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Papers by Mariela Serrano
<b>Copyright information:</b>Taken from "Thioredoxin reductase is a key factor i... more <b>Copyright information:</b>Taken from "Thioredoxin reductase is a key factor in the oxidative stress response of WCFS1"http://www.microbialcellfactories.com/content/6/1/29Microbial Cell Factories 2007;6():29-29.Published online 28 Aug 2007PMCID:PMC2174512. The strain NZ7601 was grown (black bars) aerobically and (gray bars) anaerobically at 37°C and was induced with 0 or 50 ng/ml nisinZ. After 5 hours of induction cell free extracts were prepared and TR activity was measured. The data shown above is the result of three independent experiments.
Microbial Cell Factories, 2007
Background Thioredoxin (TRX) is a powerful disulfide oxido-reductase that catalyzes a wide spectr... more Background Thioredoxin (TRX) is a powerful disulfide oxido-reductase that catalyzes a wide spectrum of redox reactions in the cell. The aim of this study is to elucidate the role of the TRX system in the oxidative stress response in Lactobacillus plantarum WCFS1. Results We have identified the trxB1-encoded thioredoxin reductase (TR) as a key enzyme in the oxidative stress response of Lactobacillus plantarum WCFS1. Overexpression of the trxB1 gene resulted in a 3-fold higher TR activity in comparison to the wild-type strain. Subsequently, higher TR activity was associated with an increased resistance towards oxidative stress. We further determined the global transcriptional response to hydrogen peroxide stress in the trxB1-overexpression and wild-type strains grown in continuous cultures. Hydrogen peroxide stress and overproduction of TR collectively resulted in the up-regulation of 267 genes. Additionally, gene expression profiling showed significant differential expression of 27 g...
Applied and Environmental Microbiology, 2017
Functional starter cultures demonstrating superior technological and food safety properties are a... more Functional starter cultures demonstrating superior technological and food safety properties are advantageous to the food fermentation industry. We evaluated the efficacies of single- and double-bacteriocin-producing starters of Lactococcus lactis capable of producing the class I bacteriocins nisin A and/or lacticin 3147 in terms of starter performance. Single producers were generated by mobilizing the conjugative bacteriophage resistance plasmid pMRC01, carrying lacticin genetic determinants, or the conjugative transposon Tn 5276 , carrying nisin genetic determinants, to the commercial starter L. lactis CSK2775. The effect of bacteriocin coproduction was examined by superimposing pMRC01 into the newly constructed nisin transconjugant. Transconjugants were improved with regard to antimicrobial activity and bacteriophage insensitivity compared to the recipient strain, and the double producer was immune to both bacteriocins. Bacteriocin production in the starter was stable, although th...
Microbiology Resource Announcements
Lactococcus lactis is a Gram-positive lactic acid bacterium commonly used in the dairy industry f... more Lactococcus lactis is a Gram-positive lactic acid bacterium commonly used in the dairy industry for the production of fermented foods such as buttermilk and a wide variety of cheeses. Here, we report the complete genome sequences of 28 bacteriophages infecting different L. lactis industrial starter strains isolated from dairy plants throughout the world.
Journal of dairy science, 2017
We assessed the efficacy of Lactobacillus nodensis CSK964 as an adjunct culture in Gouda cheese u... more We assessed the efficacy of Lactobacillus nodensis CSK964 as an adjunct culture in Gouda cheese under various industrial conditions. We set up 4 different systems: a direct vat inoculum with and without adjunct using the calf rennet Kalase, and an undefined bulk starter culture with and without adjunct using the microbial rennet Milase (both rennets from CSK Food Enrichment, Ede, the Netherlands). During ripening, we subjected the cheeses to the following analyses: viability of starter and adjunct cells, composition, proteolysis, and flavor development by detection of sulfur compounds and descriptive sensory analysis. In general, the presence of Lb. nodensis increased secondary proteolysis and influenced cheese flavor, particularly in relation to volatile sulfur compounds; hydrogen sulfide and methanethiol were present in higher abundances in cheeses containing Lb. nodensis. The primary starter also influenced the range of volatile sulfur compounds produced. Methanethiol and dimethy...
