Browsing by Autor "Virginia A. Vargas"

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A comparative evaluation of microalgae for the degradation of piggery wastewater under photosynthetic oxygenation
(Elsevier BV, 2010) Ignacio de Godos; Virginia A. Vargas; Saúl Blanco; María Cruz García-González; Roberto Soto; Pedro A. García‐Encina; Eloy Bécares; Raúl Muñoz
Assessing carbon and nitrogen removal in a novel anoxic–aerobic cyanobacterial–bacterial photobioreactor configuration with enhanced biomass sedimentation
(Elsevier BV, 2014) Ignacio de Godos; Virginia A. Vargas; Héctor Guzmán; Roberto Soto; Blanca García Gómez; Pedro A. García‐Encina; Raúl Muñoz
Bacillus bogoriensis sp. nov., a novel alkaliphilic, halotolerant bacterium isolated from a Kenyan soda lake
(Microbiology Society, 2005) Virginia A. Vargas; Osvaldo D. Delgado; Rajni Hatti‐Kaul; Bo Mattìasson
Strain LBB3(T) isolated from Bogoria soda lake in Kenya is an alkaliphilic, Gram-positive, strictly aerobic, non-motile, spore-forming bacterium. It was identified as a member of the genus Bacillus on the basis of phenotypic and phylogenetic analyses. The organism grows optimally at 37 degrees C and pH 10. The G+C content of the genomic DNA is 37.5 mol%. 16S rRNA gene sequence analysis showed 95 and 96 % sequence similarity with Bacillus pseudofirmus (DSM 8715(T)) and Bacillus alcalophilus (DSM 485(T)), respectively. Furthermore, DNA-DNA hybridization against these two Bacillus species showed 39.0 and 55.5 % similarity, respectively. Based on our observations, strain LBB3(T) is proposed to represent a novel species of the genus Bacillus, for which the name Bacillus bogoriensis sp. nov. is proposed. The type strain of B. bogoriensis is LBB3(T) (=ATCC BAA-922(T)=LMG 22234(T)).
BIOSORPTION OF LEAD(II) IONS BY DEAD BACTERIAL BIOMASS ISOLATED FROM MINE WATER
(2021) Alejandro Canaza; Lizzette Pozo; Erick Ferrufino-Guardia; Virginia A. Vargas; Erick Ferrufino-Guardia; Centro de Biotecnología, Facultad de Ciencias y Tecnología, Universidad Mayor de San Simón, Campus Universitario s/n, Cochabamba, Cochabamba-Bolivia.; Virginia A. Vargas; Centro de Biotecnología, Facultad de Ciencias y Tecnología, Universidad Mayor de San Simón, Campus Universitario s/n, Cochabamba, Cochabamba-Bolivia.
El plomo y sus diferentes formas químicas se han utilizado ampliamente en la industria durante los últimos años y el resultado es la alta contaminación detectada en el agua y el suelo. Se aislaron microorganismos resistentes al plomo (II) de muestras líquidas recolectadas en Mina Asientos, Cochabamba-Bolivia. Se aislaron once cepas en medio sólido con 200 ppm de Pb (II) y se seleccionaron 4 cepas para remoción de metales en muestras líquidas, una cepa presentó los valores de remoción de Pb (II) más altos para 250 ppm de Pb (II). La cepa seleccionada designada como MA-4 se sometió a estudios filogenéticos y mostró una similitud de secuencia del 99,9% con Pseudomonas monteilii. La biosorción sigue los modelos de isotermas de Langmuir y Freundlich, con valores de qmax y Kf de 166,67 y 11,09, respectivamente. Estos resultados implicaron una fuerte capacidad de unión a la biomasa muerta y su potencial aplicación en el proceso de biosorción.
CELLULASE PRODUCTION BY MICROORGANISMS ISOLATED FROM LAGUNA BLANCA, POTOSÍ-BOLIVIA
(2021) Verushka Camacho; Roberto Soto; Héctor Guzmán; Virginia A. Vargas; Héctor Guzmán; Centro de Biotecnología, Universidad Mayor de San Simón, Cochabamba, Bolivia.; Virginia A. Vargas; Centro de Biotecnología, Universidad Mayor de San Simón, Cochabamba, Bolivia.
Las cepas bacterianas aisladas de muestras de agua recolectadas de Laguna Blanca, Potosí-Bolivia, y depositadas en el Centro de Biotecnología, Cochabamba-Bolivia, fueron sometidas a estudios de producción de celulasas. Entre 71 cepas, 32 se seleccionaron como positivas en medio líquido utilizando papel de filtro como única fuente de carbono. Nueve cepas reportaron mayor actividad de celulasas y se evaluó el efecto de la concentración de NaCl y el pH sobre el crecimiento de microorganismos. Siete cepas se identificaron como halófilas mientras que 2 fueron halotolerantes. Según el valor de pH del medio de cultivo, 5 cepas fueron neutrófilas y 4 alcalotolerantes. Las cepas codificadas como LB-4 y LB-8 fueron seleccionadas como mejores productoras de celulasas. Además, la producción de celulasas utilizando productos forestales y residuos agroindustriales fue positiva para diferentes tipos de papel y madera de pino, sin embargo, se detectaron valores de actividad más altos con cáscara de plátano y bagazo de caña de azúcar. Se seleccionó la cepa LB-8 como la mejor productora de celulasas bajo las condiciones utilizadas en este estudio con una actividad enzimática de 2.774 U/ml. Los análisis filogenéticos mostraron una similitud de secuencia del 99,99 % entre la cepa LB-8 y Bacillus pumilus.
