Scielo RSS <![CDATA[Electronic Journal of Biotechnology]]> http://www.scielo.cl/rss.php?pid=0717-345820110002&lang=es vol. 14 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<strong>Accommodating the difference in students' prior knowledge of cell growth kinetics</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200001&lng=es&nrm=iso&tlng=es This paper describes the development and benefits of an adaptive digital module on cell growth to tackle the problem of educating a heterogeneous group of students at the beginning of an undergraduate course on process engineering. Aim of the digital module is to provide students with the minimal level of knowledge on cell growth kinetics they need to comprehend the content knowledge of the subsequent lectures and pass the exam. The module was organised to offer the subject matter in a differentiated manner, so that students could follow different learning paths. Two student groups were investigated, one consisting of students who had received their prior education abroad and one of students that had not. Exam scores, questionnaires, and logged user data of the two student groups were analysed to discover whether the digital module had the intended effect. The results indicate that students did indeed follow different learning paths. Also, the differences in exam scores between the two student groups that was present before the introduction of the digital module was found to have decreased afterwards. In general, students appreciated the use of the material regardless of their prior education. We therefore conclude that the use of adaptive digital learning material is a possible way to solve the problem of differences in prior education of students entering a course. <![CDATA[<b>Biochemical properties of an extracellular </b><b><b>β-D</b>-fructofuranosidase II produced by <i>Aspergillus phoenicis</i> under Solid-Sate Fermentation using soy bran as substrate</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200002&lng=es&nrm=iso&tlng=es The filamentous fungus A. phoenicis produced high levels of ?-D-fructofuranosidase (FFase) when grown for 72 hrs under Solid-State Fermentation (SSF), using soy bran moistened with tap water (1:0.5 w/v) as substrate/carbon source. Two isoforms (I and II) were obtained, and FFase II was purified 18-fold to apparent homogeneity with 14% recovery. The native molecular mass of the glycoprotein (12% of carbohydrate content) was 158.5 kDa with two subunits of 85 kDa estimated by SDS-PAGE. Optima of temperature and pH were 55�C and 4.5. The enzyme was stable for more than 1 hr at 50�C and was also stable in a pH range from 7.0 to 8.0. FFase II retained 80% of activity after storage at 4�C by 200 hrs. Dichroism analysis showed the presence of random and ?-sheet structure. A. phoenicis FFase II was activated by Mn2+, Mg2+ and Co2+, and inhibited by Cu2+, Hg2+ and EDTA. The enzyme hydrolyzed sucrose, inulin and raffinose. Kd and Vmax values were 18 mM and 189 U/mg protein using sucrose as substrate. <![CDATA[<strong>Biosorption kinetics of a direct azo dye Sirius Blue K-CFN by <i>Trametes versicolor</i></strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200003&lng=es&nrm=iso&tlng=es In this study, lyophilized Trametes versicolor biomass is used as a sorbent for biosorption of a textile dye, Sirius Blue K-CFN, from an aqueous solution. The batch sorption was studied with respect to dye concentration, adsorbent dose and equilibrium time. The effect of pH and temperature on dye uptake was also investigated and kinetic parameters were determined. Optimal initial pH (3.0), equilibrium time (2 hrs), initial dye concentration ( 100 mg l-1) and biomass concentration (1.2 mg l-1) were determined at 26�C. The maximum biosorption capacity (q max) of Sirius Blue K-CFN dye on lyophilized T. versicolor biomass is 62.62 mg/g. The kinetic and isotherm studies indicated that the biosorption process obeys to a pseudo-second order model and Langmuir isotherm model. In addition, the biosorption capacities of fungal biomass compared to other well known adsorbents such as activated carbon and Amberlite, fungal biomass biosorptions capacities were found to be more efficient. <![CDATA[<strong>Characterization of novel genic SSR markers in <i>Linum usitatissimum</i> (L.) and their transferability across eleven <i>Linum</i> species</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200004&lng=es&nrm=iso&tlng=es Little is known about the evolutionary relationships among Linum species, basically because of the lack of transferable molecular markers. Currently, expressed sequence tags available in public databases provide an opportunity for the rapid and inexpensive development of simple sequence repeat (SSR) markers in wild flax species. In this regard, fifty expressed sequence tag-derived microsatellite markers (EST-SSRs) were evaluated for polymorphism and transferability in 50 Linum usitatissimum cultivars/accessions and 11 Linum species. Among them 23 EST-SSRs were polymorphic in L. usitatissimum, while 2-4 alleles were detected (average 2.26 per locus). The polymorphism information content value ranged from 0.08 to 0.55 (average 0.38). Forty one genic markers (95.3%) produced strong amplicons in at least two of the 11 Linum species. The percentage of cross amplification ranged from 34.1% to 92.7% in L. tauricum and L. bienne, respectively. Moreover, the rate of transferability was associated positively with the botanical section. Our results suggest that the high degree of EST-SSRs transferability to Linum species can be a useful enhancement of the current database of SSR markers for future genetic and evolutionary studies. <![CDATA[<b>Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200005&lng=es&nrm=iso&tlng=es Production of good quality beer is dependent largely on the fermentation temperature and