Browsing by Autor "Cristhian Carrasco"

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A Comprehensive Analysis of the Nutritional Value, Antioxidant Potential and Fatty Acid Composition of Lucuma (Pouteria lucuma) Fruit, Grown in the High-Altitude Valleys of Bolivia.
(National Institutes of Health, 2025) Solan Glez; Cristhian Carrasco; Olof Böök; Grover Castañeta; Erick Loayza; J. Mauricio Peñarrieta; Teodora Popova; Franco M Cabrerizo; Leslie Tejeda
The lucuma tree (Pouteria lucuma), native to South America, is gaining attention for its unique nutritional profile and potential health benefits. This study aimed to analyze the nutritional composition, antioxidant capacity, and fatty acid profile of lucuma fruit from a high-altitude valley in Bolivia. The proximate analysis revealed high levels of carbohydrates (41.7%), dietary fibre (2.4%), and protein (6.9%). Antioxidant assays identified significant amounts of polyphenols, flavonoids, and carotenoids, known for their antioxidant and anti-inflammatory properties. The fruit's fatty acid profile showed a healthy omega-6:omega-3 ratio of 0.21. These results highlight lucuma's potential as a functional food and support further research into its health benefits.
Arabinosylated phenolics obtained from SO2‐steam‐pretreated sugarcane bagasse
(Wiley, 2012) Cristhian Carrasco; Carlos Solano; J. Mauricio Peñarrieta; Henrique Macedo Baudel; Mats Galbe; Gunnar Lidén
Abstract A pentose‐rich hydrolysate fraction obtained by extraction of steam‐pretreated sugarcane bagasse was analysed with regard to dissolved phenolics. The liquid obtained after steam pretreatment (2% SO 2 (w/w) at 190 °C for 5 min) was divided into two parts: one containing dissolved compounds originating from hemicellulose (with xylose as the dominating compound), and the other containing predominantly dissolved compounds originating from lignin. Using nuclear magnetic resonance, the main dissolved compounds originating from lignin were identified as the glycosylated aromatics, 5‐ O ‐( trans ‐feruloyl)‐L‐Arabinofuranose and 5‐ O ‐( trans ‐coumaroyl)‐L‐Arabinofuranose, together with p ‐coumaric acid and small amounts of more common free phenolics such as p ‐hydroxybenzaldehyde, p ‐hydroxybenzoic acid and vanillin. The phenolic compounds were analysed and quantified using reversed‐phase high‐performance liquid chromatography. The findings show that SO 2 steam explosion opened up new degradation pathways during lignin degradation. Copyright © 2012 Society of Chemical Industry
Assessing Pollution Mitigation in Transboundary Waters Through Biosorption Technique in Rural Andean Bolivia
(2026) Alejandra Paz Rios; Paula Cecilia Soto-Rios; Cristhian Carrasco; B. Acevedo-Juárez; Laura Mamani-Garcia; Nidhi Nagabhatla
Heavy metal pollution from mining activities and urban runoff poses a serious threat to public health and aquatic ecosystems in vulnerable communities around the Bolivia–Peru transboundary Lake Titicaca basin. This study evaluates the use of two abundant wetland plants—totora (Schoenoplectus californicus) and reed (Phragmites australis)—as low-cost, locally available biosorbents for the removal of dissolved iron (Fe2+) from the Pallina River, a major contaminant source to Cohana Bay. Monitoring data from Bolivia’s Ministry of Environment and Water (2019–2022) revealed Fe2+ concentrations exceeding the national legal limit (0.3 mg/L) by more than 20 times during the dry season. Laboratory experiments using synthetic Fe2+ solutions (20 mg/L) optimized biosorption conditions, identifying pH 5, 4–6 g/L biomass, fine particle size (0.15–0.212 mm), and a 3 h contact time as optimal. Both plants followed pseudo-second-order kinetics and Langmuir isotherms. Totora showed superior performance, achieving a maximum capacity of 7.8 mg/g compared to reed’s 2.9 mg/g. Continuous-flow column tests removed up to 95% of Fe2+ from synthetic water. When applied to real Pallina River water, totora achieved 50% Fe2+ removal despite reduced efficiency due to competing organic matter. The findings demonstrate the potential of totora-based biosorption as a scalable, nature-based solution for transboundary water management. The policy implications of this study are profound under the national and global water and wetland governance mechanisms and transboundary frameworks like the Binational Autonomous Authority of Lake Titicaca (ALT, est. 1996) and Ramsar Convention.