Avances en Ciencias e Ingeniería, 2014
&amp;lt;p&amp;gt;En 20 provincias ecuatorianas, se colectaron 91 muestras de alim... more &amp;lt;p&amp;gt;En 20 provincias ecuatorianas, se colectaron 91 muestras de alimentos fermentados preparados de forma artesanal con el objetivo de identificar cepas con uso potencial en la producción de alimentos fermentados. Se aislaron 119 cepas que fueron caracterizadas a través de pruebas fenotípicas y secuenciamiento del ADN ribosomal 16S. Del total de cepas aisladas, 47% fueron &amp;lt;em&amp;gt;Lactobacillus sp&amp;lt;/em&amp;gt;. heterofermentadores facultativos, 31% fueron cocos homofermentadores pertenecientes a los géneros &amp;lt;em&amp;gt;Pediococcus, Lactococcus&amp;lt;/em&amp;gt; y &amp;lt;em&amp;gt;Enterococcus&amp;lt;/em&amp;gt;, 11% fueron &amp;lt;em&amp;gt;Lactobacillus sp&amp;lt;/em&amp;gt;. heterofermentadores obligados y el 11% restante cocos heterofermentadores de los géneros &amp;lt;em&amp;gt;Weissella&amp;lt;/em&amp;gt; y &amp;lt;em&amp;gt;Leuconostoc&amp;lt;/em&amp;gt;. Algunas cepas presentaron ciertas propiedades con posible aplicación en la industria alimentaria como actividad caseinolítica y la producción exopolisacárido y bacteriocinas.&amp;lt;/p&amp;gt;
Microbial Cell Factories, 2015
Background: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic ba... more Background: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic bacterium with proven health benefits upon oral intake, including the alleviation of diarrhea. The mission of the Yoba for Life foundation is to provide impoverished communities in Africa increased access to Lactobacillus rhamnosus GG under the name Lactobacillus rhamnosus yoba 2012, world's first generic probiotic strain. We have been able to overcome the strain's limitations to grow in food matrices like milk, by formulating a dried starter consortium with Streptococcus thermophilus that enables the propagation of both strains in milk and other food matrices. The affordable seed culture is used by people in resource-poor communities. Results: We used S. thermophilus C106 as an adjuvant culture for the propagation of L. rhamnosus yoba 2012 in a variety of fermented foods up to concentrations, because of its endogenous proteolytic activity, ability to degrade lactose and other synergistic effects. Subsequently, L. rhamnosus could reach final titers of 1E+09 CFU ml −1 , which is sufficient to comply with the recommended daily dose for probiotics. The specific metabolic interactions between the two strains were derived from the full genome sequences of L. rhamnosus GG and S. thermophilus C106. The piliation of the L. rhamnosus yoba 2012, required for epithelial adhesion and inflammatory signaling in the human host, was stable during growth in milk for two rounds of fermentation. Sachets prepared with the two strains, yoba 2012 and C106, retained viability for at least 2 years. Conclusions: A stable dried seed culture has been developed which facilitates local and low-cost production of a wide range of fermented foods that subsequently act as delivery vehicles for beneficial bacteria to communities in east Africa.
Genome announcements, Jan 25, 2015
The lactic acid bacterium Streptococcus thermophilus is widely used for the fermentation of dairy... more The lactic acid bacterium Streptococcus thermophilus is widely used for the fermentation of dairy products. Here, we present the draft genome sequence of S. thermophilus C106 isolated from an artisanal cheese produced in the countryside of Ireland.
"April 28, 2000." Typescript. "The report of the investigation undertaken as a sen... more "April 28, 2000." Typescript. "The report of the investigation undertaken as a senior thesis, to carry one course of credit in the Department of Chemistry." Thesis (B.A.)--Lake Forest College, 2000. With distinction. Includes bibliographical references.
Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a poten... more Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a potent class IIa bacteriocin with 100% homology to plantaricin 423 and bacteriocidal activity against Listeria innocua and Listeria monocytogenes. The bacteriocin was found to be highly stable at temperatures as high as 100°C and pH ranges from 1-10. While this relatively narrow spectrum bacteriocin also exhibited antimicrobial activity against species of enterococci, it did not inhibit dairy starters including lactococci and lactobacilli when tested by well diffusion assay (WDA). In order to test the suitability of Lb. plantarum LMG P-26358 as an anti-listerial adjunct with nisin-producing lactococci, laboratory-scale cheeses were manufactured. Results indicated that combining Lb. plantarum LMG P-26358 (at 10 8 colony forming units (cfu)/ml) with a nisin producer is an effective strategy to eliminate the biological indicator strain, L. innocua. Moreover, industrial-scale cheeses also demonstrated that Lb. plantarum LMG P-26358 was much more effective than the nisin producer alone for protection against the indicator. MALDI-TOF mass spectrometry confirmed the presence of plantaricin 423 and nisin in the appropriate cheeses over an 18 week ripening period. A spray-dried fermentate of Lb. plantarum LMG P-26358 also demonstrated potent antilisterial activity in vitro using L. innocua. Overall, the results suggest that Lb. plantarum LMG P-26358 is a suitable adjunct for use with nisin-producing cultures to improve the safety and quality of dairy products.