Coagulation/flocculation-based removal of algal–bacterial biomass from piggery wastewater treatment
(Elsevier BV, 2010) Ignacio de Godos; Héctor Guzmán; Roberto Soto; Pedro A. García‐Encina; Eloy Bécares; Raúl Muñoz; Virginia A. Vargas
Functional stratification and enzymatic arrangement in microbial communities across a hypersaline depth gradient
(Frontiers Media, 2025) C. Hoepfner; Daniel Guzmán; Boris Vidal‐Veuthey; V. Foronda; Antonia Beggs; Juan Pablo Cárdenas; Virginia A. Vargas; Fernando D. Alfaro
Extreme environments comprise a significant portion of Earth's terrestrial surface, posing challenges, such as extreme temperatures, pressure, pH extremes, oxygen and nutrient scarcity, and high salinity. Hypersaline ecosystems, such as those in the Andean Cold Deserts, exemplify extreme environments where microbial life has evolved specialized survival mechanisms. The Central Andean Mountains host extensive salt flats exposed to extreme temperature fluctuations, intense ultraviolet radiation, and high soil salinity. While most studies focus on surface layers, the impact of soil depth on functional diversity remains poorly understood. This study utilized shotgun metagenomics and functional annotation to explore enzymatic diversity across a 8-meter depth gradient in the Uyuni Salt Flat aiming to understand microbial adaptations to depth and abiotic stress. Our findings revealed a complex, stratified microbial ecosystem. Surface layers showed high abundance of amylases, enzymes that degrade accessible carbohydrates, likely derived from photosynthetic communities or surface-imported organic matter. These patterns suggest a dominance of strategies for rapid carbon decomposition. Intermediate depths exhibited elevated lipase and peroxidase activity, reflecting the presence of complex lipids and oxidative stress management, essential for survival in oxygen-limited, high-salinity zones. Lipase support lipid utilization as a carbon source, while peroxidase activity points to redox adaptations for microbial resilience under fluctuating oxidative conditions. Deeper sediment layers showed a shift toward protease and peptidase activity, indicating organic nitrogen recycling in nutrient-deprived environments and suggesting an efficient protein degradation system among halophilic archaea. Peroxidases remained abundant even at these depths, supporting sustained redox regulation and biogeochemical cycling thus enabling microbes to manage redox imbalances in high-salinity, low-oxygen settings. The enzymatic diversity across the depth gradient demonstrates functional stratification and remarkable microbial adaptability to hypersaline conditions. This functional resilience underpins nutrient cycling and organic matter decomposition deep in the salt flats. Notably, the identified halophilic enzymes, stable and active under high-salinity conditions, hold significant potential for biotechnological applications. This study contributes to our understanding of microbial life's complexity in hypersaline environments, enhancing our ability to harness extremophilic enzymes for biotechnological applications while underscoring the ecological value of these unique habitats.
Leaching of aluminium from post-consumer beverage packaging residual PolyAl using biogenic organic acids: Towards low-cost, sustainable recycling
(Elsevier BV, 2025) Jhonny Pinaya; Yuliia Boiko; Mohamed A. Ismail; Jan E. Wahlberg; Sang‐Hyun Pyo; Virginia A. Vargas; Rajni Hatti‐Kaul
Plastic packaging provides enormous benefits for preservation and transportation of food and beverage products. However, recycling the multilayered packaging materials represents a challenge due to the complexity of separating the components making up the different layers. The drinks packaging, having aluminium (Al) as a light barrier placed between polyethylene layers inside the paperboard carton, comprises a significant category of post-consumer waste in need of complete recycling. Microbially produced organic acids are gaining attention for recovery of metals from industrial residues. This report presents a study on evaluation of acetic- and gluconic acid, which are known to be produced by acetic acid bacteria, for leaching out the Al from Tetra Pak PolyAl material remaining after removal of the paperboard. By using Taguchi design technique L9 (3)4, optimal conditions for 100 % Al leaching from 1 % (w/v) PolyAl (0.4 cm2) were determined to be treatment at pH 1 and 50 °C with 0.25 M acetic acid for 6 days or 1 M gluconic acid for 15 days. Increasing the PolyAl concentration to 2 % w/v and particle size to 4 cm2 resulted in increase in the time for maximal Al leaching. Various microscopic, spectroscopic and thermal analyses techniques confirmed the removal of Al and revealed no notable change in the properties of the residual PE. The metal released was recovered nearly quantitatively (99.5 %) by precipitation as Al(OH)3 only from the acetic acid leachate. The results indicate the potential of the leaching method in providing a greener route for recycling the Al containing packaging material using biogenic organic acids.