Brewery spent yeast medium for Serratia sp. bio-beads improves Chenopodium quinoa Willd. growth in the Northern Altiplano of Bolivia
(Oxford University Press, 2025) Ximena Ramirez; V. S. Gonzales; Rogelio Maydana; Mukesh Dubey; Dan Funck Jensen; Cristhian Carrasco; Magnus Karlsson; Carla Crespo
Quinoa (Chenopodium quinoa Willd.) is a climate-resilient Andean crop with high nutritional value and strategic importance for food security in high-altitude regions. However, its productivity in low-input farming systems remains limited. This study developed scalable strategies for propagation and formulation of a Serratia sp. strain as a biofertilizer, using brewery spent yeast (BSY) as growth substrate. Microwave-assisted extraction (MAE) at 1200 W for 15 min significantly (P ≤ 0.05) enhanced soluble protein release from BSY, and MAE-treated media with a C:N ratio of 24:1 supported optimal bacterial growth. Carrageenan-based bio-bead formulations produced at 40°C with 96 g L⁻¹ carrageenan yielded the highest bacterial viability and moisture retention. In a field trial in the Bolivian Altiplano, bio-beads containing Serratia sp. applied at branching stage increased quinoa yield by up to 3.4-fold (P ≤ 0.01) compared with the control. The formulation control also substantially improved yield (2.2-fold), indicating that both the carrier matrix and bacterial inoculation contributed to growth enhancement. These findings demonstrate the potential of biofertilizer technologies based on agri-food by-product valorization to improve crop performance under extreme and resource-limited agricultural conditions.
CUANTIFICACIÓN DE SAPONINAS EN RESIDUOS DE QUINUA REAL CHENOPODIUM QUINOA WILLD
(Lund University, 2012) Maribel Lozano; Edgar Freddy Quisbert Ticona; Cristhian Carrasco; Yonny Flores; Giovanna R. Almanza
"En el presente trabajo se realizó la cuantificación del rendimiento de extractos y de saponinas en residuos de escarificado generados en empresas exportadoras de quinua de los departamentos de La Paz, Oruro y Potosí, determinándose que los rendimientos de extracción varían desde 36,0 % hasta 39,4 % p/p, mientras que el porcentaje de saponinas en el extracto varía desde 47,3 % hasta 56,2 % y de saponinas en el mojuelo desde 17,3 % hasta 22,1 %. Adicionalmente, se optimizó un método de extracción de saponinas por maceración con mezclas hidroalcohólicas, considerando los siguientes parámetros: Relación masa/volumen de extracción; tiempo de extracción y relación porcentual EtOH/H2O (v/v), determinándose que la mejor relación m/v de extracción es 1/9. El tiempo de extracción óptimo es de 72 h y la mejor mezcla de extracción es con 50/50 EtOH/H2O. El porcentaje de saponinas se determinó utilizando los métodos de Espuma, Espectrofotométrico UV y por cromatografía HPLC, observándose que no hay grandes diferencias entre los 3 métodos aunque el método HPLC es el que tiene menos error y debería utilizarse como método de control para los otros métodos que son más baratos. Además, es muy importante utilizar como muestra de referencia un estándar de saponinas de quinua en todos los métodos."
Effects of Biosurfactants on Enzymatic Saccharification and Fermentation of Pretreated Softwood
(Multidisciplinary Digital Publishing Institute, 2020) Alfredo Oliva‐Taravilla; Cristhian Carrasco; Leif J. Jönsson; Carlos Martı́n
The enzymatic hydrolysis of cellulose is inhibited by non-productive adsorption of cellulases to lignin, and that is particularly problematic with lignin-rich materials such as softwood. Although conventional surfactants alleviate non-productive adsorption, using biosurfactants in softwood hydrolysis has not been reported. In this study, the effects of four biosurfactants, namely horse-chestnut escin, Pseudomonas aeruginosa rhamnolipid, and saponins from red and white quinoa varieties, on the enzymatic saccharification of steam-pretreated spruce were investigated. The used biosurfactants improved hydrolysis, and the best-performing one was escin, which led to cellulose conversions above 90%, decreased by around two-thirds lignin inhibition of Avicel hydrolysis, and improved hydrolysis of pretreated spruce by 24%. Red quinoa saponins (RQS) addition resulted in cellulose conversions above 80%, which was around 16% higher than without biosurfactants, and it was more effective than adding rhamnolipid or white quinoa saponins. Cellulose conversion improved with the increase in RQS addition up to 6 g/100 g biomass, but no significant changes were observed above that dosage. Although saponins are known to inhibit yeast growth, no inhibition of Saccharomyces cerevisiae fermentation of hydrolysates produced with RQS addition was detected. This study shows the potential of biosurfactants for enhancing the enzymatic hydrolysis of steam-pretreated softwood.
