Limits...
Effects of sub-lethal high-pressure homogenization treatment on the outermost cellular structures and the volatile-molecule profiles of two strains of probiotic lactobacilli.

Tabanelli G, Vernocchi P, Patrignani F, Del Chierico F, Putignani L, Vinderola G, Reinheimer JA, Gardini F, Lanciotti R - Front Microbiol (2015)

Bottom Line: Moreover, the effect of HPH treatment on the metabolism of probiotic cells within a dairy product during its refrigerated storage was investigated using SPME-GC-MS.The results of this study will contribute to understanding the changes that occur in the outermost cellular structures and the metabolism of LAB in response to HPH treatment.The findings of this investigation may contribute to elucidating the relationships between these changes and the alterations of the technological and functional properties of LAB induced by pressure treatment.

View Article: PubMed Central - PubMed

Affiliation: Centro Interdipartimentale di Ricerca Industriale Agroalimentare, Università degli Studi di Bologna Cesena, Italy.

ABSTRACT
Applying sub-lethal levels of high-pressure homogenization (HPH) to lactic acid bacteria has been proposed as a method of enhancing some of their functional properties. Because the principal targets of HPH are the cell-surface structures, the aim of this study was to examine the effect of sub-lethal HPH treatment on the outermost cellular structures and the proteomic profiles of two known probiotic bacterial strains. Moreover, the effect of HPH treatment on the metabolism of probiotic cells within a dairy product during its refrigerated storage was investigated using SPME-GC-MS. Transmission electron microscopy was used to examine the microstructural changes in the outermost cellular structures due to HPH treatment. These alterations may be involved in the changes in some of the technological and functional properties of the strains that were observed after pressure treatment. Moreover, the proteomic profiles of the probiotic strains treated with HPH and incubated at 37°C for various periods showed different peptide patterns compared with those of the untreated cells. In addition, there were differences in the peaks that were observed in the low-mass spectral region (2000-3000 Da) of the spectral profiles of the control and treated samples. Due to pressure treatment, the volatile-molecule profiles of buttermilk inoculated with treated or control cells and stored at 4°C for 30 days exhibited overall changes in the aroma profile and in the production of molecules that improved its sensory profile, although the two different species imparted specific fingerprints to the product. The results of this study will contribute to understanding the changes that occur in the outermost cellular structures and the metabolism of LAB in response to HPH treatment. The findings of this investigation may contribute to elucidating the relationships between these changes and the alterations of the technological and functional properties of LAB induced by pressure treatment.

No MeSH data available.


Related in: MedlinePlus

Transmission electron micrographs of Lactobacillus paracasei A13: control cells (0.1 MPa) (A,B); 50 MPa HPH treated cells (C,D). Magnification: 28,500x (A) 73,000x (B) and 52,000x (C,D).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585067&req=5

Figure 1: Transmission electron micrographs of Lactobacillus paracasei A13: control cells (0.1 MPa) (A,B); 50 MPa HPH treated cells (C,D). Magnification: 28,500x (A) 73,000x (B) and 52,000x (C,D).

Mentions: Figures 1, 2 show TEM images of treated and untreated L. paracasei A13 and L. acidophilus DRU cells. As shown in Figures 1A,B, cell-wall and inner-membrane structures were clearly visible in the control (0.1 MPa) cells of L. paracasei A13, as it was an external capsule of proteinaceous material surrounding the cell wall. TEM images of cells of the same strain after HPH treatment at 50 MPa (Figures 1C,D) showed changes in the structures of 70–80% of the cells. The external capsule of proteinaceous material surrounding the wall of non-treated L. paracasei A13 cells was no longer visible after HPH treatment and the cell surface appeared jagged (indicated using an arrow in Figure 1C). Moreover, the cytoplasm appeared to be compressed and it was detached from the outermost cellular structures (indicated using an arrow in Figure 1D). The effects of pressure treatment on the outermost cellular structures were also visible in the TEM images of L. acidophilus, a species that is characterized by the presence of an S-layer surrounding the cell wall. As shown in Figures 2A,B, a continuous, thin, electron-dense layer was visible at the outer edge of the walls of the L. acidophilus DRU control cells, whereas this layer appeared discontinuous in the pressure-treated cells (Figures 2C,D; indicated using arrows). The HPH-treatment induced morphological changes observed in the TEM images did not significantly impaired cell viability, as demonstrated by cell counts obtained after HPH treatment. However, these morphological changes could be related to changes in some of the technological and functional properties of the strains observed after pressure treatment that were reported by Tabanelli et al. (2012, 2013).


