Predominant Yeasts During Artisanal Mezcal Fermentation and Their Capacity to Ferment Maguey Juice

Artisanal mezcal is produced by the natural fermentation of maguey juice, which frequently results in a process that becomes stuck or is sluggish. Using selected indigenous starter inoculums of Saccharomyces and non-Saccharomyces yeasts is considered beneficial in overcoming these problems and thereby preserving the essence of the artisanal process. In this work, three hundred and four yeast isolates were recovered from 17 distilleries and then grouped by the ARDRA analysis, their restriction profiles were clustered in 15 groups. Four of them included 90% of all isolates, and these were identified using the sequence of the D1/D2 domain of the large-subunit rDNA. Pichia kudriavzevii, Pichia manshurica, Saccharomyces cerevisiae, and Kluyveromyces marxianus were detected as predominant species. Both species belonging to the Pichia genus were detected in 88% of the distilleries, followed by S. cerevisiae (70%) and K. marxianus (50%). In order to evaluate the fermentative capacity, one strain of each species was assessed in a pure and mixed culture in two culture media, filtered maguey juice (MJ) and maguey juice including its bagasse (MJB). Findings demonstrated that non-Saccharomyces yeast presented better growth than that of S. cerevisiae. K. marxianus PA16 was more efficient for ethanol production than S. cerevisiae DI14. It produced 32 g/L of ethanol with a yield of 0.47 g/g and efficient of 90%. While, P. kudriavzevii produced more ethyl acetate (280 mg/L) than the others species. All fermentations were characterized by the presence of isobutyl and isoamyl alcohol. The presence of K. marxianus in a mixed culture, improved the ethanol production and volatile compounds increased using co-cultures

Lactic Acid Fermentation of Arabinoxylan From Nejayote by Streptococcus infantarius ssp. infantarius 25124 Isolated From Pozol

Streptococcus infantarius ssp. infantarius 25124 (Sii-25124) is a lactic acid bacterium (LAB) isolated from pozol, a refreshing beverage prepared by suspending fermented nixtamal (a thermal and alkali-treated maize dough) in water. Although Lactobacillus are the predominant strains in fermented doughs, such as sourdoughs, and non-nixtamalized fermented maize foods, the pozol microbiota is markedly different. This may be the result of the nixtamalization process, which could act as a selective force of some strains. Sii-25124 has been reported as the main amylolytic LAB in pozol; starch is the primary carbon source on nixtamal since monosaccharides and disaccharides are lost during nixtamalization; however, non-amylolytic LAB counts are higher than amylolytic LAB in pozol after 24-h fermentation suggesting that another carbon source is being used by the former bacteria. Hemicellulose (arabinoxylan in maize) becomes available via nixtamalization and is subsequently metabolized by LAB. The aim of this work was to determine whether this bacterium is able to use arabinoxylan as the only carbon source in a defined medium containing arabinoxylan extracted from either nejayote (wash water produced during nixtamal preparation), or beechwood xylan. Xylanase activity in the presence of nejayote arabinoxylan (135.8 ± 48.7 IU/mg protein) was higher than that of beechwood (62.5 ± 19.8 IU/mg protein). Other enzymatic activities, such as arabinofuranosidase and acetyl esterase, were also detected, suggesting the adaptation of the bacterium studied to nixtamal dough. It was concluded that Streptococcus infantarius 25124 isolated from pozol was able to use arabinoxylans, which are present in nixtamal dough, so fermentation does not depend exclusively on free sugars and starch

