Scielo RSS <![CDATA[Electronic Journal of Biotechnology]]> http://www.scielo.cl/rss.php?pid=0717-345820090002&lang=es vol. 12 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<strong>Aerobic removal of stigmasterol contained in kraft mill effluents</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200001&lng=es&nrm=iso&tlng=es Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL’s maximum Chemical Oxygen Demand (COD) removal was 65%, whereas the Biological Oxygen Demand (BOD5) was around 95%. The removal efficiency of stigmasterol removal was 96% when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR. <![CDATA[<b>Estimation of phylogenetic relationships of <i>Phlomis</i> species based on seed protein polymorphism</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200002&lng=es&nrm=iso&tlng=es In this study, phylogenetic relationships among 39 Phlomis taxa were investigated based on seed protein profiles produced by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). A total of 21 polypeptide bands were scored, of which, 19 were polymorphic among the taxa of the genus Phlomis. A distance matrix was generated from the similarity matrix which was computed by using Jaccard’s similarity coefficients, based on polymorphic bands and then an UPGMA tree was established through cluster analysis performed on the distance matrix. Genetic distances ranged from 0.00 to 0.50 within subsection Dendrophlomis; from 0.00 to 0.625 within subsection Gymnophlomis and from 0.00 to 0.769 within subsection Oxyphlomis. The UPGMA tree formed four groups. The topology of the tree is in agreement with the taxonomic view regarding the section Phlomis as it is divided into three subsections as Dendrophlomis, Gymnophlomis and Oxyphlomis based on morphological characters. The grouping pattern of the tree also indicated that subsection Dendrophlomis is more closely related to subsection Gymnophlomis than subsection Oxyphlomis. <![CDATA[<b>Identification of QTLs for pod and kernel traits in cultivated peanut by bulked segregant analysis</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200003&lng=es&nrm=iso&tlng=es Bulked segregant analysis was used to identify simple sequence repeat (SSR) markers associated with pod and kernel traits in cultivated peanut, to permit rapid selection of superior quality genotypes in the breeding program. SSR markers linked to pod and kernel traits were identified in two DNA pools (high and low), which were established using selected F2:6 recombinant individuals resulting from a cultivated cross between a runner (Tamrun OL01) and a Spanish (BSS 56) peanut. To identify quantitative trait loci (QTLs) for pod and kernel-related traits, parents were screened initially with 112 SSR primer pairs. The survey revealed 8.9% polymorphism between parents. Of ten SSR primer pairs distinguishing the parents, five (PM375, PM36, PM45, pPGPseq8D9, and Ah-041) were associated with differences between bulks for seed length, pod length, number of pods per plant, 100-seed weight, maturity, or oil content. Association was confirmed by analysis of segregation among 88 F2:6 individuals in the RIL population. Phenotypic means associated with markers for three traits differed by more than 40%, indicating the presence of QTLs with major effects for number of pods per plant, plant weight, and pod maturity. The SSR markers can be used for marker assisted selection for quality and yield improvement in peanut. To the best of our knowledge, this is the first report on the identification of SSR markers linked to pod - and kernel- related traits in cultivated peanut. <![CDATA[<b>Influence of metal ions and organic carbons on denitrification activity of the halotolerant bacterium, <i>Paracoccus pantotrophus</i> P16 a strain from shrimp pond</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200004&lng=es&nrm=iso&tlng=es The effect of metal ions, ferric ion (Fe3+) and molybdenum ion (Mo6+) on the denitrification process of Paracoccus pantotrophus P16 grown under saline conditions was investigated. Results revealed that the dosages of added Fe3+ and Mo6+ significantly accelerated nitrate utilization and nitrite accumulation. Enzymatic studies revealed that the membrane-bound nitrate reductase and the periplasmic nitrite reductase had activities of 998 ± 28 and 373 ± 18 nmol (mg protein)-1 min-1, respectively after growing Paracoccus pantotrophus P16 in medium supplemented with 1.5 µM Fe3+. If provided with 1.5 µM Fe3+and 2.4 µM Mo6+, the membrane-bound nitrate reductase activity increased to 6,223 ± 502 nmol (mg protein)-1 min-1 and the periplasmic nitrite reductase was 344 ± 20 nmol (mg protein)-1 min-1. The results indicated that an addition of Fe3+ and Mo6+ led to an overstimulation of nitrate reductase activity as compared with nitrite reductase activity. When glucose was supplied, the minimal ratio of carbon per nitrate (C/N) was 2.31 mg C/mg NO3--N with denitrification yield of 0.45 g NO3--N/g C. Addition of ethanol instead of glucose, the minimal ratio of C/N was 1.15 mg C/mg NO3--N with denitrification yield of 1.08 g NO3--N/g C. <![CDATA[<b>Molecular characterization of <i>'Candidatus</i> Liberibacter' species/strains