<b>Copyright information:</b>Taken from "Thioredoxin reductase is a key factor i... more <b>Copyright information:</b>Taken from "Thioredoxin reductase is a key factor in the oxidative stress response of WCFS1"http://www.microbialcellfactories.com/content/6/1/29Microbial Cell Factories 2007;6():29-29.Published online 28 Aug 2007PMCID:PMC2174512. The strain NZ7601 was grown (black bars) aerobically and (gray bars) anaerobically at 37°C and was induced with 0 or 50 ng/ml nisinZ. After 5 hours of induction cell free extracts were prepared and TR activity was measured. The data shown above is the result of three independent experiments.
Microbial Cell Factories, 2007
Background Thioredoxin (TRX) is a powerful disulfide oxido-reductase that catalyzes a wide spectr... more Background Thioredoxin (TRX) is a powerful disulfide oxido-reductase that catalyzes a wide spectrum of redox reactions in the cell. The aim of this study is to elucidate the role of the TRX system in the oxidative stress response in Lactobacillus plantarum WCFS1. Results We have identified the trxB1-encoded thioredoxin reductase (TR) as a key enzyme in the oxidative stress response of Lactobacillus plantarum WCFS1. Overexpression of the trxB1 gene resulted in a 3-fold higher TR activity in comparison to the wild-type strain. Subsequently, higher TR activity was associated with an increased resistance towards oxidative stress. We further determined the global transcriptional response to hydrogen peroxide stress in the trxB1-overexpression and wild-type strains grown in continuous cultures. Hydrogen peroxide stress and overproduction of TR collectively resulted in the up-regulation of 267 genes. Additionally, gene expression profiling showed significant differential expression of 27 g...
Applied and Environmental Microbiology, 2017
Functional starter cultures demonstrating superior technological and food safety properties are a... more Functional starter cultures demonstrating superior technological and food safety properties are advantageous to the food fermentation industry. We evaluated the efficacies of single- and double-bacteriocin-producing starters of Lactococcus lactis capable of producing the class I bacteriocins nisin A and/or lacticin 3147 in terms of starter performance. Single producers were generated by mobilizing the conjugative bacteriophage resistance plasmid pMRC01, carrying lacticin genetic determinants, or the conjugative transposon Tn 5276 , carrying nisin genetic determinants, to the commercial starter L. lactis CSK2775. The effect of bacteriocin coproduction was examined by superimposing pMRC01 into the newly constructed nisin transconjugant. Transconjugants were improved with regard to antimicrobial activity and bacteriophage insensitivity compared to the recipient strain, and the double producer was immune to both bacteriocins. Bacteriocin production in the starter was stable, although th...
Microbiology Resource Announcements
Lactococcus lactis is a Gram-positive lactic acid bacterium commonly used in the dairy industry f... more Lactococcus lactis is a Gram-positive lactic acid bacterium commonly used in the dairy industry for the production of fermented foods such as buttermilk and a wide variety of cheeses. Here, we report the complete genome sequences of 28 bacteriophages infecting different L. lactis industrial starter strains isolated from dairy plants throughout the world.
Journal of dairy science, 2017
We assessed the efficacy of Lactobacillus nodensis CSK964 as an adjunct culture in Gouda cheese u... more We assessed the efficacy of Lactobacillus nodensis CSK964 as an adjunct culture in Gouda cheese under various industrial conditions. We set up 4 different systems: a direct vat inoculum with and without adjunct using the calf rennet Kalase, and an undefined bulk starter culture with and without adjunct using the microbial rennet Milase (both rennets from CSK Food Enrichment, Ede, the Netherlands). During ripening, we subjected the cheeses to the following analyses: viability of starter and adjunct cells, composition, proteolysis, and flavor development by detection of sulfur compounds and descriptive sensory analysis. In general, the presence of Lb. nodensis increased secondary proteolysis and influenced cheese flavor, particularly in relation to volatile sulfur compounds; hydrogen sulfide and methanethiol were present in higher abundances in cheeses containing Lb. nodensis. The primary starter also influenced the range of volatile sulfur compounds produced. Methanethiol and dimethy...
