TIBTECH - JULY 1990 [Vol. 8] 169

Biosensors'. the state-of-the-art

Biosensors '90, the first world con- gress on biosensors* was distin- guished by a number of features from the numerous conferences encom- passing this topic over the past decade. In attempting to keep abreast of such a multidisciplinary subject as biosensors, one can quickly weary of the numerous conference venues and symposia volumes around. While it is obviously very valuable to interest a wide audience in the possibilities offered by biosensors, the specialist finds great difficulty in gleaning sufficient information from more general conferences. Biosen- sors '90 put the latest information from the principal laboratories in one place: with 183 peer-reviewed original papers from 31 countries, Biosensors '90 was the largest and most comprehensive event of its kind to date. (A selection of 30-40 refereed papers from the congress will appear in a special issue of the journal Biosensors and Bioelectronics.) The choice of an international and neutral location equidistant from the USA and Europe, Australia and Japan promoted international participation. A very high level of interest in the congress was apparent in Europe, which was home to 55% of the delegates. Some countries (for example, the FRG) enabled young as well as experienced workers to attend by instituting a competitive bursary scheme. Inevitably, how- ever, the audience consisted princi- pally of more senior representatives from academia (47%), industry (36%) and government/technology transfer organizations (17%).

* Biosensors '90, Mandarin Hotel, Singapore; 2-4 May 1990. Launched by Elsevier Seminars and supported by Cranfield Biotechnology Ltd. The second world congress on biosensors (Biosensors '92) is projected for May 1992.

Morning symposia (Affinity Sen- sors, Glucose Biosensors, Microbio- sensors and Flow Injection Analysis), presented by invited speakers, were followed by three parallel sessions of contributed papers, one of which continued the theme of the morning session, and the evening was given over to the poster sessions and general discussions. The consis- tently high quality of virtually all the presentations was reflected by the capacity audiences that attended every session.

The papers presented were gener- ally cautious and well argued, as befits a subject that is maturing into a more self-critical phase. Gone were the wild claims of the 1980s, to be replaced by a painful awareness of the reality of producing reliable analytical devices, simple and robust enough to operate under realistic conditions. In this respect, contributions from industrial labora- tories were particularly welcome. These provided a rare insight and some sobering lessons for industrial colleagues and academics alike. J. J. Johnson (YSI Inc., USA) followed a tribute to the man who started it all, Leland C. Clark Jnr, with a detailed history of the many pitfalls that befell YSI Inc. in their launch of the first commercial glucose biosensor and its successors. Johnson also revealed a link between YSI and A. Heller (University of Texas, USA), marking a notable departure for YSI away from hydrogen peroxide electrochemistry towards mediator- based technology. Prof. Heller pre- sented his work on mediator-modi- fied enzymes and polymer elec- trodes. The archetypal mediated enzyme electrode featured in I. J. Higgins' (Cranfield Institute of Tech- nology, UK) presentations, in which he described the evolution of the world's most successful biosensor to date, the ExacTech glucose sensor

~) 1990, Elsevier Science Publishers Ltd (UK) 0167 - 9430/90/$2.00

manufactured by MediSense (Boston, USA and Abingdon, UK). He went on to describe a wide range of me- diated amperometric devices includ- ing strategies for stabilizing devices for in vivo, and other, continuous applications.

Descriptions of pacesetting optical technology from Serono Diagnostics Ltd (Surrey, UK) and Amersham International PLC (Bucks., UK) were presented. Both companies have explored immunosensors based on surface plasmon resonance. G. Robinson (Serono Diagnostics Ltd) chose to focus on the virtues of their fluorescence capillary fill device while A. G. Evans (Amersham Inter- national PLC) emphasized the im- proved sensitivity achieved by using gold particles in conjunction with surface plasmon resonance. The introduction of a commercially suc- cessful immunosensor will undoubt- edly be a major step forward for the credibility of biosensors. Molecular Devices (California, USA) are al- ready marketing the light address- able potentiometric system and several companies are preparing to launch optical immunosensors in the near future.

Among the more academic presen- tations, F. Scheller's (Academy of Sciences, GDR) plenary lecture on second generation biosensors was particularly memorable. He compre- hensively reviewed the development of enzyme electrodes for glucose and placed recent advances in a clear context. Scheller traced the evol- ution of the enzyme electrode and highlighted the role of enzymatic stripping, analyte recycling and multifunctional sensing. Making in vivo measurements n o w was the theme adopted by P. T. Kissinger (Purdue University, USA) in his description of microdialysis. This technique delivers very small samples of buffer (equilibrated with the sample and protein flee) to the analytical instrument of choice. Work from the Max Planck Institute (FRG) using membrane proteins as low affinity receptors was described by H. Kiefer et el. They reported experiments with a lipid bilayer con- taining the H+: lactose cotransporter lactose permease that could be used to determine lactose by virtue of a pH sensitive fluorescent dye. Other highlights included K. Mosbach's (University of Lund, Sweden)

170 TIBTECH - JULY 1990 [Vol. 8]

glimpse into the future role of genetic and protein engineering in biosensor design, P. Bergveld's (University of Twente, The Nether- lands) meticulous analysis of protein related phenomena that could be used in immunosensing, the abun-

dance of work from Japan on micro- biosensors and a clearer view of current activities in China. By mentioning these few contributions, however, I do an injustice to the many other excellent invited and contributed presentations which

made this meeting so exceptional.