causing huanglongbing disease of citrus in Kenya</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200005&lng=es&nrm=iso&tlng=es This study was undertaken to characterize the alpha subgroup of the proteobacteria causing the huanglongbing (HLB) disease of citrus from three different ecological zones of Kenya namely the Lower highlands (LH2, LH3, 1800-1900 m above sea level); Upper midlands (UM3, UM4, 1390-1475m), Lower midlands (LM5, LM4, LM3 of 1290-1340-1390m), by isolation and sequencing DNA encoding the L10 and L12 ribosomal proteins and the intergenic region. A 7I6-basepair DNA fragment was amplified and sequenced and consisted of 536 basepairs of DNA encoding the L10 protein, 44 basepairs of DNA intergenic region and 136 basepairs of DNA that partially encodes the L12 protein. Sequences of rpL10/L12 protein genes from Kenyan strains were 98% and 81% similar to the South African 'Candidatus Liberibacter africanus strain Nelspruit' and the Asian 'Candidatus Liberibacter asiaticus' strains, respectively. The intergenic rDNA sequence of Kenyan strain from UM and LM showed 84% similarity with 'Candidatus L. africanus strain Nelspruit' and 50% similarity with 'Candidatus L. asiaticus' strain. However, the LH strain had an 11- basepairs deletion, while the LM4 had a 5-basepair deletion in the intergenic region compared to 'Candidatus L. africanus strain Nelspruit'. The L10 amino acid sequence was 100% homologous among HLB bacteria obtained from the agro-ecological zones in Kenya and the L10 protein sequence was also homologus to 'Candidatus L. africanus strain Nelspruit'. Nevertheless, the L10 amino acid sequence of 'Candidatus L. asiaticus' and the 'Candidatus L. africanus subsp. capensis' differed from the Kenyan strains by 18.36% and 11.82%, respectively. Phylogenetic analysis of both the L10/L12 rDNA sequences and the L10 amino acid sequences clustered the Kenyan strains of the 'Candidatus Liberibacter' species with members of alpha subdivision of proteobacteria. <![CDATA[<b>Preservation of endangered Tunisian grapevine cultivars using embryogenic cultures</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200006&lng=es&nrm=iso&tlng=es The preservation of embryogenic lines derived from several endangered local grapevine cultivars was studied. Embryogenic calluses were obtained from immature anthers of eight cultivars, sampled on both fruity-cuttings and field grown vines. Anthers at the 'separated flower' stage, derived from fruity-cuttings, resulted in an increased induction of somatic embryogenesis, compared to those derived from the field. Pro-embryogenic calluses were induced on Chée and Pool (1987) basal medium, supplemented with 9 µM of 2,4-dichlorophenoxyacetic acid (2,4-D) and 11.35 µM of thidiazuron (TDZ) under dark conditions. Different anther zones (filament, abaxial, adaxial, lateral zones and entire anthers) were involved in somatic embryogenesis induction. The percentages of granular and yellowish pro-embryogenic calluses ranged between 15.6% and 34.8% in 'Kahli Kerkennah' and 'Muscat Raf-raf' cultivars, respectively. Although, morphological diversifications of pro-embryogenic calluses (several necrosis and spontaneous maturation) were observed on the induction mediumafter 5 subcultures. The reduction of 2,4-D and TDZ levels to 4.52 µM and 2.89 µM respectively, induced granular and yellowish embryogenic material. Thus, Chée and Pool (1987) (CP) enriched with 4.52 µM of 2,4-D and 2.89 µM of TDZ revealed to be the most appropriate for long-term maintenance. In fact, all the cultivars presented high and regular embryo maturation rates after 12, 24, 36 and 48 months of cultivation on this medium, under light conditions. After 4 years, they still exhibit high germination and regeneration abilities. Germination of somatic embryos was achieved on Murashige and Skoog (1962) basal-medium, with rates ranging from 69% to 96%. Only 5% of somatic embryos were concerned by morphological variations. The regenerated plantlets presented a normal phenotype under controlled greenhouse conditions, compared to mother plants. <![CDATA[<b>Technical and economic feasibility of gradual concentric chambers reactor for sewage treatment in developing countries</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200007&lng=es&nrm=iso&tlng=es A major challenge in developing countries concerning domestic wastewaters is to decrease their treatment costs. In the present study, a new cost-effective reactor called gradual concentric chambers (GCC) was designed and evaluated at lab-scale. The effluent quality of the GCC reactor was compared with that of an upflow anaerobic sludge bed (UASB) reactor. Both reactors showed organic matter removal efficiencies of 90%; however, the elimination of nitrogen was higher in the GCC reactor. The amount of biogas recovered in the GCC and the UASB systems was 50% and 75% of the theoretical amount expected, respectively, and both reactors showed a slightly higher methane production when the feed was supplemented with an additive based on vitamins and minerals. Overall, the economical analysis, the simplicity of design and the performance results revealed that the GCC technology