Manufacturing

In the manufacturing sphere, it seems certain that there will be increasing pressures to continue the reductions in pollution and waste production. These are related issues, of course, and both may be addressed by one of two general approaches: a priori methods to avoid the problem in the first place or a posteriori to clean it up more efficiently after the event. Clean production methods, which have been variously discussed in Chapters 4 and 10, seem likely to play a growing part in achieving the former. The use of various production biotechnologies will limit the environmental impact of ever more industrial processes by reducing their energy demands, the strength of effluents generated, the amount of waste requiring ultimate disposal and so on. The growing importance of biocatalysis, and the general use of biological macromolecules in manufacturing procedures will, inevitably, lead to the development of novel and innovative techniques for many substances currently generated by conventional means. There are many candidates for the forthcoming major roles in the bioindustrial production cycles of the near future but probably amongst the most revolutionary and beneficial are likely to be found amid the ranks of the extremophiles, which were previously discussed in Chapter 3. Extremozymes isolated from these bacteria and archaea, which dwell happily in some of the most unlikely and biologically challenging of environments on the planet, offer the potential to catalyse reactions previously the exclusive realm of physical chemistry. Their potential lies both in primary action and secondary effect. The first of these utilises enzymes obtained to bring about the desired effect, where such specificity of action is a natural characteristic of the donor microbe. Secondary effects arise by virtue of the elucidation of the functionally key features of naturally occurring substances. This allows the same mechanisms to be incorporated into artificial chemicals which subsequently achieve a goal for which no direct analogue exists in nature. In this respect, for instance, further study of extremozymes isolated from hyperthermophilic organisms may well permit the mechanism of their heat tolerance to be discerned and the appropriate means incorporated into other, non-natural catalysts.

The value of the extremozyme contribution has already been noted in the now well-established PCR technique, which enabled a major jump ahead to be made in the whole science of biotechnology itself. In addition, the commercial use of an enzyme obtained from another thermophile to increase the efficiency of cyclodextrin production from cornstarch is a currently known example of clean technology. Though these compounds are valued in the pharmaceutical and food industries, where they principally aid the stabilization of volatile ingredients, the process can still fairly be said to have an environmental component. Improved manufacturing efficiencies typically go hand in hand with reduced pollution, waste production or energy demand. In the future, this aspect of industrial activity seems set to assume far greater importance and extremophile research may well provide many of the necessary tools to make it possible.

Thus, hyperthermophilic extremozymes have potential applications in many industries, offering amylases for confectionary or alcohol production, proteases for amino acid production, baking, brewing and detergents, xylanases for paper bleaching, and dehydrogenases and oxidoreductases for a variety of commercial uses.

In the chemical industry, the possible use of whole-organism hyperthermophiles offers new ways to produce hydrogen, methane and hydrogen sulphide. At temperatures between 18-80 °C and under anaerobic conditions, this latter gas, for example can be made by Desulfuromonas from elemental sulphur. The conventional chemical catalysis system requires a temperature of 500 °C or more to yield the same result. Unsurprisingly then, the potential of whole-cell microbial biocatalytic methods and their notably superior specificity, is viewed with great interest. In future, it may be possible to redesign the configuration of conventional bioreactors to produce efficient, high temperature substitutes for many of the currently standard industrial processes.

Other extremophiles could also have roles to play. Psychrophiles may yield enzymes which will function at the low refrigerator temperatures typically required to avoid spoilage in food processing, for enhanced cold-wash 'biological' washing powders and in perfume manufacture, reducing evaporative fragrance losses. A use has been suggested for halophile enzymes in increasing the amount of crude oil extracted from wells, though whether this will ever be a commercial reality remains to be seen and, moreover, leaves aside any consideration of the 'environmental' aspects of increased fossil fuel extraction. Acidophilic extremozymes may one day form catalysts in chemical syntheses in acid solution, and alkaliphile derived proteases and lipases may replace existing versions in washing detergents to enhance their action. In addition, some of the textile industry's enzyme-using processes may see alkaliphilic extremozymes replacements for greater efficiency.

However exciting the prospects of extremophile use may be, turning their potential into industrially deliverable processes will not be straightforward. For one thing, many of these organisms are found in very specific and specialised ecological niches and replicating their optimum environmental requirements is likely to prove difficult, particularly within bioreactor systems initially designed around mesophile cultivation. Hence, new types of reactors and, possibly, novel solid-state fermentation techniques may need to be developed before this can be achieved. Commercial-scale cultures of extremophiles for extremozyme harvesting is also likely to prove problematic, since by virtue of their habitats, it is rare to find large numbers of any given single species in nature. For such purposes, the isolation and purification of the required microbial culture to be grown up is generally both difficult and costly to do. Though the extremozymes can be produced using recombinant DNA methods, as were discussed in Chapter 9, avoiding the need for wholesale, mass culturing of the extremophiles themselves, any industrial attempt at whole organism biocatalysis will, of course, demand it.

Despite the clear biotechnological potential of extremophile clean manufacturing, a complete comparison between these emergent technologies and conventional methods will inevitably be required before they are likely to gain mainstream industrial acceptance. There is no doubt that they have advantages, but issues like cost and guaranteed reliability will prove vital in their uptake.

Clean manufacturing as a field appears to have a major contribution to make to the environmental cause and there are a number of possible novel manufacturing biotechnologies emerging. Particularly when implemented alongside 'green' chemical processes, they promise significant advances in pollution reduction over the coming years.

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