Scielo RSS <![CDATA[Electronic Journal of Biotechnology]]> vol. 2 num. 1 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<B>STABILITY OF BIOCATALYSTS</B>]]> Biocatalysts are inherently labile; therefore their operational stability is of paramount importance for any bioprocess. The problem of biocatalyst stability has been tackled from different perspectives, which are reviewed in the present paper. Inherently stable biocatalysts are well appreciated and a systematic effort is being done in the search of new organisms that harbor them. The potential of extremophiles has recently been recognized. Moreover, cloning such termophilic genes into more suitable mesophilic hosts is now at hand to produce stable biocatalysts. Another approach is to use site-directed mutagenesis to code for more stable proteins. A relevant number of actual industrial biocatalysts are being produced using such genetic and protein engineering tools. Operational stabilization of biocatalysts is an alternative. Immobilized and crystallized biocatalysts are stable forms already in use. Also engineering the reaction media can contribute to biocatalyst stabilization. This is a key factor for using enzymes in organic synthesis where non-aqueous media are mandatory or at least highly desirable. Bioreactor design requires sound expressions to describe biocatalyst inactivation under operation conditions. Unfortunately, most information has been gathered in non-reactive situations, which poorly describe actual behavior. Models are proposed to consider the presence of substrate and products on biocatalyst stability and thus describe properly bioreactor performance. <![CDATA[<B>Technological Strategies of Successful Latin American Biotechnological Firms</B>]]> This paper presents the results of the analysis of the technological strategies of eight Latin American biotech firms. There is little literature on strategies of follower firms in developing countries in high-technology sectors. For that reason, the authors undertook case studies of firms of six countries of Latin America that share the characteristics of being successful in the market place while adopting technology-follower strategies. The analysis considers five dimensions that, according to the literature on the management of technology, constitute the basic benchmarks of the strategy. These dimensions include innovating activities of the firm to improve, its position on the market; orientation of research and dominant technological goals; technology sources used by the firm to acquire its critical technologies; level of technological investments to acquire and/or develop technologies; and organizational mechanisms to manage technological functions of the firm. Results of this study clearly show that Latin American firms can sustain competitive strategies on the intelligent management, combining in-house skills with excellent capabilities to locate, acquire and assimilate external technologies. <![CDATA[<B>Feasible biotechnological and bioremediation strategies for serpentine soils and mine spoils</B>]]> Reclamation of metalliferous areas is a priority field of biogeochemistry of trace elements. Ultramafic outcrops rich in heavy metals have been mapped in different parts of the world. Heavy metals are potentially cytotoxic, caricinogenic and mutagenic. Environment protection agencies and legislations insisting the mine operators to restore the mine spoils and tailings since the metal leachates have serious implications in production of healthy agricultural products. Hence, restoration of mine spoils, tailings and metalliferous soils is a challenging task for the well being of Humans. Synthetic and natural zeolites have been used as chelators for rapid mobility and uptake of metals from contaminated soils by plants. Use of synthetic chelators significantly increased Pb and Cd uptake and translocation from roots to shoots facilitating phytoextraction of the metals from low grade ores. Contrastingly, synthetic cross linked polyacrylates, hydrogels have protected plant roots from heavy metals toxicity and prevented the entry of metals into roots. However, application of these synthetics on large scale may not be a practical solution due to exorbitant costs. Therefore, introduction of metal tolerant wild plants to metalliferous soils, genetic engineering of plants for enhanced synthesis and exudation of natural chelators into the rhizosphere, improvement of the rhizosphere with the help of mycorrhiza and integrated management of the metalliferous ecosystem following the principles of phytoremediation are discussed in this paper. <![CDATA[<B>DEVELOPMENT OF A MOLECULAR MARKER FOR RUST RESISTANCE GENES Sr39 AND Lr35 IN WHEAT BREEDING LINES</B>]]> Polymorphic DNA bands were identified between a near iso-isogenic line of wheat carrying both stem (Sr39) and leaf (Lr35) rust resistance genes and the recurrent line Thatcher (Tc) which lacks these genes. Both resistance genes are located on a translocated chromosomal segment derived from Aegilops speltoides and thus are genetically linked. The primers used to generate polymorphic bands were 3'-anchored inter-simple sequence repeat primers which identified genomic microsatellites with a repeated motif of 3 nucleotides in length. The primers were used singly to amplify genomic segments which were flanked by inversely orientated, closely spaced, identical microsatellite sequences. One of the polymorphic bands, a 900 base pair band, was completely linked to the Sr39 and Lr35 rust resistance genes in the segregating population used in this study. After cloning and sequencing this polymorphic band, the inter-simple sequence repeat marker was converted to a sequence characterized amplified region marker by designing primer sets which amplify a single, easily resolved band from DNA of plants with Sr39/Lr35 genes. This marker is present in six wheat lines carrying the Sr39 and Lr35 genes on the translocated chromosome segment from Ae. speltoides. The marker has facilitated efforts to breed Canada Prairie Spring and Canada Western Extra Strong lines with these rust resistance genes <![CDATA[<B>Sequence variability in p27 gene of Citrus Tristeza Virus (CTV) revealed by SSCP analysis</B>]]> Citrus tristeza closterovirus (CTV), is a phloem-limited virus transmitted by aphids in a semipersistent manner. The genome of CTV is composed of a ssRNA with two capsid proteins: CP, covering about 95% of the particle length, and a diverged coat protein (dCP), present only in one end of the particle, forming a rattlesnake structure. dCP is the product of p27 gene for which it is also postulated a function in the transmissibility by aphid vectors. Hybridization analysis showed a p27 gene region, which exhibits different patterns with two probes derived from two biological distinct CTV isolates. In an attempt to screen whether that gene region differs in mild and severe strains, six CTV isolates belonging to different biogroups were compared for variations in their p27 gene by analysis of single-strand conformation polymorphism (SSCP). The p27 gene was reverse transcribed and amplified by PCR and thirty clones of each isolate were obtained. From each clone, two fragments of the gene were amplified by PCR: fragment (a), 459 bp long, and fragment (b), 281 bp long. Sequence variations in both gene fragments were studied by SSCP analysis. A variety of SSCP patterns was obtained from each isolate, being isolates belonging to the groups II-IV and III those with the higher and lower number of them. Moreover, SSCP analysis provided a rapid procedure to screen the genetic heterogeneity of the viral isolates reducing considerably the amount of nucleic acid sequenciation necessary to gain that knowledge.