Livio Antonielli

Lactic Acid Bacterium and Yeast Microbiotas of 19 Sourdoughs Used for Traditional/Typical Italian Breads: Interactions between Ingredients and Microbial Species Diversity

ABSTRACT The study of the microbiotas of 19 Italian sourdoughs used for the manufacture of traditional/typical breads allowed the identification, through a culture-dependent approach, of 20 and 4 species of lactic acid bacteria (LAB) and yeasts, respectively. Numerically, the most frequent LAB isolates were Lactobacillus sanfranciscensis (ca. 28% of the total LAB isolates), Lactobacillus plantarum (ca. 16%), and Lactobacillus paralimentarius (ca. 14%). Saccharomyces cerevisiae was identified in 16 sourdoughs. Candida humilis, Kazachstania barnettii, and Kazachstania exigua were also identified. As shown by principal component analysis (PCA), a correlation was found between the ingredients, especially the type of flour, the microbial community, and the biochemical features of sourdoughs. Triticum durum flours were characterized by the high level of maltose, glucose, fructose, and free amino acids (FAA) correlated with the sole or main presence of obligately heterofermentative LAB, the lowest number of facultatively heterofermentative strains, and the low cell density of yeasts in the mature sourdoughs. This study highlighted, through a comprehensive and comparative approach, the dominant microbiotas of 19 Italian sourdoughs, which determined some of the peculiarities of the resulting traditional/typical Italian breads.

Taxonomic structure of the yeasts and lactic acid bacteria microbiota of pineapple (Ananas comosus L. Merr.) and use of autochthonous starters for minimally processing

Pichia guilliermondii was the only identified yeast in pineapple fruits. Lactobacillus plantarum and Lactobacillus rossiae were the main identified species of lactic acid bacteria. Typing of lactic acid bacteria differentiated isolates depending on the layers. L. plantarum 1OR12 and L. rossiae 2MR10 were selected within the lactic acid bacteria isolates based on the kinetics of growth and acidification. Five technological options, including minimal processing, were considered for pineapple: heating at 72 degrees C for 15 s (HP); spontaneous fermentation without (FP) or followed by heating (FHP), and fermentation by selected autochthonous L. plantarum 1OR12 and L. rossiae 2MR10 without (SP) or preceded by heating (HSP). After 30 days of storage at 4 degrees C, HSP and SP had a number of lactic acid bacteria 1000 to 1,000,000 times higher than the other processed pineapples. The number of yeasts was the lowest in HSP and SP. The Community Level Catabolic Profiles of processed pineapples indirectly confirmed the capacity of autochthonous starters to dominate during fermentation. HSP and SP also showed the highest antioxidant activity and firmness, the better preservation of the natural colours and were preferred for odour and overall acceptability.

Yamadazyma terventina sp. nov., a yeast species of the Yamadazyma clade from Italian olive oils

During an investigation of olive oil microbiota, three yeast strains were found to be divergent from currently classified yeast species according to the sequences of the D1/D2 domain of the gene encoding the rRNA large subunit (LSU) and the internal transcribed spacer region including the gene for 5.8S rRNA. Phylogenetic analysis revealed that these strains, designated CBS 12509, CBS 12510(T) and CBS 12511, represent a novel anascosporogenous species described herein as Yamadazyma terventina sp. nov; the type strain is DAPES 1924(T) (= CBS 12510(T) = NCAIM Y.02028(T)). This novel species was placed in the Yamadazyma clade, with Yamadazyma scolyti, Candida conglobata and Candida aaseri as closest relatives. Y. terventina differs from the above-mentioned species in the ability to strongly assimilate dl-lactate and weakly assimilate ethanol.

Effect of pH on potassium metabisulphite biocidic activity against yeast and human cell cultures

Potassium metabisulphite (PMB) is a common antimicrobial additive in the food industry. In aqueous solutions, PMB leads to complex equilibria according to its concentration, pH and temperature, and different chemical species can be present. In winemaking, PMB is used at low pH, suggesting that the biocidic activity is exerted by sulphur dioxide while, in other applications, it is employed at higher pH values with little if any dissociation. This observation leads to the question of which chemical form is biologically active. For this reason, Saccharomyces cerevisiae cells were subjected to PMB solutions at different pH values and analysed with a Fourier transform infrared spectroscopy (FTIR)-based bioassay, to assess the entity and the type of stress. Cell viability was determined and compared to the metabolomics (FTIR) stress indices, which revealed that the metabolomics fingerprint was an effective description of the cell health state. GC-MS metabolite profiles were obtained to describe (in detail) the changes caused by PMB in the fatty acids region. Human dermal fibroblasts (HDF) were also subjected to PMB stress at pH 7.0 and analysed with the FTIR protocol, in order to compare the response spectra of yeast and human cell cultures.

Centrality of Objects in a Multidimensional Space and its Effects on Distance-Based Biological Classifications

Typology is based on the concept that one individual (the type) can represent the whole group. In yeast taxonomy the type strain is the representative of the whole species and is considered an important tool for classification. Although the evolutionary, phylogenetic and biological species concepts are in contrast with this approach, the International Codes of nomenclature still use typology, which remains one of the most operative systems. These incongruities demand a multidisciplinary investigation on the nature of the type, its characteristics and the possibility of the type to be defined on the basis of a shareable criterion. In this paper we present an approach to the problem of type centrality based on mathematical demonstrations and numerical examples. This paper intended to show the possibilities offered to bioinformatics research by the implementation of multidisciplinary approaches in biology and in proposing a general approach to the definition of the type representing any sort of set, described with multiple descriptors.

Candida coquimbonensis sp. nov., a link between Australian and Nearctic/Neotropical Phaffomyces.

A novel species of ascomycetous yeast, Candida coquimbonensis sp. nov., from the necrotic tissue of cacti in Chile and Australia is described. C. coquimbonensis sp. nov. is closely related and phenotypically similar to Phaffomyces opuntiae. There is no overlap in the geographical distribution between C. coquimbonensis and any species in the Phaffomyces clade. However, this is the first member of the clade to be collected in both native (Chile) and non-native (Australia) cactus habitats. The type strain of C. coquimbonensis sp. nov. is TSU 00-206.4B(T) ( = CBS 12348(T) = USCFST 12-103(T)).

A Multidisciplinary Approach to the Microbial Species Concept: The Role of Bioinformatics in the Search of Detectable Discontinuities

The problem of species and in particular microbial species is central in biology. An active collaboration of various specialists such as taxonomists, epistemologists, mathematicians and bioinformatics experts is desirable for its solution. This article intended to show the possibilities and perspectives of bioinformatics research in understanding the ontological problem of species, i.e. the problem of the existence of the microbial species. The approach undertaken of this paper is based on the concept that if microbial species exist, then there should be detectable discontinuities or disconnections between microorganisms assigned to different species. A yeast model has been used to show how the distances from a reference organism raise with the increase of the number of different strains included in the study.