Aims
Kluyveromyces marxianus dairy strains were tested for γ‐aminobutyric acid (GABA) production. The genes involved in GABA catabolism (UGA1 and UGA2) and anabolism (GAD1) were found in K. marxianus ...genome. Their relative expression was evaluated with primer designed ad hoc.
Methods and Results
Strains were grouped on the basis of GAD1 gene sequence. Representative strains for each group were tested for GABA production by high‐performance liquid chromatography. All strains produced it at low levels. qRT‐PCR showed the absence of a relation between GABA production and GAD1 gene expression. UGA1 and UGA2 genes were not upregulated and low amounts of succinic acid were detected.
Conclusions
All strains released a low amount of GABA suggesting that probably it was stored within cells. The different behaviour of strains in terms of GABA and succinic acid production as well as gene expression highlighted the genetic and phenotypic biodiversity of this species.
Significance and Impact of the Study
GABA production and genes involved in its catabolism and anabolism were described in a population of dairy K. marxianus for the first time. The variability observed in terms of genetic and phenotypic biodiversity is important especially to exploit this non‐conventional yeast as microbial platform.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
► The possible factors influencing the occurence of amines in wines have been proposed. ► In Abruzzo wines tyramine, putrescine and histamine were found more abundant in red wines. ► The correlation ...resulting between putrescine and malic acid content was significant. ► Levels of histamine and tyramine in Abruzzo wines were below toxicity threshold.
Aim of this research was to study the effect of some agronomic and oenological factors on the content of biogenic amines as quality index of sixty-five Abruzzo wines. Sum of amines was found to be decreasing in the order: red (19.3±12.8mgL−1), rosé (9.20±6.34mgL−1), white (7.67±3.84mgL−1) wine. Significant differences in relationship among amines levels and chemical and chemico-physical characteristics of red, white and rosé wine are due to their different biotechnological process and winemaking. Besides the aging treatment, influential seems to be the effect of the winery, regardless of the area in which it is situated.
The single amines significantly correlated with their sum were putrescine, histamine and tyramine, even if reached levels were below toxicity threshold, demonstrating a good quality of the wines of Abruzzo whose consumption is no risk to the health of the consumer following the rules of proper nutrition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Aims
Flocculent wine yeasts were characterized for the expression of FLO1, FLO5, FLO8, AMN1 and RGA1 genes, growth kinetics and physicochemical properties of the cell surface during a 6‐month ...sparkling wine fermentation period.
Methods and Results
The expression of FLO1, FLO5, FLO8, AMN1 and RGA1 genes was determined by RT‐qPCR. The physicochemical characterization of yeast surface properties was evaluated by the microbial adhesion to solvents method. FLO5 gene was the most expressed one and a linear correlation with the flocculent degree was found. Flocculent strains were more hydrophobic than the commercial wine strain EC1118.
Conclusions
Gene expressions and the ability to face secondary wine fermentation conditions were strain dependent. The importance of FLO5 gene in developing the high flocculent characteristic of wine yeasts was highlighted. Cell surface properties depended on the time of fermentation.
Significance and Impact of the Study
Better knowledge about the expression of some genes encoding the flocculent phenotype which could be useful to select suitable starter cultures to improve sparkling wine technology was achieved. A step forward in understanding the complexity and strain‐specific nature of flocculation phenotype was done.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Lactobacillus pentosus is one of the few lactic acid bacteria (LAB) species capable of surviving in olive brine, and thus desirable during table olive fermentation. We have recently generated mutants ...of the efficient strain L. pentosus C11 by transposon mutagenesis and identified five mutants unable to survive and adapt to olive brine conditions. Since biofilm formation represents one of the main bacterial strategy to survive in stressful environments, in this study, the capacity of adhesion and formation of biofilm on olive skin was investigated for this strain and five derivative mutants which are interrupted in metabolic genes (enoA1 and gpi), and in genes of unknown function (“oba” genes). Confocal microscopy together with bacteria count revealed that the sessile state represented the prevailing L. pentosus C11 life-style during table olive fermentation. The characterization of cell surface properties showed that mutants present less hydrophobic and basic properties than the wild type (WT). In fact, their ability to adhere to both abiotic (polystyrene plates) and biotic (olive skin) surfaces was lower than that of the WT. Confocal microscopy revealed that mutants adhered sparsely to the olive skin instead of building a thin, multilayer biofilm. Moreover, RT-qPCR showed that the three genes enoA1, gpi and obaC were upregulated in the olive biofilm compared to the planktonic state. Thus enoA1, gpi and “oba” genes are necessary in L. pentosus to form an organized biofilm on the olive skin.