LIPOLYTIC ENZYME PRODUCTION BY HALOPHILIC/HALOTOLERANT MICROORGANISMS ISOLATED FROM LAGUNA VERDE, BOLIVIA
(2008) Mariana Niño de Guzmán; Virginia A. Vargas; Henry Antezana; Michal Svoboda
Bacterial strains isolated from water samples from Laguna Verde, Potosi-Bolivia and deposited at Biotechnology Center, Cochabamba-Bolivia, were subjected to lipolytic enzyme production studies. Among these, 10 strains were selected as positive in lipolytic enzyme production in solid medium, using olive oil as sole carbon source. Selected strains were subjected to morphological and biochemical studies. Enzyme production in liquid medium identified strain LV01 as the best enzyme producer with 0.079 U/ml lipolytic activity. Partial purification by ion-exchange chromatography of the lipolytic enzyme, produced by strain LV01, presented specific enzyme activity of 0,138 U/mg of eluted protein with approximately 77 KDa size. Partial characterization of the produced enzyme revealed its display maximum activity values at pH 9, 30°C y 1.7M NaCl , thus exhibiting remarkably haloalkalitolerant properties. The 16S rDNA gene sequence analysis showed 99% similarity between strain LV01 and Bacillus pumilus (embAJ494727).
New diatom taxa from high-altitude Andean saline lakes
(Taylor & Francis, 2012) Saúl Blanco; Irene Álvarez‐Blanco; Cristina Cejudo‐Figueiras; Ignacio de Godos; Eloy Bécares; Raúl Muñoz; Héctor Guzmán; Virginia A. Vargas; Roberto Soto
Abstract During a biological survey carried out in five shallow, high-altitude saline lakes of the Bolivian Altiplano in 2009, six unknown diatom taxa were found in various lake populations. Detailed light and scanning electron microscopy observations allowed the description of the following new taxa: Navicula venetoides (distinguished from N. veneta Kützing by having coarser lineate striae), Pinnularia boliviana (similar to P. rhombarea var. halophila Krammer but with coarser striae and a narrower central area), Nitzschia sansimoni (morphologically close to N. supralitorea Lange-Bertalot, the latter having denser striae), Surirella striatula var. halophila (differing from the nominate and other varieties in a distinctly heteropolar outline and the presence of denser fibulae) and S. moralesii (with large, strictly isopolar valves and a deep pervalvar depression). Differential diagnostic criteria with respect to similar taxa, together with ecological and biogeographical implications of these findings, are briefly discussed. Keywords: AltiplanoBoliviaAndestaxonomyBacillariophyta Acknowledgements Authors are grateful to L. Ector, E.A. Morales and C.E. Wetzel who helped us to collect the bibliographic references, F. Rimet and two anonymous referees for reviewing the manuscript, and A. Sánchez for SEM assistance. The Spanish International Cooperation Agency (A/023287/09) is also gratefully acknowledged.
Production of a lipolytic enzyme originating from Bacillus halodurans LBB2 in the methylotrophic yeast Pichia pastoris
(Springer Science+Business Media, 2005) Santosh Ramchuran; Virginia A. Vargas; Rajni Hatti‐Kaul; Eva Nordberg Karlsson
Protease Production by Bacteria Isolated from Laguna Chiar Khota, Potosi-Bolivia, for Protein Hydrolysates Production
(Springer Science+Business Media, 2022) Jerry L. Solis; Paola Ayala‐Borda; Willy Alvarez; Roberto Soto; Virginia A. Vargas
XYLANASE PRODUCTION USING BARLEY STRAW BY BACILLUS SP. LB-4 ISOLATED FROM LAGUNA BLANCA, POTOSI-BOLIVIA
(Universidad Autónoma del Estado de México, 2012) Cecilia Gandarillas; Roberto Soto; Virginia A. Vargas
"Bacterial strains isolated from water samples collected from Laguna Blanca, Potosi-Bolivia and deposited at Biotechnology Center, Cochabamba-Bolivia, were subjected to xylanolytic enzyme production studies. Among these, 20 strains were selected as positive in xylanolytic enzyme production in liquid medium, using barley straw as sole carbon source and subjected to morphological and biochemical studies. Enzyme production in liquid medium identified strain LB-4 as the best enzyme producer with 10 U/ml xylanolytic activity. Partial characterization of the produced enzyme revealed its display maximum activity values at pH 9, 50°C y 0% (w/v) NaCl concentration, thus exhibiting thermo-alkalitolerant properties. The 16S rDNA gene sequence analysis showed 99% similarity between strain LB-4 and Bacillus pumilus (embAJ494727)."