Exopolysaccharides Production by Cultivating a Bacterial Isolate from the Hypersaline Environment of Salar de Uyuni (Bolivia) in Pretreatment Liquids of Steam-Exploded Quinoa Stalks and Enzymatic Hydrolysates of Curupaú Sawdust
(Multidisciplinary Digital Publishing Institute, 2021) Diego Chambi; Luis Romero‐Soto; Roxana Villca; Felipe Orozco-Gutiérrez; José Roberto Vega‐Baudrit; Jorge Quillaguamán; Rajni Hatti‐Kaul; Carlos Martı́n; Cristhian Carrasco
The halotolerant bacterial strain BU-4, isolated from a hypersaline environment, was identified as an exopolysaccharide (EPS) producer. Pretreatment liquids of steam-exploded quinoa stalks and enzymatic hydrolysates of Curupaú sawdust were evaluated as carbon sources for EPS production with the BU-4 strain, and the produced EPS was characterized using FTIR, TGA, and SEM. Cultivation was performed at 30 °C for 48 h, and the cells were separated from the culture broth by centrifugation. EPS was isolated from the cell pellets by ethanol precipitation, and purified by trichloroacetic acid treatment, followed by centrifugation, dialysis, and freeze-drying. EPS production from quinoa stalks- and Curupaú sawdust-based substrates was 2.73 and 0.89 g L−1, respectively, while 2.34 g L−1 was produced when cultivation was performed on glucose. FTIR analysis of the EPS revealed signals typical for polysaccharides, as well as ester carbonyl groups and sulfate groups. High thermal stability, water retention capacity and gel-forming ability were inferred from SEM and TGA. The capability of the halotolerant isolate for producing EPS from pretreatment liquids and hydrolysates was demonstrated, and characterization of the EPS revealed their broad application potential. The study shows a way for producing value-added products from waste materials using a bacterium from a unique Bolivian ecosystem.
Extraction of Glucuronoarabinoxylan from Quinoa Stalks (Chenopodium quinoa Willd.) and Evaluation of Xylooligosaccharides Produced by GH10 and GH11 Xylanases
(American Chemical Society, 2017) Daniel Martín Salas-Veizaga; Rodrigo Villagomez; Javier A. Linares‐Pastén; Cristhian Carrasco; María Teresa Álvarez; Patrick Adlercreutz; Eva Nordberg Karlsson
Byproducts from quinoa are not yet well explored sources of hemicellulose or products thereof. In this work, xylan from milled quinoa stalks was retrieved to 66% recovery by akaline extraction using 0.5 M NaOH at 80 °C, followed by ethanol precipitation. The isolated polymer eluted as a single peak in size-exclusion chromatography with a molecular weight of >700 kDa. Analysis by Fourier transform infrared spectroscopy and nuclear magnetic resonance (NMR) combined with acid hydrolysis to monomers showed that the polymer was built of a backbone of β(1 → 4)-linked xylose residues that were substituted by 4-O-methylglucuronic acids, arabinose, and galactose in an approximate molar ratio of 114:23:5:1. NMR analysis also indicated the presence of α(1 → 5)-linked arabinose substituents in dimeric or oligomeric forms. The main xylooligosaccharides (XOs) produced after hydrolysis of the extracted glucuronoarabinoxylan polymer by thermostable glycoside hydrolases (GHs) from families 10 and 11 were xylobiose and xylotriose, followed by peaks of putative substituted XOs. Quantification of the unsubstituted XOs using standards showed that the highest yield from the soluble glucuronoarabinoxylan fraction was 1.26 g/100 g of xylan fraction, only slightly higher than the yield (1.00 g/100 g of xylan fraction) from the insoluble fraction (p < 0.05). No difference in yield was found between reactions in buffer or water (p > 0.05). This study shows that quinoa stalks represent a novel source of glucuronoarabinoxylan, with a substituent structure that allowed for limited production of XOs by GH10 or GH11 enzymes.
