Dominant yeasts associated to mango (Mangifera indica) and rose apple (Syzygium malaccense) fruit pulps investigated by culture-based methods.

The biotechnological potential of yeasts associated to different habitats in Colombia has been poorly studied, especially the yeasts associated with different plant structures. Fruit pulps are interesting substrates mainly for the growth of yeast species, that can positively affect the productivity and quality of some bioeconomic species. Therefore, the objective of this study was to identify the dominant yeast species associated with mango and rose apple fruit pulps in Cali, Colombia. A total of 90 isolates were obtained, which were grouped considering their colony morphology. The D1/D2 domain of the large ribosomal RNA gene (LSU rRNA gene) or internal transcribed spacer (ITS) 1, ribosomal gene 5.8S and ITS 2 (ITS) regions of one to several representative isolates from each group was sequenced and compared with type strains for identification. The species Hanseniaspora thailandica, H. opuntiae and Clavispora lusitaniae were reported as shared by both fruits, specific for rose apple (H. uvarum, Pichia terricola, Rhodosporidiobolus ruineniae and Candida albicans), or for Mango (Meyerozyma caribbica, M. guilliermondii, C. natalensis, Aureobasidium pullulans, Pichia sp., Saturnispora diversa and C. jaroonii). Two morphotypes were not identified at the taxonomic level of species and were reported as candidates for new species, belonging to the genera Wickerhamomyces and Pichia.

Microbiological characteristics of kumis, a traditional fermented Colombian milk, with particular emphasis on enterococci population.

Kumis is a traditional fermented cow milk produced and consumed in South West Colombia. The main objective of this research was to studied the enterococcal population, present in 13 kumis samples traditionally manufactured, for their role as beneficial organisms or opportunistic pathogens. The molecular identification of 72 isolates evidenced that Enterococcus faecalis and E. faecium were the dominant species. The genes gelE, esp, asa1, cyl and hyl, all associated with virulence factors in enterococci, were detected in 30 isolates, while 42 were free of virulence determinants. Skim milk media were fermented by all the different isolates and further tested for proteolysis (free NH(3) groups), Angiotensin-I Converting Enzyme (ACE) inhibitory activity and biogenic amines production. Nine E. faecalis and two E. faecium strains produced fermented milk with ACE-inhibitory activity values ranging from 39.7% to 84.35% .The digestion of fermented milk samples by pepsin and pancreatin evidenced an increase in ACE inhibitory activity, with E. faecalis KE09 as the best producer (IC50 = 14.25 µg ml(-1)). Moreover, the strains showed a very low tyrosine decarboxylase activity and did not produce histamine during 48 h fermentation in milk. This study underlines the that Colombian kumis is a good source of not virulent enterococci able to produce fermented milks with ACE-inhibitory activity.

Estandarización de un protocolo sencillo para la extracción de ADN genómico de levaduras / Standardising a simple protocol for extracting yeast from genomic DNA

Se estandarizó un protocolo rápido, sencillo y de bajo costo para la extracción de ADN genómico de levaduras a partir de lisis de la pared celular mediante tratamiento enzimático y precipitación por alcoholes. El empleo de la enzima Beta-glucoronidasa en reemplazo de la enzima Zimolasa, permitió obtener ADN en alta concentración (124,9±30,2 ng/λl) y de buena calidad (A260/A280 nm =1,86±0,1), ideal para su uso en estudios de biología molecular. Además, se adicionó un paso de incubación del ADN obtenido a 100° C para inactivar ADNasas. La calidad del ADN obtenido fue evaluada por medio de la amplificación de la región ITS1-5.8S-ITS2, presentando bandas definidas y cuantificables (entre 380 y 880 pb) ideales para estudios de identificación molecular y filogenia.

A quick, simple and low-cost protocol for extracting genomic DNA from yeast by cell wall lysis involving enzymatic treatment and alcoholic precipitation was standardised. Higher DNA yields (124.9±30.2 ng/λl) were obtained by using beta-glucuronidase instead of zymolyase; these had very high quality (A260/A280 nm = 1.86±0.1) and would be suitable for use in molecular biology assays. Moreover, a DNAse inactivation step was also introduced by incubation at 100 °C to further ensure DNA stability. DNA quality was assayed by PCR amplification of the ITS1-5.8S-ITS2 region, revealing defined, quantifiable 380 to 880 bp bands. These results show that the protocol is ideal for molecular identification and phylogenetic studies.

Detection and identification of wild yeasts in Champús, a fermented Colombian maize beverage.

The aim of this study was to identify and characterise the predominant yeasts in Champús, a traditional Colombian cereal-based beverage with a low alcoholic content. Samples of Champús from 20 production sites in the Cauca Valley region were analysed. A total of 235 yeast isolates were identified by conventional microbiological analyses and by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of ITS1-5.8S rDNA-ITS2. The dominant species were: Saccharomyces cerevisiae, Issatchenkia orientalis, Pichia fermentans, Pichia kluyveri var. kluyveri, Zygosaccharomyces fermentati, Torulospora delbruekii, Galactomyces geotrichum and Hanseniaspora spp. Model Champús systems were inoculated with single strains of some isolated sporogenus species and the aromatic profiles were analysed by SPME. Analysis of data showed that Champús strains produced high amounts of esters. The aromatic compounds produced by Saccharomyces and non-Saccharomyces yeasts from Champús can exert a relevant influence on the sensory characteristics of the fermented beverage. The Champús strains could thus represent an important source for new yeast biotypes with potential industrial applications.