can be of particular interest for sewage treatment in developing countries. <![CDATA[<b>AgNO<sub>3</sub></b>: <b>a potential regulator of ethylene activity and plant growth modulator</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200008&lng=es&nrm=iso&tlng=es The aim of this review is to critically analyze the role of silver nitrate (AgNO3) in modulating plant growth and development. In recent years, basic studies on ethylene regulation opened new vistas for applied research in the area of micro-propagation, somatic embryogenesis, in vitro flowering, growth promotion, fruit ripening, and sex expression. Silver nitrate has proved to be a very potent inhibitor of ethylene action and is widely used in plant tissue culture. Few properties of silver nitrate such as easy availability, solubility in water, specificity and stability make it very useful for various applications in exploiting plant growth regulation and morphogenesis in vivo and in vitro. Silver ion mediated responses seem to be involved in polyamines, ethylene- and calcium- mediated pathways, and play a crucial role in regulating physiological process including morphogenesis. The molecular basis for regulation of morphogenesis under the influence of silver nitrate is completely lacking. This review compiles published reports of silver nitrate-mediated in vitro and in vivo studies and focuses on fundamental and applied aspects of plant growth modulation under the influence of silver nitrate. <![CDATA[<b>A rapid and cheap protocol for preparation of PCR templates in peanut</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200009&lng=es&nrm=iso&tlng=es This paper describes a simple, low cost and reliable DNA template preparation protocol for polymerase chain reaction (PCR) using immature leaves from peanut seeds or leaves from field-grown plants. The technique may find wide utility in studies involving PCR-based molecular markers, rapid screening for transformants and gene cloning. <![CDATA[<b>Genetic and physical map of broad host range cosmid pRG930cm</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200010&lng=es&nrm=iso&tlng=es We hereby present the complete sequence and annotation of pRG930cm, a spectinomycin/streptomycin/chloramphenicol-resistant cosmid vector. pRG930cm (17,256 bp; GenBank Accession No.: FM174471) has a broad host range, and is stably maintained by a number of Gram-negative bacteria including Pseudomonas spp, Escherichia coli, Agrobacterium tumefaciens and Azorhizobium caulinodans ORS571. pRG930cm is already widely used and its sequence will aid efficient construction and analysis of cosmid libraries. <![CDATA[<b>Isolation of high quality DNA</b>: <b>a protocol combining “rennet” and glass milk</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200011&lng=es&nrm=iso&tlng=es High quality DNA is essential for many molecular biology techniques. However, the reagents used for that purpose usually are expensive and/or cause a high environmental impact. Here, we describe two alternative protocols that use inexpensive reagents and are not hazardous to the environment. The first protocol utilizes the enzyme chymosin, normally used as “rennet” in cheese production and which is easily obtained on the commercial market. The second protocol uses “rennet DNA extraction protocol” combined with the DNA binding capacity of glass powder (glass milk), which can easily be “home made”. The first protocol is used when a high yield of DNA is needed, whereas the second protocol is used for production of a higher quality DNA, being able to work with sparse samples. <![CDATA[<b>Measuring </b><b>b</b><b>-Galactosidase activity at pH 6 with a differential pH sensor</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200012&lng=es&nrm=iso&tlng=es The b-Galactosidase activity at pH 6 is used as a cellular marker to identify senescent cell cultures. The classic method to identify this enzymatic activity is using cytochemical staining with X-Gal after 16 hrs. In this work, a differential pH sensor was used to measure b-Galactosidase activity at pH 6. The measurement is easy and only takes 3 min. <![CDATA[<b>Novel antiviral activity of dialdehyde starch</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582009000200013&lng=es&nrm=iso&tlng=es A significant effort worldwide is being directed toward development of novel biocides against drug-resistant bacterial and viruses because of the significant potential human infection risks in the general population. We report here the discovery of a strong antiviral biocide, dialdheyde starch (DAS). Antiviral tests were carried out against three non-envelop viruses, including two bacterial viruses MS2 and PRD1, and one human virus Poliovirus. Dialdehyde starch aqueous suspensions were effective biocides against these three test viruses in a 1 hr exposure test. The antiviral activity was significantly enhanced in a four-hour exposure test, with maximum seven orders of magnitude reductions against MS2 and PRD1, and four-order reduction against Poliovirus. The antiviral activity of dialdehyde starch was found to be pH dependent, being more active in alkaline and acidic conditions than in neutral conditions.