Scielo RSS <![CDATA[Electronic Journal of Biotechnology]]> vol. 4 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<B>Biotechnology and Development</B>: <B>A balance between IPR protection and benefit-sharing</B>]]> <![CDATA[<B>Biotechnology and Human Development in Developing Countries</B>]]> <![CDATA[<B>Environmental and Industrial Biotechnology in Developing Countries</B>]]> <![CDATA[<B>Biotechnology, bioethics and the poor</B>]]> <![CDATA[<B>Biotechnology Issues in Africa</B>]]> <![CDATA[<B>Immobilization and stabilization of papain on chelating sepharose: a metal chelate regenerable carrier</B>]]> A method for immobilization of papain has been selected based on the interaction between its histidine, cysteine and tryptophan residues with the immobilized metal ion (IMI) carrier for maximum binding on a small volume of the carrier. The immobilized papain retained high activity has improved thermal stability and the carrier could be recovered from the spent bound enzyme, to be reused. Reimmobilization of papain on the regenerated matrix was equally effective with the retention of maximum enzyme activity. <![CDATA[<B>The release of light metals from a brown seaweed (<I>Sargassum</I> sp.) during zinc biosorption in a continuous system</B>]]> The biosorption of zinc and calcium was investigated with a biomass of Sargassum sp., a brown seaweed, in a continuous system consisting of three serial tubular fixed-bed laboratory reactors. Results indicated that zinc was efficiently recovered by the biomass. After treatment of 9.0 liters of a mixed solution containing 130.0 mg/l zinc and 260.0 mg/l calcium, the first column of the system saturated with zinc; the remaining columns did not saturate with zinc as a result of the pre treatment performed by the first reactor. Calcium was also efficiently biosorbed by the biomass, saturating the system much faster than zinc. X-ray fluorescence spectrum indicated the presence of various elements in the structure of the Sargassum sp. biomass, especially alkaline and alkaline-earth elements. Alkaline and alkaline earth elements played a key role in the biosorption of zinc, being responsible for ion-exchange reactions performed during zinc biosorption. <![CDATA[<B>Analysis of Uruguayan weedy rice genetic diversity using AFLP molecular markers</B>]]> Weedy rice is a serious problem in Uruguayan rice fields since intensification of rice production started about 10 years ago. The genetic diversity of 26 weedy accessions of weedy rice and 6 Uruguayan cultivars were analyzed using AFLP (amplified fragment length polymorphisms) methodology. Abundant polymorphisms were found among samples tested. Using different methods of analysis three groups of samples were revealed. A relationship was found between three groups and morphological traits. One group had a black hull, purple apex and long awn (wild type traits) while another group had straw hull and apex, and short or no awn (domestication traits). The third group included the cultivars analyzed and some weedy rice samples. The weedy rice in this third group is presumed to most closely mimic cultivated rice and may have recently evolved. The results suggest that weedy rice adapts either to the natural environment or to cultivation. The former type with black hull and long awn may be easy to control because it can easily be seen. The later group may be difficult to control, particularly since the weedy rices within the cluster consisting of cultivars suggest that weedy rices are continually evolving in Uruguayan rice fields. The AFLP technique is very effective for assessing genetic diversity within weedy rice and will be very useful for fingerprinting of local cultivars of rice. <![CDATA[<B>The effect of protective ingredients on the survival of immobilized cells of <I>Streptococcus thermophilus</I> to air and freeze-drying</B>]]> Streptococcus thermophilus cultures were grown either on trehalose or lactose, immobilized in alginate beads, dipped in various protective solutions and dried by either convection air-drying (CAD) or freeze-drying (FD). Immobilized cultures dipped in the 0.1% peptone solution did not show good survival to CAD or FD, as mortality was over 99%. There was no significant difference in mortality levels, in both methods of drying, when lactose or trehalose were used as protective ingredients. The highest survival levels (50 to 98%) were with a whey-sucrose protective medium, but this was potentially related to a higher pH and solids of the solution. Mortality levels were higher in FD than CAD, and this did not appear to be related to the fact that FD cultures had lower residual moisture contents than those dried under CAD. Cells grown on lactose had slightly higher survival rates to drying than those obtained from CAD. Trehalose-positive and trehalose-negative cultures of S. thermophilus did not show different mortality patterns to CAD or FD. <![CDATA[<B>Molecular dynamics simulations of active site mutants of rat liver arginase</B>]]> By using molecular dynamics (MD) simulations and crystallographic data for rat liver arginase, the substrate positions in the active sites of native and mutant forms of the enzyme, were compared and correlated with known kinetic consequences of mutations. The mutants compared were His 141<IMG SRC="/content/vol4/issue3/full/6/flecha2.gif" WIDTH=12 HEIGHT=9>Phe and His 141<IMG SRC="/content/vol4/issue3/full/6/flecha2.gif" WIDTH=12 HEIGHT=9>Asn. The simulations show that mutation His141<IMG SRC="/content/vol4/issue3/full/6/flecha2.gif" WIDTH=12 HEIGHT=9>Asn gives the greatest divergence from the atomic coordinates, when compared with the control native enzyme. The mutant Asp128<IMG SRC="/content/vol4/issue3/full/6/flecha2.gif" WIDTH=12 HEIGHT=9>Asn does not show a change in atomic coordinates in the substrate, in agreement with the concept that a change in the metal coordination is responsible for the loss of catalytic activity in this mutant. Results obtained agree with reported kinetic consequences of mutations in arginase. <![CDATA[<B><I>Trichoderma aureoviride</I> 7-121, a mutant with enhanced production of lytic enzymes:</B>: <B>its potential use in waste cellulose degradation and/or biocontrol</B>]]> A mutant of the native fungus Trichoderma aureoviride, 7-121, selected for its overproduction of extracellular cellulase and ß-glucosidase (cellobiase) was obtained. In shake flask cultures, production of endoglucanase, filter paper activity and cellobiase increased two to four- fold as compared with the wild type strain. The mutant strain is stable and grows rapidly in liquid as well as in solid culture media. Enzyme yields were best when pH was controlled so that it did not fall bellow pH 3.5. Cellobiase production by this mutant is particularly high (approximately 5 U/ml) as compared to other Trichoderma, strains, which makes it a suitable candidate for waste cellulose degradation. In addition, the mutant strain showed enhanced production of fungal cell wall degrading enzymes: chitinases, ß-1,3-glucanases and proteases. This improvement in extracellular enzyme production by the mutant T. aureoviride 7-121 suggests that it is a suitable strain to be used in biological control. <![CDATA[<B>Plant genomics and agriculture</B>: <B>From model organisms to crops, the role of data mining for gene discovery</B>]]> Sequencing and analysing of the Arabidopsis thaliana genome, the first plant kingdom genome to be unraveled, will always remain a scientific landmark. International initiatives to sequence rice, the most important cereal in Asia, are underway. However as functional information piles up in Arabidopsis and rice, researchers working in other crops will benefit from this new knowledge and apply it to their studied plants or crop species. The increasing role of public databases of model organisms and bio-informatics in data mining, presents a new opportunity as well as a challenge to researchers to develop more focused molecular tools for gene discovery and deployment. The work presented in here describes how such an approach has benefited sorghum, a rainfed semi-arid troprical cereal.