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A Technical Guide for Wine Producers
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The Biotech Brief
To introduce this edition of the biotech brief, I would like to give feedback on current research relating to possible environmental concerns associated with GM crops. It is, however, important to remember that the objective of this column is not to argue for or against the use of GM crops, merely to communicate relevant information pertaining to local and international biotechnological research. As part of the scientific community's efforts to ensure the absolute safety of GM crops, a vast field study, involving hundreds of acres across Britain, was conducted over a period of three years to determine the possible effects of GM crops on the environment. Biotechnologists and environmental activists alike have eagerly awaited the results of this study, which, many hoped would put the GM issue to rest once and for all. Animal, insect and weed populations were monitored in fields of GM herbicide tolerant maize, beet and spring rape. The results of these trials were released in November 2003 but were, alas, at best inconclusive. In some cases, particularly in fields of GM beet and spring rape, some insect groups (like bees and butterflies) were less abundant than in their non-GM counterparts. This was attributed to less weeds and, therefore, less food and cover. There were also less weed seeds in GM beet and spring rape crops, seeds that are important dietary components of certain insect classes. In contrast, some groups of soil insects were found in greater numbers in GM beet and spring rape than in the non-GM counterparts. For herbicide tolerant GM maize, the scenario seemed to be reversed, certain groups of insects, as well as weed seeds were found in higher abundance than in the non-GM fields. A summary of the study can be found at the website: http://www.defra.gov.uk/news/2003/031016b.htm. According to the head of the research team, Dr. Les Firbank, "the results gave important new insights that will help conserve biodiversity within productive farm systems".
The results of these studies have also to be put into the broader context of technological development. The varieties tested are those that were developed several years ago, and correspond to crops with increased herbicide or increased inherent pest resistance. These crops were therefore designed to indirectly affect weeds and insects. However, biotechnological knowledge and know-how is increasing at a very fast rate, and very soon numerous other applications, including crops with increased health benefits or vitamin content will be released. It is unlikely that such crops would have similar impacts on their surroundings than those described above.
Reproducible fermentation remains one of the main challenges in modern day wine making. A major research objective within the oenological field still focuses on developing and breeding of new wine yeasts with improved fermentation capabilities. In this regard, the power of biotechnology really comes to the fore. We would like to highlight one of the success stories concerning the use of biotechnology, particularly the research of Drs, HJJ van Vuuren, H Volschenk and J Husnik that addresses some of the problems regarding malolactic fermentations. The author would like to thank Drs HJJ van Vuuren and H Volschenk for contributing this section. In the final section, Mr Wessel du Toit from the department of Viticulture and Oenology, Stellenbosch University, discusses some of the latest techniques used to determine the real time microbial status of filtered wine.
Genetically enhanced yeast to benefit consumers and producers
Most red wines and some white wines undergo the bacterial malolactic fermentation that catalyses the bio-conversion of L-malate to L-lactate. Some naturally occurring lactic acid bacterial strains in wine produce undesirable compounds, such as biogenic amines, from amino acids present in grape musts. The presence of bio-amines can be of great concern for consumers since these molecules, particularly histamine, have been shown to be the causative agent of headaches and other allergenic symptoms such as, diarrhoea, palpitations, rashes and vomiting. Moreover, strong scientific evidence suggests that other biogenic amines such as cadaverine, putrescine, spermine, and tyramine can potentiate the toxic effect of histamine. During the last two decades new technologies such as metabolic engineering, protein engineering, and novel enzyme and fermentation technologies have been developed that have greatly enhanced our capabilities to produce safer wines of a higher quality. The malolactic yeast ML01 is such an example. Over the last 10 years scientists in Dr. van Vuuren's laboratory have succeeded to genetically enhance an industrial wine yeast strain to perform the alcoholic and malolactic fermentations simultaneously. They have conducted rigorous scientific examination of the ML01 malolactic yeast and this yeast has now received Generally Regarded as Safe (GRAS) status from the FDA. The application of the ML01 malolactic yeast will minimize or prevent growth of lactic acid bacteria capable of producing allergens and at least ensure a reduction, or elimination, of these allergens from wine. This yeast will also have major benefits to wineries since it will eliminate sluggish and stuck malolactic fermentations resulting in spoilage of wines and improve colour in red wines substantially. This research was done in collaboration between the Wine Research Centre, University of British Columbia and the Department of Microbiology, Stellenbosch University. Any questions regarding this research can be addressed to Dr Hennie van Vuuren, email hjjvv@interchange.ubc.ca.
Counting the living
Following fermentation, microbial stability becomes a very important aspect of quality wine. Several "preservation" methods are employed to ensure microbial stability, including filtration and the addition of sulphur dioxide. Unfortunately, these methods do not always ensure absolute sterility. Techniques that can detect and distinguish between living and dead micro organisms can, therefore, be invaluable to minimize loss of quality as a result of unwanted microbial growth. Recently, a new technique that does exactly this has been used in a study to determine the effect of oxygen and sulphur dioxide on acetic acid bacteria as well as Brettanomyces-species. The technique, called epifluorescence, involves the treatment of filtered wine with a reagent that reacts exclusively with constituents in living cells. If excited by the right frequency light, the living cells fluoresce (much like a firefly!) and can be visualized under a microscope (Fig. 1). Higher fluorescence can also be attributed to healthier cells. The technique does require specialized equipment and is relatively expensive, therefore limiting accessibility to winemakers. It does, however, provide a fast way to distinguish dead from living cells and can be used in the enumeration of all wine micro organisms.
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