Fermentation of the Straw Material Paja Brava by the Yeast &lt;i&gt;Pichia stipitis&lt;/i&gt; in a Simultaneous Saccharification and Fermentation Process
(Scientific Research Publishing, 2013) Cristhian Carrasco; Henrique Macedo Baudel; Christian Roslander; Mats Galbe; Gunnar Lidén
Paja Brava is a native South American grass with a high carbohydrate content. In the current work, the potential of using this feedstock for ethanol production using a simultaneous saccharification and fermentation (SSF) process with the xylose-fermenting yeast Pichia stipitis (Scheffersomyces stipitis) CBS6054 was investigated. The straw material was subjected to SO2 catalyzed steam pretreatment at 200°C and 5 min residence time, which resulted in a solubilization of pentose sugars (mainly xylose) of 64% with only minor amounts of degradation products. The obtained material, including the pretreatment liquid, was subsequently hydrolyzed and fermented in an SSF process at microaerobic conditions using either a batch or a fed-batch process at a total water-insoluble solids loading of 10%. Overall yields of ethanol based on all available sugars of 0.24 g/g and 0.27 g/g were obtained for batch and fed-batch mode of operation, respectively. The higher yield in the fed-batch process coincided with a higher degree of conversion of the sugars in the liquid medium, in particular of arabinose, for which the conversion was doubled (from 48% to 97%).
Hydrothermal Pretreatment of Water-Extracted and Aqueous Ethanol-Extracted Quinoa Stalks for Enzymatic Saccharification of Cellulose
(Multidisciplinary Digital Publishing Institute, 2021) Cristhian Carrasco; Leif J. Jönsson; Carlos Martı́n
Auto-catalyzed hydrothermal pretreatment (A-HTP) and sulfuric-acid-catalyzed hydrothermal pretreatment (SA-HTP) were applied to quinoa stalks in order to reduce their recalcitrance towards enzymatic saccharification. Prior to pretreatment, quinoa stalks were extracted with either water or a 50:50 (v/v) ethanol–water mixture for removing saponins. Extraction with water or aqueous ethanol, respectively, led to removal of 52 and 75% (w/w) of the saponins contained in the raw material. Preliminary extraction of quinoa stalks allowed for a lower overall severity during pretreatment, and it led to an increase of glucan recovery in the pretreated solids (above 90%) compared with that of non-extracted quinoa stalks (73–74%). Furthermore, preliminary extraction resulted in enhanced hydrolysis of hemicelluloses and lower by-product formation during pretreatment. The enhancement of hemicelluloses hydrolysis by pre-extraction was more noticeable for SA-HTP than for A-HTP. As a result of the pretreatment, glucan susceptibility towards enzymatic hydrolysis was remarkably improved, and the overall conversion values were higher for the pre-extracted materials (up to 83%) than for the non-extracted ones (64–69%). Higher overall conversion was achieved for the aqueous ethanol-extracted quinoa stalks (72–83%) than for the water-extracted material (65–74%).
Influence of Sunlight Exposure and Traditional Dehydration on Chemical and Nutritional Properties of Oxalis tuberosa (oca) Tubers
(Springer Science+Business Media, 2025) Grover Castañeta; Daniela Miranda-Flores; Atma‐Sol Bustos; Rocío García; Erick Loayza; Cristhian Carrasco; Leslie Tejeda; Franco M. Cabrerizo; J. Mauricio Peñarrieta
Production of exopolysaccharides by halotolerant bacteria cultivated in hydrolysates of spent mushroom substrate and hydrothermally pretreated Jerusalem artichoke stalks
(Elsevier BV, 2025) Diego A. Miranda; Lucía Fernández; Knut Olav Strætkvern; Cristhian Carrasco; Carlos Martı́n; Luis A. Romero-Soto
Residual Brewing Yeast as Substrate for Co-Production of Cell Biomass and Biofilm Using Candida maltosa SM4
(Multidisciplinary Digital Publishing Institute, 2021) Vidal Flores-Copa; Luis Romero‐Soto; Danitza Xiomara Romero-Calle; María Teresa Álvarez-Aliaga; Felipe Orozco-Gutiérrez; José Roberto Vega‐Baudrit; Carlos Martı́n; Cristhian Carrasco
Candida maltosa was cultivated in the liquid phase of residual brewing yeast, a major brewery residue, to produce biomass and biofilm. Using response surface methodology, the effect of two variables at two different levels was investigated. The independent variables were agitation speed (at 100 and 200 rpm), and aeration (at 1 and 3 L min−1). Aeration was identified to be important for the production of both biomass and biofilm, while agitation was the only factor significantly affecting biofilm production. The maximal production of biofilm (2.33 g L−1) was achieved for agitation of 200 rpm and aeration of 1 L min−1, while the maximum for biomass (16.97 g L−1) was reached for 100 rpm agitation and 3 L min−1 air flow. A logistic model applied to predict the growth of C. maltosa in the exponential phase and the biofilm production, showed a high degree of agreement between the prediction and the actual biomass measured experimentally. The produced biofilms were further characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). FTIR allowed the identification of methyl, carbonyl ester and sulfate groups, and revealed the presence of uronic acid moieties and glycosidic bonds. Water-retention ability up to relatively high temperatures was revealed by TGA, and that makes the produced biofilm suitable for production of hydrogels. SEM also gave indications on the hydrogel-forming potential of the biofilm.