Effects of sub-lethal high-pressure homogenization treatment on the outermost cellular structures and the volatile-molecule profiles of two strains of probiotic lactobacilli.

Tabanelli G, Vernocchi P, Patrignani F, Del Chierico F, Putignani L, Vinderola G, Reinheimer JA, Gardini F, Lanciotti R - Front Microbiol (2015)

Transmission electron micrographs of Lactobacillus paracasei A13: control cells (0.1 MPa) (A,B); 50 MPa HPH treated cells (C,D). Magnification: 28,500x (A) 73,000x (B) and 52,000x (C,D).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585067&req=5

Figure 1: Transmission electron micrographs of Lactobacillus paracasei A13: control cells (0.1 MPa) (A,B); 50 MPa HPH treated cells (C,D). Magnification: 28,500x (A) 73,000x (B) and 52,000x (C,D).
Mentions: Figures 1, 2 show TEM images of treated and untreated L. paracasei A13 and L. acidophilus DRU cells. As shown in Figures 1A,B, cell-wall and inner-membrane structures were clearly visible in the control (0.1 MPa) cells of L. paracasei A13, as it was an external capsule of proteinaceous material surrounding the cell wall. TEM images of cells of the same strain after HPH treatment at 50 MPa (Figures 1C,D) showed changes in the structures of 70–80% of the cells. The external capsule of proteinaceous material surrounding the wall of non-treated L. paracasei A13 cells was no longer visible after HPH treatment and the cell surface appeared jagged (indicated using an arrow in Figure 1C). Moreover, the cytoplasm appeared to be compressed and it was detached from the outermost cellular structures (indicated using an arrow in Figure 1D). The effects of pressure treatment on the outermost cellular structures were also visible in the TEM images of L. acidophilus, a species that is characterized by the presence of an S-layer surrounding the cell wall. As shown in Figures 2A,B, a continuous, thin, electron-dense layer was visible at the outer edge of the walls of the L. acidophilus DRU control cells, whereas this layer appeared discontinuous in the pressure-treated cells (Figures 2C,D; indicated using arrows). The HPH-treatment induced morphological changes observed in the TEM images did not significantly impaired cell viability, as demonstrated by cell counts obtained after HPH treatment. However, these morphological changes could be related to changes in some of the technological and functional properties of the strains observed after pressure treatment that were reported by Tabanelli et al. (2012, 2013).

Bottom Line: Moreover, the effect of HPH treatment on the metabolism of probiotic cells within a dairy product during its refrigerated storage was investigated using SPME-GC-MS.The results of this study will contribute to understanding the changes that occur in the outermost cellular structures and the metabolism of LAB in response to HPH treatment.The findings of this investigation may contribute to elucidating the relationships between these changes and the alterations of the technological and functional properties of LAB induced by pressure treatment.

View Article: PubMed Central - PubMed

Affiliation: Centro Interdipartimentale di Ricerca Industriale Agroalimentare, Università degli Studi di Bologna Cesena, Italy.

ABSTRACT
Applying sub-lethal levels of high-pressure homogenization (HPH) to lactic acid bacteria has been proposed as a method of enhancing some of their functional properties. Because the principal targets of HPH are the cell-surface structures, the aim of this study was to examine the effect of sub-lethal HPH treatment on the outermost cellular structures and the proteomic profiles of two known probiotic bacterial strains. Moreover, the effect of HPH treatment on the metabolism of probiotic cells within a dairy product during its refrigerated storage was investigated using SPME-GC-MS. Transmission electron microscopy was used to examine the microstructural changes in the outermost cellular structures due to HPH treatment. These alterations may be involved in the changes in some of the technological and functional properties of the strains that were observed after pressure treatment. Moreover, the proteomic profiles of the probiotic strains treated with HPH and incubated at 37°C for various periods showed different peptide patterns compared with those of the untreated cells. In addition, there were differences in the peaks that were observed in the low-mass spectral region (2000-3000 Da) of the spectral profiles of the control and treated samples. Due to pressure treatment, the volatile-molecule profiles of buttermilk inoculated with treated or control cells and stored at 4°C for 30 days exhibited overall changes in the aroma profile and in the production of molecules that improved its sensory profile, although the two different species imparted specific fingerprints to the product. The results of this study will contribute to understanding the changes that occur in the outermost cellular structures and the metabolism of LAB in response to HPH treatment. The findings of this investigation may contribute to elucidating the relationships between these changes and the alterations of the technological and functional properties of LAB induced by pressure treatment.

No MeSH data available.


Related in: MedlinePlus