yeast strains employed during the brewing process, among others. In this study, effects of fermentation temperatures and yeast strain type on beer quality and spent yeast density produced after wort fermentation by two commercial yeast strains were investigated. Beer samples were assessed for colour, clarity and foam head stability using standard methods, whilst the compositions and concentration of Beer Volatile Compounds (BVCs) produced were assessed using GC-MS. The spent yeast density, measured as dry cell weight, ranged between 1.84 - 3.157 mg/ml for both yeast strains with the highest yield obtained at room temperature fermentation. A peak viable population of 2.56 x 10(7) cfu/ml was obtained for strain A, also during fermentation at room temperature. The foam head of the beers produced at 22.5�C was most stable, with foam head ratings of 2.66 and 2.50 for yeast strain A and B, respectively. However, there was no significant (p = 0.242) difference in colour intensity between the beers produced at the different fermentation temperatures. Eight different BVCs were detected in all beer samples and were found to affect the organoleptic properties of the beer produced. Further optimizations are required to determine the effects of other parameters on beer quality. <![CDATA[<strong>High density process to cultivate <i>Lactobacillus plantarum</i> biomass using wheat stillage and sugar beet molasses</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200006&lng=es&nrm=iso&tlng=es Background: Owing to the growing interest in biofuels, the concept of a biorefinery where biomass is converted to a variety of useful products is gaining ground. We here present how distillery waste is combined with a by-product from a sugar production, molasses, to form a medium for the growth of Lactobacillus plantarum with yields and biomass densities comparable with conventional industrial media. Such approach enables a cost-effective utilization of the problematic wastewater from ethanol and a by-product from sugar production. It is the first approach that attempts to find low-cost media for the production of Lactobacillus plantarum biomass. Results: This study suggests that sieved wheat stillage enriched by adding 1.77 g/l yeast extract and 10% molasses (v/v), with NH4OH used for pH adjustment, may be used as a media for large-scale cultivation of L. plantarum. Such composition of the medium permits a high density of lactic acid bacteria (1.6 x 10(10) cfu/ml) to be achieved. Conclusions: The use of a fermentation medium consisting of distillery wastewater and molasses to obtain value-added products (such as LAB biomass and lactic acid) is a possible step for classical ethanol production to move towards a biorefinery model production in which all by and waste products are utilized to increase produced values and reduce waste production. This enables a cost-effective utilization of the problematic wastewater from ethanol and sugar production. <![CDATA[<strong>New stereoisomeric derivatives of jasmonic acid generated by biotransformation with the fungus <i>Gibberella fujikuroi</i> affect the viability of human cancer cells</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200007&lng=es&nrm=iso&tlng=es Background: Several studies have shown that (-)-Jasmonic acid, (+)-7-iso-Jasmonic acid and its methyl ester, methyl jasmonate, have anti-cancer activity in vitro and in vivo, exhibiting selective cytotoxicity towards cancer cells. The degree of activity of these molecules is strongly related to their stereochemistry. The biotransformation of known compounds, natural or synthesized, related to interesting biological activities, generates new molecules displaying new improved properties compared with the original ones, increasing its value and providing new more effective products. Therefore, based on the above rationales and observations, in this work a biotransformation protocol to modify the chemical structure of the plant hormone jasmonic acid by using the fungus Gibberella fujikuroi was established. Results: The three jasmonic acid derivatives obtained, 3(S)-Hydroxy-2(R)-(2Z-pentenyl)-cyclopentane-1(R)-acetic acid (1), 3(R)-Hydroxy-2(R)-(2Z-pentenyl)-cyclopentane-1(R)-acetic acid (2), 3-Hydroxy-2(S)-(2Z-pentenyl)-cyclopentane-1(S)-acetic acid (3), were tested for cell-growth inhibition activity towards the human cancer epithelial cell line, the oral squamous carcinoma cells (KB). The results obtained show that jasmonic acid derivatives (1-3) are active on human cancer cells examined in different concentration ranges, with IC50 value less than of 25 �M. The compound 3, with the same molecular structure of compounds 1 and 2, but with different stereochemistry, was more active confirming that the activity of jasmonate compounds is related to their stereochemistry and to substituents in the cyclopentane ring. In this study, we also tested the potential proapoptotic activity of compound 3, and our data suggest that it, as other jasmonate compounds, is able to trigger apoptotic death in cancer cells. This event may be correlated at an elevation of reactive oxygen species (ROS). Administration of N-acetylcysteine (NAC) prevented compound 3 cytotoxicity. Conclusions: This work shows for the by first time the production of hydroxylated derivatives of JA by biotransformation. The activity observed of these compounds in cancer cells is higher than the observed with JA and is strongly related to its stereochemistry. <![CDATA[<strong>Rapid automated selection of mammalian cell line secreting high level of humanized monoclonal antibody using Clone Pix FL system and the correlation between exterior median intensity and antibody productivity</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200008&lng=es&nrm=iso&tlng=es The selection of high-producing mammalian cell lines is a crucial step in