Resveratrol, phenolic antioxidants, and saccharides in South American red wines
(Dove Medical Press, 2018) Daniel E. Osorio-Macías; Pamela Vásquez; Cristhian Carrasco; Björn Bergenståhl; J. Mauricio Peñarrieta
Abstract: Wine is an important beverage with a long tradition, and its moderate consumption may be considered beneficial for human health. Although there are many studies regarding phenolic compounds in wines, there is a lack of information about antioxidants and phenolic content in South American wines. In this study, 35 South American red wines from four different countries, vintages 2004–2013, purchased at retail stores in La Paz, Bolivia, were studied. Resveratrol content, total antioxidant capacity (TAC) by the 2,2′-azino-bis(3-ethylbenzotiazoline-6-sulfonic acid) (ABTS) and ferric-reducing antioxidant power (FRAP) methods, total phenolic content (TPH), total flavonoids (TF), and main saccharides were assessed using the well-established spectrophotometric and high-performance liquid chromatography methods. The results ranged from 4 to 24 mmol/L for TAC determined by ABTS method and 14 to 43 mmol/L for TAC determined by FRAP method, 1600 to 3500 mg gallic acid equivalents/L for TPH, and 2 to 6 mmol catechin equivalents /L for TF. The resveratrol content ranged from 0.1 to 8 mg/L. Saccharides, glucose, and fructose content ranged from 0.4 to 10 g/L, 1.4 to 8.6 g/L, and 0.2 to 12 g/L, respectively. There was a high correlation among the different methods. The results showed that some wines growing at high altitude (>1500 meters above the sea level) have higher amounts of TAC and phenolic content, including resveratrol, while non-varietal wines showed the lowest values. It was also observed that the saccharose content in some wines was surprisingly high, suggesting saccharose dosing after fermentation. Keywords: ABTS, FRAP, high altitude, HPLC, PCA, Bolivia
<scp>SO2</scp>‐catalysed steam pretreatment of quinoa stalks
(Wiley, 2013) Cristhian Carrasco; Diego Cuno; Karin Carlqvist; Mats Galbe; Gunnar Lidén
Abstract BACKGROUND Quinoa is a pseudo‐cereal grown predominantly in South America. The quinoa stalks are lignocellulosic residues, which have a limited use today. The objective of the current study was to assess the potential of this material as a source of monosaccharides for fermentation purposes by means of steam pretreatment giving sugars from the hemicellulose part, and enzymatic hydrolysis of the solid fraction obtained. SO 2 catalysed steam pretreatment was carried out with a holding time of 5 min at temperatures between 180 and 220°C. The pretreatment was carried out at two different scales, a small reactor of size 0.5 L and a somewhat larger reactor of size 10 L, to allow comparison of scale effects in the pretreatment. RESULTS The highest xylose yield in the liquid phase, obtained after pretreatment at 210°C, was 80%. In the smaller scale unit, longer residence times were needed. The enzymatic hydrolysis, at an enzyme loading of 15 FPU g ‐1 glucan and a WIS loading of 2%, resulted in a glucose yield of 70% based on the original glucan. The overall sugar yield, including the xylan hydrolysed in the enzymatic treatment, at dilute conditions was 75%. CONCLUSIONS SO 2 catalysed pretreatment of quinoa straw followed by enzymatic hydrolysis gave a relatively good sugar yield. However, the yield obtained was somewhat lower than previously reported for similar materials, such as wheat straw and sugarcane bagasse, steam pretreated with SO 2 . © 2013 Society of Chemical Industry
SO2-catalyzed steam pretreatment and fermentation of enzymatically hydrolyzed sugarcane bagasse
(Elsevier BV, 2009) Cristhian Carrasco; Henrique Macedo Baudel; Johan Sendelius; Tobias Modig; Christian Roslander; Mats Galbe; Bärbel Hahn‐Hägerdal; G. Zacchi; Gunnar Lidén
Steam pretreatment and fermentation of the straw material “Paja Brava” using simultaneous saccharification and co-fermentation