Former food biotechnology: fermented foods

Tema del mesCuando el ser humano se volvió sedentario desarrolló el cultivo de plantas y el cuidado de animales para alimentarse. Se vio entonces en la necesidad de conservarlos y descubrió que en algunos casos los alimentos se modificaban transformándose en productos que no sólo resultaban estables, sino que además eran agradables al gusto y no los enfermaban. Se piensa que así empezaron a "domesticarse" los procesos para producir alimentos fermentados, alimentos que vinieron a dar una importante variedad nutrimental a la dieta, al tiempo que se incorporaba de manera empírica a las levaduras, los hongos y las bacterias a la tarea de producción de alimentos. Entre las muy diversas evidencias de esta actividad, se puede citar el decorado con dibujos que representan alimentos e ingredientes de recipientes usados para cocinar en esa época, además de lo descrito posteriormente en los códices, en los que se destaca por ejemplo el proceso de elaboración del pulque. De esta forma, es interesante resaltar que así como la agricultura nació de manera simultánea en diferentes partes del mundo, surgieron también de forma simultánea los procesos de fermentación derivados de la transformación microbiológica de cereales y frutas: trigo, cebada y arroz en el viejo continente, maíz en Mesoamérica; cerveza y vino en el primero; pozol, y pulque en el segundo. En Mesoamérica, el maíz, además de ser la base de la alimentación, quedó profundamente arraigado a nuestra cultura, al grado de considerar, como se describe en el Popol Vuh y en otros documentos antiguos, que los dioses decidieron hacer a los mesoamericanos de maíz. Muchos de estos productos se han preservado a lo largo de los siglos, conservando también su carácter artesanal. Por diversas circunstancias, no es sino hasta hace unas cuantas décadas que se analiza con profundidad el tipo de microorganismos responsables de lo que podríamos considerar los alimentos fermentados prehispánicos. Muchos de estos microorganismos, además de presentar actividades fisiológicas interesantes, podrían usarse como cultivos iniciadores para producir estos alimentos en condiciones controladas. Es un reto importante para la biotecnología moderna nacional aprovechar los procesos y el conocimiento derivado de los alimentos que se originaron en el pasado para mejorar los que se producen en la actualidad.When human beings became sedentary creatures, agriculture and animal raising where invented as means to supply for their alimentary needs. Then arose the question of food preservation and ancient cultures soon discovered that, in some cases, food could be transformed over time to become stable, healthy and even tasty nutritional goods. It is said that this is how the "domestication" of fermented food was invented. These kind of fermented products became an important part of ancient diets: yeast, bacteria and fungus where then empirically incorporated to the process of food production. There is a considerable amount of evidence, in decorative drawings for instance, that represent the ingredients and tools used in this process as well as the posterior description in codex of the elaboration of products such as "pulque". In the same way as agriculture was established in different cultures, the fermenting process of microbiological transformation of cereals and fruit appeared simultaneously around the ancient world: wheat, barley and rice producing wine and beer in Europe, and corn for "pozol" and "pulque" in our continent. Furthermore, in the Mesoamerican region, corn became a profound cultural value to the extent that the Popol Vuh and other ancient documents state that Mesoamerican men were created from this cereal. Many of these culinary products are still in use preserving their traditional background. Even so, the systematic studies of microorganisms at the base of fermented prehispanic food products are recent and incomplete. Besides the physiological interest that these microorganisms may arise, they can be used as means to create fermented products in controlled environments. It is thus an important challenge for national biotechnology to profit from the acquainted knowledge bestowed by this kind of ancient process for the improved of actual food production

Microorganisms and chocolate

Tema del mesLos granos de cacao tienen un sabor ácido desagradable, por lo que para obtener cacao con el color y el sabor del chocolate deben ser fermentados, tostados y secados. En el proceso de fermentación participan los microorganismos que se encuentran naturalmente en los granos, de entre los cuales actúan primeramente las levaduras. Posteriormente actúan las bacterias lácticas y, finalmente, intervienen las bacterias acéticas, los Bacillus y las enterobacterias. Esta fermentación es esencial tanto para modificar los granos, eliminando el mucílago, como para preparar el grano que requieren las enzimas encargadas de modificar su color, sabor y olor, produciendo también compuestos de sabor. La fermentación es una etapa del procesamiento del grano de cacao, que requiere aún de investigación, ya que hasta la fecha sigue siendo bastante empírica. Una fermentación en condiciones controladas permitirá obtener cacao de buena calidad y de características homogéneasCocoa grains must be fermented, roasted and dried in order to obtain the color and flavor of chocolate, form the original unpleasant acid flavor of the beans. Microorganisms naturally present in the grains participate in the fermentation process that involves the sequential action of yeasts, lactic acid bacteria and finally acetic acid bacteria, different species of Bacillus and of enterobacteria. Fermentation is essential to remove the mucilage and to prepare the grains for the enzyme modification of its color and flavor, as well as to produce flavor compounds. Further studies on the fermentation are needed to be able to perform it under controlled conditions in order to obtain cocoa of high and constant qualit

Lactobacillus cypricasei sp. nov., isolated from halloumi cheese

Four strains of a hitherto unknown bacterium isolated from Halloumi cheese were compared by using phenotypic and phylogenetic studies. Comparative 16S rRNA gene sequencing demonstrated that the strains were identical to each other and represent a new subline within the genus Lactobacillus. The unknown bacterium was readily distinguished from other described Gram-positive catalase-negative taxa by means of biochemical tests and electrophoretic analysis of whole-cell proteins. On the basis of phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Lactobacillus cypricasei sp. nov. The type strain of L. cypricasei is CCUG 42961T ( = CIP 106393T

Microbial Interactions between Amylolytic and Non-Amylolytic Lactic Acid Bacteria Strains Isolated during the Fermentation of Pozol

Pozol is a Mexican beverage prepared from fermented nixtamalized maize dough. To contribute to understanding its complex microbial ecology, the effect of inoculating on MRS-starch pure and mixed cultures of amylolytic Sii-25124 and non-amylolytic W. confusa 17, isolated from pozol, were studied on their interactions and fermentation parameters. These were compared with L. plantarum A6, an amylolytic strain isolated from cassava. Microbial growth, kinetic parameters, amylolytic activity, lactic acid production, and hydrolysis products from starch fermentation were measured. The population dynamics were followed by qPCR. L. plantarum A6 showed higher enzymatic activity, lactic acid, biomass production, and kinetic parameters than pozol LAB in pure cultures. Mixed culture of each pozol LAB with L. plantarum A6 showed a significant decrease in amylolytic activity, lactic acid yield, specific growth rate, and specific rate of amylase production. The interaction between Sii-25124 and W. confusa 17 increased the global maximum specific growth rate (µ), the lactic acid yield from starch (Ylac/s), lactic acid yield from biomass (Ylac/x), and specific rate of lactic acid production (qlac) by 15, 30, 30, and 40%, respectively, compared with the pure culture of Sii-25124. Interactions between the two strains are essential for this fermentation