•L. pentosus C11 prevails in sessile state during olive fermentation.•Mutants were impaired in adhesion to abiotic and biotic surfaces.•oba, enoA1 and gpi genes are required for biofilm formation on the olive skin.•Olive surface is a biotic support for L. pentosus C11 adhesion and biofilm formation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
To evaluate some physiological characteristics of the Enterobacteriaceae isolated from Pecorino cheese. The production of organic acids, secondary volatile compounds, biogenic amines (BA) and the ...lipolytic and proteolytic activities of Citrobacter braakii, Enterobacter sakazakii, Escherichia coli, Kluyvera spp., Salmonella enterica ssp. arizonae and Serratia odorifera strains were determined in skim milk after 48 h of fermentation at 30°C. The proteolytic activity observed only in Ser. odorifera and Kluyvera spp. was confirmed by the peptide profiles of the pH 4·6-insoluble fraction using RP-HPLC; however, the lipase activity was evidenced in all the isolates of E. coli, Kluyvera spp. and Salm. enterica ssp. arizonae. During fermentation, all the strains utilized citric acid and produced significant quantities of putrescine followed by histamine, spermine and spermidine as well as acetic and lactic acid. Moreover, the major volatile compounds produced were ethanol, 2,3-butanedione, 3-hydroxy-2-butanone, 2-heptanone and acetone. The Enterobacteriaceae of dairy origin possess many metabolic activities that could affect the sensory quality of the cheese in which they grow during ripening. The important physiological characteristics possessed by Enterobacteriaceae confirm the complexity of the microbiota of Pecorino Abruzzese cheese, which influences the typical sensory properties of this product.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Enterococci, which represent a considerable part of the natural microbiota of Pecorino Abruzzese, were investigated for biochemical activities considered to have a potential role in cheese ripening. ...Acidifying activity was weak, while interesting differences were identified for proteolytic and peptidolytic capability, particularly on H-Lys-β-NA. The presence of C-4 esterase and C-8 esterase lipase, as well as enzymes such as phosphohydrolases and acid phosphatase was confirmed by means of API ZYM. SPME-GC analyses of volatile compounds revealed the production of ethanol, diacetyl and, of particular interest, acetoin after 15 days at 10
°C, with important differences among the species. After 15 days at 10
°C,
Enterococcus faecalis isolates were generally the most active, giving the highest results for most of the biochemical activities investigated, and also some
Enterococcus durans showed interesting metabolic features that might be important to the development of the peculiar sensory properties of this cheese.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The principal aim of this research was to evaluate the ability of different
Yarrowia lipolytica strains, having different origin, to grow in olive mill wastewater (OMW) and reduce its COD level. All ...the strains were able to grow in undiluted OMW; the comparison between the data obtained in a semi-synthetic medium and in OMW suggests that lipases with different specificity can be produced in relation to the medium composition.
Under the adopted conditions, the reduction of the OMW COD values varied from 1.47% and 41.22% of the initial value. Some strains determined a significant reduction of polyphenol content, while other ones caused its apparent increase. Moreover, some
Y. lipolytica strains, isolated from chilled foods, produced the highest citric acid concentrations. These results evidenced that some
Y. lipolytica strains are good candidates for the reduction of the pollution potential of OMW and for the production of enzymes and metabolites such as lipase and citric acid.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The aims of this work were to identify and characterize for some important technological properties the yeast species present throughout the ripening process of Pecorino Crotonese, a traditional ...cheese produced in a well defined area of Southern Italy. In particular, the strain technological properties considered include fermentation/assimilation of galactose and lactose, assimilation of lactate and citrate in the presence of different NaCl concentrations, hydrolysis of butter fat, skim milk, gelatine and casein, production of brown pigments in cheese agar and ability to produce biogenic amines. High yeast levels were recorded in cheese samples already after 5
h of brining (about 5
log
cfu/g) and these concentration remained constant during ripening. The yeast isolates belonged to restrict number of yeast species. While
Kluyveromyces lactis and
Saccharomyces cerevisiae were isolated prevalently in the first stages of Pecorino Crotonese production,
Yarrowia lipolytica and
Debaryomyces hansenii dominated during the later stages of maturation. Otherwise, the latter two were very NaCl resistant species. In fact,
D. hansenii strains conserved the ability to assimilate lactose and galactose in the presence of 10% NaCl, while almost all the strains of
Y. lipolytica isolated assimilated citrate and lactate up to 7.5% NaCl.
Y. lipolytica isolates evidenced also the highest proteolytic and lipolytic activities and the capability to catabolize tyrosine producing brown pigment. In addition they resulted in the highest aminobiogenic potential decarboxylating ornithine, phenylalanine, tyrosine and lysine. However, they were not able to produce histamine, biogenic amine produced by three strains of
D. hansenii.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In the year 2012, 288 raw milk samples were collected from six different dairy cow farms and analyzed for the presence of aflatoxin M, (AFM,) using the ELISA technique. The AFM, levels ranged from 5 ...to 25 ng/kg and the highest concentrations were found in autumn, with a significant difference (p<0.05) between February and November. The EU legal limit of 50 ng/kg has never been exceeded. Even if the results of the present study show a low risk for AFM,, its occurrence in dairy products has to be regularly monitored due to their importance as foodstuffs for people and children above all.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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