process development for the production of biopharmaceuticals. Previously, cloning by limiting dilution method was used to isolate monoclonal NS0 cells secreting high levels of humanized-C2 monoclonal antibodies. However limiting dilution method is time consuming, has low probability of monoclonality and is significantly limited by the number of clones that can be feasibly screened. In order to minimize the duration and to increase the probability of obtaining high-producing clones with high monoclonality, an automated colony picker, Clone Pix FL system was used to replace limiting dilution method. We were able to screen 1 x 10(5) clones secreting humanized monoclonal antibodies and high producer clones were selected in just 7 days. Briefly, semi-solid media was used to immobilize single cells separately and allow them to proliferate into discrete clones. The high viscosity nature of the semi-solid media retains the secreted products in the vicinity of the associated clones. Using Clone Pix FL system, all clones were screened and the producer clones with different exterior fluorescent intensities were automatically isolated. We were able to isolate rare high-producers (> 3000 FU) with frequency of as low as 0.003% of the population. A quantitative ELISA was also performed to evaluate the correlation between the fluorescence intensity of clones with its corresponding antibody productivity. Clones with fluorescence intensity of < 1000 FU showed relatively low antibody productivity compared with those greater than 1000 FU; however above this there was no correlation of production with the increase in fluorescence intensity. Hence, although the high-throughput, rapid and automated nature of Clone Pix FL system allows the screening of large number of cells in a short period of time with also an increased in the probability of obtaining rare and precious high-producing clones, downstream analysis are still vital to determine the ?actual? and stable high producer clones. <![CDATA[<b>Xylanolytic enzymes production by <i>Aspergillus niger </i>GS1 from solid-state fermentation on corn stover and their effect on ruminal digestibility</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200009&lng=es&nrm=iso&tlng=es Hemicellulosic agricultural by-products such as corn stover (CS) are highly available materials which represent an opportunity to develop value added products. Native Aspergillus niger GS1 was used for solid-state fermentation (SSF) on alkali pre-treated CS (ACS) aimed to optimize xylanolytic enzymes production, and their effect on in vitro ruminal and true digestibility of ACS. Enzyme production was empirically modelled using a fractional factorial design 2(9-5), and the resulting significant factors were glucose, yeast extract and two mineral salts, which were arranged in a Draper-Lin optimization design at two levels. Predicted optimum xylanolytic activity of 33.6 U (mg protein)-1 was achieved at 48 hrs of SSF, and was validated by confirmatory experiments. ACS was incubated with a semipurified enzymatic extract (EE) showing a xylanolytic activity of 1600 U kg-1 dry ACS for 12 hrs before exposure to cow?s ruminal liquid for 72 hrs, which led to 5% and 10% increase of in vitro ruminal and true digestibility, respectively. CS is a readily available by-product in different regions which after alkaline treatment and partial hydrolysis with the EE, may be advantageously used as supplement for ruminant feed. <![CDATA[<strong>Sodium azide mutagenesis resulted in a peanut plant with elevated oleate content</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200010&lng=es&nrm=iso&tlng=es Screening of peanut seeds resulting from 0.39% sodium azide treatment with NIRS calibration equation for bulk seed samples identified a plant with more than 60% oleate. Oleate content in individual seeds of the plant, as predicted by NIRS calibration equation for intact single peanut seeds, ranged from 50.05% ~ 68.69%. Three seeds with >60% oleate thus identified were further confirmed by gas chromatography. Multiple sequence alignments of the FAD2B gene from Huayu 22 (wild type) and peanut seeds with elevated oleate (mutant type) revealed a C281T transition in the coding region causing an I94T substitution in the oleoyl-PC desaturase, which may be responsible for reduction in the enzyme activity. <![CDATA[<strong>Construction and application of a built-in dual luciferase reporter for microRNA functional analysis</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582011000200011&lng=es&nrm=iso&tlng=es Background: As key gene regulators, microRNAs post-transcriptionally modulate gene expression via binding to partially complementary sequence in the 3? UTR of target mRNA. An accurate, rapid and quantitative tool for sensing and validation of miRNA targets is of crucial significance to decipher the functional implications of miRNAs in cellular pathways. Results: Taking advantage of an improved restriction-free cloning method, we engineered a novel built-in dual luciferase reporter plasmid where Firefly and Renilla luciferase genes were assembled in a single plasmid named ?pFila?. This design eliminates the transfection of a separate control plasmid and thus minimizes the time and labor required for miRNA-target sensing assays. pFila consistently produces Firefly and Renilla luciferase activities when transfected into human-, monkey- and mouse-derived mammalian cell systems. Moreover, pFila is capable of recapitulating the interaction of miR-16 and its known target CCNE1 in Hela cells. Additionally, pFila is shown to be a sensitive miR-biosensor by evaluating the inhibition efficiency of endogenous miRNA. Conclusions: pFila would facilitate miRNA target identification and verification in a rapid and simplified manner. Also, pFila is a sensitive biosensor for active miRNA profiling in vivo.