Avances en Ciencias e Ingeniería, 2014
&amp;lt;p&amp;gt;En 20 provincias ecuatorianas, se colectaron 91 muestras de alim... more &amp;lt;p&amp;gt;En 20 provincias ecuatorianas, se colectaron 91 muestras de alimentos fermentados preparados de forma artesanal con el objetivo de identificar cepas con uso potencial en la producción de alimentos fermentados. Se aislaron 119 cepas que fueron caracterizadas a través de pruebas fenotípicas y secuenciamiento del ADN ribosomal 16S. Del total de cepas aisladas, 47% fueron &amp;lt;em&amp;gt;Lactobacillus sp&amp;lt;/em&amp;gt;. heterofermentadores facultativos, 31% fueron cocos homofermentadores pertenecientes a los géneros &amp;lt;em&amp;gt;Pediococcus, Lactococcus&amp;lt;/em&amp;gt; y &amp;lt;em&amp;gt;Enterococcus&amp;lt;/em&amp;gt;, 11% fueron &amp;lt;em&amp;gt;Lactobacillus sp&amp;lt;/em&amp;gt;. heterofermentadores obligados y el 11% restante cocos heterofermentadores de los géneros &amp;lt;em&amp;gt;Weissella&amp;lt;/em&amp;gt; y &amp;lt;em&amp;gt;Leuconostoc&amp;lt;/em&amp;gt;. Algunas cepas presentaron ciertas propiedades con posible aplicación en la industria alimentaria como actividad caseinolítica y la producción exopolisacárido y bacteriocinas.&amp;lt;/p&amp;gt;
Microbial Cell Factories, 2015
Background: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic ba... more Background: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic bacterium with proven health benefits upon oral intake, including the alleviation of diarrhea. The mission of the Yoba for Life foundation is to provide impoverished communities in Africa increased access to Lactobacillus rhamnosus GG under the name Lactobacillus rhamnosus yoba 2012, world's first generic probiotic strain. We have been able to overcome the strain's limitations to grow in food matrices like milk, by formulating a dried starter consortium with Streptococcus thermophilus that enables the propagation of both strains in milk and other food matrices. The affordable seed culture is used by people in resource-poor communities. Results: We used S. thermophilus C106 as an adjuvant culture for the propagation of L. rhamnosus yoba 2012 in a variety of fermented foods up to concentrations, because of its endogenous proteolytic activity, ability to degrade lactose and other synergistic effects. Subsequently, L. rhamnosus could reach final titers of 1E+09 CFU ml −1 , which is sufficient to comply with the recommended daily dose for probiotics. The specific metabolic interactions between the two strains were derived from the full genome sequences of L. rhamnosus GG and S. thermophilus C106. The piliation of the L. rhamnosus yoba 2012, required for epithelial adhesion and inflammatory signaling in the human host, was stable during growth in milk for two rounds of fermentation. Sachets prepared with the two strains, yoba 2012 and C106, retained viability for at least 2 years. Conclusions: A stable dried seed culture has been developed which facilitates local and low-cost production of a wide range of fermented foods that subsequently act as delivery vehicles for beneficial bacteria to communities in east Africa.
Genome announcements, Jan 25, 2015
The lactic acid bacterium Streptococcus thermophilus is widely used for the fermentation of dairy... more The lactic acid bacterium Streptococcus thermophilus is widely used for the fermentation of dairy products. Here, we present the draft genome sequence of S. thermophilus C106 isolated from an artisanal cheese produced in the countryside of Ireland.
"April 28, 2000." Typescript. "The report of the investigation undertaken as a sen... more "April 28, 2000." Typescript. "The report of the investigation undertaken as a senior thesis, to carry one course of credit in the Department of Chemistry." Thesis (B.A.)--Lake Forest College, 2000. With distinction. Includes bibliographical references.
Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a poten... more Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a potent class IIa bacteriocin with 100% homology to plantaricin 423 and bacteriocidal activity against Listeria innocua and Listeria monocytogenes. The bacteriocin was found to be highly stable at temperatures as high as 100°C and pH ranges from 1-10. While this relatively narrow spectrum bacteriocin also exhibited antimicrobial activity against species of enterococci, it did not inhibit dairy starters including lactococci and lactobacilli when tested by well diffusion assay (WDA). In order to test the suitability of Lb. plantarum LMG P-26358 as an anti-listerial adjunct with nisin-producing lactococci, laboratory-scale cheeses were manufactured. Results indicated that combining Lb. plantarum LMG P-26358 (at 10 8 colony forming units (cfu)/ml) with a nisin producer is an effective strategy to eliminate the biological indicator strain, L. innocua. Moreover, industrial-scale cheeses also demonstrated that Lb. plantarum LMG P-26358 was much more effective than the nisin producer alone for protection against the indicator. MALDI-TOF mass spectrometry confirmed the presence of plantaricin 423 and nisin in the appropriate cheeses over an 18 week ripening period. A spray-dried fermentate of Lb. plantarum LMG P-26358 also demonstrated potent antilisterial activity in vitro using L. innocua. Overall, the results suggest that Lb. plantarum LMG P-26358 is a suitable adjunct for use with nisin-producing cultures to improve the safety and quality of dairy products.