Probiotic properties and stress response of thermotolerant lactic acid bacteria isolated from cooked meat products

29 p.-5 fig.-1 tabThe aim of this study was to evaluate the probiotic properties of six thermotolerant lactic acid bacteria isolated from cooked meat products. The bacteria were typed, by determination of the DNA sequence of their 16S rRNA coding genes, as one Enterococcus faecium (UAM1 strain) and five Pediococcus pentosaceus (UAM2-UAM6 strains). Under gastric stress conditions the viability of the Pediococci decreased more than five-fold, whereas E. faecium showed a high resistance (61% survival). Exposure to small intestine stress did not drastically affect the survival of any of the strains (less than one-fold decrease), which were able to grow in the presence of 0.3% bile. A hydrophilic surface profile was observed, with higher affinity for chloroform than for xylene. Strains showed high levels of auto-aggregation as well as co-aggregation with Gram-positive and Gram-negative bacterial pathogens. The adherence of E faecium UAM1 to human Caco-2 cells (around 20%) was significantly higher than that obtained with the P. pentosaceus strains (2%–5%) and Lactobacillus acidophilus LA-5 (6%). The overall results indicate that E. faecium UAM1, has probiotic properties that predict its capability to colonize in competition with pathogens in the intestinal tract. This bacterium deserves further investigation for its potential as a component of functional food.A. M. Hernández-Alcántara was supported by graduate grants from the Consejo Nacional de Ciencia y Tecnología (CONACyT) Mexico (National Grant 290817 and Mixed Grant 291062). This work was also supported by the Spanish Ministry of Economy and Competitiveness (grant AGL2015-65010-C3-1-R).Peer reviewe

Frecuencia de contaminación y de serotipos de Salmonella enterica y Escherichia coli en una operación integrada de matanza y deshuese de bovinos

This study aimed to determine the frequency of contamination and serovar diversity of Salmonella enterica (SE) and Escherichia coli (EC) in different stages of cattle slaughtering and deboning processes. Fecal, carcass, and primal cut (100 of each type) samples were collected in a Federally Inspected slaughterhouse in Mexicali, Baja California. EC was not analyzed in fecal samples because it is part of the gut microbiota. Strain identity was confirmed by biochemical methods and PCR, using the taxonomic genes invA and gadA for SE and EC, respectively. In EC, the presence of genes associated with the main pathotypes was also investigated. SE had a 34 % frequency in fecal samples, 3% in carcasses, and 2% in cuts, while Montevideo was the predominant serovar (72.5 % of the total strains). EC was detected in carcasses (34 %) and cuts (11 %) at an average concentration of 0.012 and 0.33 log CFU cm-2, respectively. Although several of the identified EC serovars were associated with enterotoxigenic or Shiga toxin-producing strains, none carried the virulence factors typically observed in these pathotypes. In summary, beef carcasses and cuts are not a relevant source of EC pathogenic strains. However, beef is an important reservoir of SE, which represents a public health risk. Genomic studies are required on the virulence profile and genes of SE strains commonly associated with subclinical infections and isolated from apparently healthy animals.El objetivo fue determinar la frecuencia de contaminación y la diversidad de serotipos de Salmonella enterica (SE) y Escherichia coli (EC) en diferentes etapas de los procesos de matanza y deshuese de bovinos. Se tomaron muestras de heces, canales y cortes primarios (100 de cada tipo) en un rastro Tipo Inspección Federal ubicado en Mexicali, Baja California. EC no se analizó en heces, por ser esta bacteria parte de la microbiota intestinal. La identidad de las cepas se confirmó por métodos bioquímicos y por PCR: genes taxonómicos invA y gadA, para SE y EC, respectivamente. En EC se investigó también la presencia de genes asociados con los principales patotipos. SE tuvo una frecuencia de 34 % en heces, 3 % en canales y 2 % en cortes, siendo Montevideo el serotipo predominante (72.5 % del total de cepas). EC se detectó en canales (34 %) y en cortes (11 %), en concentraciones promedio de 0.012 y 0.33 log UFC cm-2, respectivamente. Aunque varios de los serotipos de EC identificados están asociados con cepas enterotoxigénicas o productoras de toxinas tipo Shiga, ninguno portaba factores de virulencia característicos de estos patotipos. En resumen, las canales y cortes de bovino no son una fuente relevante de cepas patógenas de EC. En contraste, los bovinos constituyen un importante reservorio de SE, lo cual representa un riesgo para la salud pública. Se requieren estudios genómicos sobre el perfil de virulencia y los genes asociados con infecciones subclínicas en cepas de SE provenientes de animales aparentemente sano