A N T H O N Y TURNER

Biotechnology Centre, Cranfield Institute of Techno]ogy, Cranfield, Bedford MK43 OAL, UK.

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Environmental biotechnology Environmental biotechnology was the topic for the first Annual Sym- posium of the European Environ- mental Research Organization (EERO)*. Dr Ken Timmis, chairman of the organizing committee and director of microbiology at the GBF, put together an outstanding program of 36 presentations highlighting recent developments from Europe and North America from the world's leading environmenta! biotech- nology laboratories.

Topics covered in the symposium included biodegradation mechan- isms, biosensors and biomonitoring, non-degradative biological activities for removal of pollutants, environ- mental catastrophe management, genetic approaches to strain improve- ment and predictability, ecology of pollution, environmental impact of bioremediation processes, and re- search and development priorities.

Those of us who chaired sessions highlighted particular reports in our areas of interest. My selection of especially exciting biodegradation studies follows.

Work by W. Francke and P. Fort- nagle (University of Hamburg, FRG) on microbial transformations of bi- arylethers, biarylketones, and related compounds was presented. They re- ported the isolation of Pseudomonas strains that regioselectively dioxy- genate the 1,2-positions of substi- tuted biarylethers and biarylketones. The Pseudomonas degraded bi- phenylether, xanthene, dibenzo- furan and dibenzo-p-dioxin. This

*Symposium on Environmental Bio- technology, Forschungsanstalt fi)r Land- wirtschaft (FAL), Braunschweig, FRG, 23-27 April 1990. [Symposium co- sponsored by FAL and Gesellschaft f~r Biotechnologische Forschung (GBF).]

last compound supported growth of the bacterium. I believe this is the first reported instance of microbial mineralization of the dibenzo-p- dioxin ring structure. The existence of such enzymes is encouraging to those who hope to use nature's gene pool to construct bacteria that degrade the highly toxic chlorinated dibenzo-p-dioxins contaminating many ecosystems. The initial re- actions catalyzed by enzymes of the dioxin degrader are shown in Fig. 1.

K. H. Engresser and H-J. Knack- muss (Institut ffir Mikrobiologie, Stuttgart, FRG) presented data con- firming this regioselective dioxygen- ation of biaryl- and cyclic biarylethers by bacteria. They showed that even some halogenated dibenzodioxins and dibenzofurans are attacked. Exciting advances!

T. Leisinger (Mikrobiologisches Institut ETH, Zfirich, Switzerland), L. Wackett (University of Minnesota, Gray Freshwater Biological Institute, Navarre, Minnesota, USA), and P. McCarty (Stanford University, Stan- ford, California, USA) reported several intriguing results from their studies of microbial degradation of chlorinated aliphatic hydrocarbons. They summarized the current state of knowledge concerning microbial degradation of compounds such as trichloroethylene (dechlorinated by a variety of bacterial oxygenases), chloromethane and dichloromethane (used as carbon/energy sources by some facultatively methylotrophic bacteria), trichloromethane (oxi- dized to formaldehyde, CO, and CO2 by methane monooxygenase), and carbon tetrachloride. This last com- pound was shown to be degraded to CO2 even by dead cells of various anaerobic bacteria. The responsible catalysts appear to be heat-stable cobalt-corrinoids or metallo-por-

~) 1990, Elsevier Science Publishers Ltd (UK) 0167 - 9430/90/$2.00

phyrins. McCarty presented evi- dence that most or all of the above processes can be encouraged to pro- ceed in situ within contaminated aquifers. Environmental biotech- nology is a maturing discipline, as proven by these three outstanding research groups.

R. L. Crawford (University of Idaho, Moscow, USSR), M. Salkinoja- Salonen (University of Helsinki, Finland), A. Bourquin (ECOVA Corporation, USA), R. Hfirzeler (Ciba Geigy AG, Switzerland) and M. Alexander (Cornell University, Ithaca, New York, USA) confirmed that the future for using microbial pure cultures or consortia is bright. Crawford described methods to dis- tribute and protect pollutant de- graders within contaminated aquifers by use of microsphere encapsulation techniques. Salkinoja-Salonen de- scribed her highly successful use of a Rhodococcus to remove chlorinated phenols from contaminated wood- treatment sites. Bourquin described a number of ECOVA's successful environmental Clean-up projects for compounds including phenoxy herbicides and mixed hydrocarbons. Hfirzeler and his associates have developed a process for using sulfate- reducing bacteria to degrade waste sulfuric acids. Finally, Alexander explained how we must define and understand the ecological constraints nature places on microbial commu- nities. In doing so, we may also learn how to overcome some of those constraints so that microbes can be used productively in the clean- up of our environment. Some of the priorities for environmental bio- technology research, identified by G. Omenn (University of Washing- ton, Seattle, USA) and Bourquin include:

• Demonstrating the effectiveness and economic feasibility of bio- remediation at a variety of real world sites.