(Elsevier BV, 2010) Cristhian Carrasco; Henrique Macedo Baudel; J. Mauricio Peñarrieta; Carlos Solano; Leslie Tejeda; Christian Roslander; Mats Galbe; Gunnar Lidén
Sustainable production of exopolysaccharides from quinoa stalk hydrolysates using halotolerant Bacillus swezeyi: fermentation kinetics and product characterization
(Wiley, 2025) Diego A. Miranda; Cristhian Carrasco; Luis Romero‐Soto; Jenny Lundqvist; Ola Sundman; Mattias Hedenström; András Gorzsás; Markus Broström; Leif J. Jönsson; Carlos Martı́n
Abstract Microbial exopolysaccharides (EPSs) have attracted increasing attention due to their versatile applications across diverse areas. However, large‐scale production of EPSs remains challenging due to the high production costs, primarily driven by the use of synthetic carbon sources. This study demonstrates the potential of quinoa stalk hydrolysates as a sustainable alternative for EPS production using a halotolerant bacterial strain that was isolated from a hypersaline environment and termed SU4M. The bacterial isolate was identified through 16S rRNA and gyrB sequencing as a Bacillus swezeyi strain, and was then cultivated in quinoa stalk hydrolysates. The hydrolysates were produced by acid‐catalyzed hydrothermal pretreatment using either sulfuric acid or phosphoric acid, followed by enzymatic saccharification. Fermentation experiments conducted in both shake flasks and bioreactors demonstrated that B. swezeyi SU4M utilized glucose from the hydrolysates efficiently, resulting in significantly higher biomass (5.1 ± 0.1 g L −1 ) and EPS production (1.2 ± <0.1 g L −1 ) compared to synthetic media (4.3 ± 0.1 g L −1 and 1.1 ± <0.1 g L −1 ). The kinetic analysis revealed distinct substrate consumption rates and growth patterns, with hydrolysates enhancing EPS yields under single‐pulse fed‐batch conditions. Advanced characterization techniques, including compositional analysis, Fourier transform infrared (FTIR) spectroscopy, 1 H and 1 H‐ 13 C heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR), high‐performance size‐exclusion chromatography (HPSEC), and thermogravimetric analysis (TGA), confirmed that the EPSs derived from hydrolysates were heteropolysaccharides with close structural similarities to those obtained from synthetic media. These findings underscore the potential of quinoa stalk hydrolysates as a biobased alternative to synthetic media as a substrate for EPS production.
UN ESTUDIO EXPERIMENTAL DE PROPIEDADES FÍSICAS DE SAPONINAS Y SU INTERACCIÓN CON UN MODELO DE MEMBRANA DE BACTERIAS GRAM-NEGATIVAS EMPLEANDO PELÍCULAS LANGMUIR-BLODGETT Y MICROSCOPÍA DE FUERZA ATÓMICA
(2024) C. López Mejía; Ticona Ticona; ALMANZA; Cristhian Carrasco; Flavio Ghezzi
Saponins are non-ionic biosurfactants that exhibit antifungal, antiviral and antibacterial properties. However, the mechanisms by which saponins exhibits these properties are not well understood. In the present work, Langmuir and atomic force microscopy (AFM) techniques were employed to investigate the interactions of saponins with a model of Gramnegative bacterial membranes. The lipid films contained extracts of phosphatidylethanolamine and phosphatidylglycerol from Escherichia coli bacteria. The results suggest that saponins repel phospholipids, thereby increasing membrane fluidity. They also showed evidence of adsorption of the saponin by the membrane model. These results were cross-checked with AFM images. A mechanism for how saponin alters the phospholipid membrane is proposed. Langmuir technique and atomic force microscopy proved to be useful tools to investigate the interaction of biologically relevant compounds with cell membrane models. The results of the surface pressure measurements, combined with those obtained from AFM, provided evidence for the susceptibility of membranes to the insertion of saponins and their possible modes of action. The results of this study may contribute to a better understanding of the mechanisms of antifungal, antiviral and antibacterial activity of saponins