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Tracking adulteration of nectar honey varieties using a high-resolution melting qPCR technique validated with melissopalinology
Multiple region high resolution melting-based method for accurate differentiation of food-derived yeasts at species level resolution
Acetic and citric acids effect the type II secretion system and decrease the metabolic activities of salmon spoilage-related Rahnella aquatilis KM05
AbstractRahnella aquatilis causes seafoods to spoil by metabolizing sulfur-containing amino acids and/or proteins, producing H2S in products. The type II secretion system (T2SS) regulates the transport of proteases from the cytoplasm to the surrounding environment and promotes bacterial growth at low temperatures. To prevent premature fish spoilage, new solutions for inhibiting the T2SS of bacteria should be researched. In this study, global transcriptome sequencing was used to analyze the spoilage properties of R. aquatilis KM05. Two of the mapped genes/coding sequences (CDSs) were matched to the T2SS, namely, qspF and gspE, and four of the genes/CDSs, namely, ftsH, rseP, ptrA and pepN, were matched to metalloproteases or peptidases in R. aquatilis KM05. Subinhibitory concentrations of citric (18 µM) and acetic (41 µM) acids caused downregulation of T2SS-related genes (range from − 1.0 to -4.5) and genes involved in the proteolytic activities of bacteria (range from − 0.5 to -4.0). The proteolytic activities of R. aquatilis KM05 in vitro were reduced by an average of 40%. The in situ experiments showed the antimicrobial properties of citric and acetic acids against R. aquatilis KM05; the addition of an acidulant to salmon fillets limited microbial growth. Citric and acetic acids extend the shelf life of fish-based products and prevent food waste.
Dobór i walidacja genów referencyjnych do różnicowej analizy ekspresji genów u Yarrowia lipolytica
High-Resolution Melting Analysis Potential for Saccharomyces cerevisiae var. boulardii Authentication in Probiotic-Enriched Food Matrices
To date, the only probiotic yeast with evidence of health-promoting effects is Saccharomyces cerevisiae var. boulardii. The expanded market including dietary supplements and functional foods supplemented with Saccharomyces cerevisiae var. boulardii creates an environment conductive to food adulterations, necessitating rapid testing to verify product probiotic status. Herein, qPCR-HRM analysis was tested for probiotic yeast identification. The effectiveness of the primer pairs’ set was examined, designed to amplify heterogeneous regions in (a) rDNA sequences previously designed to identify food-derived yeast and (b) genes associated with physiological and genotypic divergence of Saccharomyces cerevisiae var. boulardii. Preliminary tests of amplicons’ differentiation power enabled the selection of interspecies sequences for 18SrRNA and ITS and genus-specific sequences HO, RPB2, HXT9 and MAL11. The multi-fragment qPCR-HRM analysis was sufficient for culture-dependent Saccharomyces cerevisiae var. boulardii identification and proved effective in the authentication of dietary supplements’ probiotic composition. The identification of S. cerevisiae var. boulardii in complex microbial mixtures of kefir succeeded with more specific intragenus sequences HO and RPB2. The predominance of S. cerevisiae var. boulardii in the tested matrices, quantitatively corresponded to the probiotic-enriched food, was crucial for identification with qPCR–HRM analysis. Considering the reported assumptions, qPCR-HRM analysis is an appropriate tool for verifying probiotic-enriched food.