The nematocidal agent, Tsukamurella paurometabola C-924, was cultured in a 300 l bioreactor. Spray-dried formulations of this microorganism were prepared using sucrose. At an outlet temperature 62 degrees C, survival rates between 12 and 85% were reached with sucrose up to 10% (w/w). The stability study of the powders showed that the best storage condition was at 4 degrees C under vacuum. A new method for the calculation of cell death order for bacteria stored at low temperatures was developed. Powders stored under vacuum showed an Arrhenius behavior in relation to cell death kinetics.
A new method for the rapid estimation of viability in anhydrobiotic cells of the biocontrol agent Tsukamurella paurometabola C-924 was developed. The method is based on the absorbance due to hydrogen sulfide production. A linear model was obtained by plotting decimal logarithm of the corrected absorbance at 670 nm (log[Abs corrected ]) versus the decimal logarithm of culturable cells (log[X v ]) (r 2 = 0.9428). After comparing the results obtained by the proposed method to the ones obtained by the plate counting technique, no significant difference was observed in the number of culturable cells. The new technique, which is faster than plate counting, permits the estimation of biologic activity in anhydrobiotic cells of the strain C-924 in only 2 h.
PRACTICAL APPLICATIONSNo previous reports concerning the method presented in this paper were found in the reviewed literature; in our particular case, this method allows a rapid evaluation of the viability and physiologic state of Tsukamurella paurometabola C-924. The method presented here permits the estimation of viability in desiccated cells of bacteria that produce hydrogen sulfide from cysteine as a sulfur source. This methodology could be applied in research related to the isolation of anhydrobiotes hydrogen sulfide producers. In addition, industrial application could be found, for example, the assessment of the 3 Corresponding 222 viability of bacteria hydrogen sulfide producers formulated in wettable powders used in bioremediation or bioprecipitation of heavy metals. Furthermore, the biologic activity of these microorganisms could be estimated (i.e., desulfurase activity).
The release of transgenic organisms has evoked an unusual legal process in that laws governing it are prospective on perceived risks rather than retrospective on experienced risks as is the usual case with legislating against problems. Most countries undertaking transgenic releases have adopted a regulatory structure usually comprising controlled releases to address questions of perceived risks followed by uncontrolled commercial releases. There has been an increasing number of commercial releases from approximately 11 million hectares of transgenic crops in 1997 to more than 27 million hectares in 1998. Most of these commercial releases have been in industrialized countries with only a small proportion in developing countries. The controlled releases, together with laboratory experiments, have addressed a range of perceived risks which can be put into three groups: risks to humans and domesticated animals, risks tO the environment, and commercial risks. These perceived risks have to be assessed against the baseline of current and projected farming practices with non-transgenic crops. Few, if any, of these perceived risks have been shown to be real risks which are significantly more important than the non-transgenic situation. The situation with plants transgenically protected against virus infection was discussed. In some countries, the discussions on transgenic crop releases have entered the public domain. The debate has raised various ethical issues and reflects the wish of society to be involved in the adoption of new technologies. [L]
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