literature citations, supported by flow sheets where available, reduced to their significant elements.
In addition, an extensive index classified by substrates, products, enzymes, and companies provides direct access to each process, organized according to enzyme class. Overcoming the existence of well-developed traditional technology however is an inherent challenge to biotransformation processes. Often there is no financial incentive for implementing a new process when old technology is known and investment in plants have been paid for Faber and Franssen It is unlikely therefore that biotechnology will automatically replace existing chemical technology, unless of course compounds of choice cannot be made by chemical means or process economics are dramatically in favour of the new process.
Twenty to thirty years ago there were high expectations for biotechnology and many saw it as the technology of the future. Some of these expectations have not materialised as anticipated, but as can be seen from the examples discussed there is great scope for biotransformation processes. However, biological and process solutions do exist to many of these problems and methods to compare strategies and techniques for biotransformation operation are being developed Lilly , Woodley and Lilly Table 1 summarises the principle advantages and disadvantages of biotransformations compared with traditional chemical processes.
Table 1: Advantages and disadvantages of biotransformation and bioconversion processes.
Industrial Biotechnology Second Semester Syllabus for MSc Biotechnology & MSc Microbiology
It has not just been the market-pull but also the technological-push that has made biotransformations a viable substitute for conventional chemical synthesis Table 2. These technological advances can best be described as two areas; the biocatalyst and biochemical engineering. The term biocatalyst can refer to enzymes in various forms ie. Arnold has looked at methods of enhancing biocatalysis by enzyme engineering and similarly the industrial applications of protein engineering have been discussed by Recktenwald et al.
However the biggest advance in biotransformation operation has to be recombinant DNA technology. Not only is it possible to over express particular genes but it is also possible to express them in another organism, or to create unique catalysts. For example, a plasmid containing genes over expressing trehalase has been inserted into Escherichia coli.
The enzyme accumulated in the periplasm of the Escherichia coli and this made it easy to extract it by osmotic shock Tourinho-dos-Santos et al. It is now anticipated that within a few years more than half the world's enzymes will be produced commercially using recombinant DNA technology Lilly More recently it has been shown that enzyme crystals grown and crosslinked with a bifunctional agent eg glutaraldehyde exhibit higher kinetic tolerance to high temperatures, near-anhydrous organic solvents and mixed aqueous - organic solvents than both soluble and conventionally immobilised enzymes St.
Clair and Navia It is coming to the stage now where the biochemical engineer will be able to describe the characteristics of the preferred biocatalyst and the molecular biologist will be able to produce it. It was the technology to extract intracellular enzymes on a large scale Hetherington and the subsequent biocatalyst immobilisation that made biotransformation an alternative to chemical synthesis. Prior to the advent of large scale high-pressure homogenisation it was only extracellular enzymes or those extracted by chemical lysis that could be used for biotransformation.
Immobilisation techniques allow the water soluble enzymes to be recovered and reused in a solid form.
Industrial Biotransformations, 2nd, Completely Revised and Enlarged Edition
Lilly and Katchalski-Katzir have presented good reviews of the advantages and disadvantages of biocatalyst immobilisation, the successes and the failures. Immobilisation of the biocatalyst, enzyme or whole cell, is not only carried out for processing reasons but also used to modify enzyme properties, and to alter and regulate cell product formation Clarke Often useful chemistry involves reactants and products that are poorly water-soluble and from this evolved the techniques to operate biotransformations in organic solvents Tramper and Vermue The organic phase can be the sole liquid phase, or part of a two-liquid aqueous - organic phase system.
In the latter case the organic phase can be the reactant eg. The addition of a second organic liquid phase has also allowed kinetically unfavourable reactions to be carried out eg. A summary of the general thermodynamics of multiphase systems has been presented by Halling and Woodley and Lilly have discussed the process engineering aspects of operating a two-liquid phase biotransformation. One of the earliest biotransformation processes to employ immobilised enzyme technology was the production of high fructose glucose syrups, by glucose isomerase, which has been operating now since High fructose glucose syrup is used in the soft drinks and confectionary industries as it has health advantages over the conventional sugar, sucrose fructose is twice as sweet, lower in calories and not absorbed into the bloodstream as quickly as sucrose.
More than 8 x tonnes of high fructose glucose syrups are produced annually.
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On a smaller scale but a higher value product , 7. This process, using the immobilised penicillin acylase, amidase has been operational since These examples show that biotransformations can be efficient and commercially competitive. Biotransformations are being used in speciality chemical manufacture of flavours and fragrances Cheetham again in the area where only one isomer or stereo isomer has the required biological activity and the other is inactive or has undesirable activity.
Also only L -monosodium glutamate has taste enhancing properties and only L -menthol out of eight isomers has the desired combination of mint taste and cooling sensation. The role of biotransformation technologies in the flavours and fragrances industry are becoming more prominent and not just for the ability to produce single enantiomers.
There is an increasing demand by consumers for natural, environmentally friendly and healthy products, made from natural, renewable sources; for use in both food ingredients and in personal care products. As modern market demand for these "natural" products increases so there is a decline in the availability of traditional raw materials eg. A biotransformation process has now been developed for Ambrox 7 which is one of the most important aroma components of ambergris a naturally occurring excretion product of the sperm whale Cheetham It is in this area, the production of "natural products" that holds potential for New Zealand industries.
The use of biotransformation techniques in New Zealand has principally been limited to the primary industries meat and dairy industries. This is illustrated by Table 3 which highlights the uses of biocatalysts in New Zealand industries.
Work at Industrial Research Limited Stevenson has looked at the use of an immobilised lipase to produce a tallow derivative enriched with monoglyceride. Monoglycerides are used as emulsifiers in food and cosmetics and as antistaling agents in bread. Immobilised lipases can also be used to rearrange fatty acids in triglycerides and to modify the composition of the fat Stanley and Armstrong Therefore potentially it will be possible to produce tasty, monosaturated oil from tallow or to make tallow less prone to raise cholesterol levels when used in cooking MacKenzie and Stevenson New Zealand Pharmaceuticals Limited manufactures bulk pharmaceuticals and fine chemicals from a range of natural raw materials eg.
Steroid transformation work by biocatalysis in relation to the bile acid production facility has proved successful, but unfortunately at the time there was no commercial application Maddox Table 3: Biotransformation processes used commercially in New Zealand information taken from Kennedy and Davies Biocatalyst Use Company protease used to produce food additives, infant formula and cell growth media for the pharmaceutical industries, from dairy based materials NZDRI and dairy companies lipase modify and add value to milkfat based products ie.
In the dairy industries, the utilisation of enzymes and microorganisms has had a vast impact in the areas of cheese starter technology, cheese ripening and the modification and enhancement of cheese flavour products by lipase addition Coolbear and Holland Other research in this area has concentrated on the enzymic modification of milk fat and milk proteins, lipase catalysed milkfat for concentration of flavours and the production of natural dairy emulsifiers Ravenhall and Davies, personal communication.
The advantages of using biotransformations for these types of reactions is the ability to operate under mild conditions, hence retaining the traditional properties of the dairy products. Enzymes that can remove "sticky dextrins" during baking have also been investigated at Food and Crop Research Every Another use of biotransformations, the use of microorganisms in the treatment of sewerage and waste water, has been used for many years.
Recent advances have seen the use of enzymes and genetically engineered bacteria for biological waste water treatment processes Freeman and Fullerton At the Waste Technology Research Centre in Otago, research has focused on the use of biocatalysts in the degradation of toxic compounds and pollutants.