Chemical Constitution and Antimicrobial Activity of Kefir Fermented Beverage

Abstract

Kefir beverage (KB) is a fermented milk initiated by kefir grains rich with starter probiotics. The KB produced in this study seemed to contain many chemical compounds elucidated by gas chromatography–mass spectrometry (GC-MS) and IR spectra. These compounds could be classified into different chemical groups such as alcohols, phenols, esters, fatty esters, unsaturated fatty esters, steroids, polyalkenes, heterocyclic compounds and aromatic aldehydes. Both KB and neutralized kefir beverage (NKB) inhibited some pathogenic bacteria including Escherichia coli ATCC11229 (E. coli), Listeria monocytogenes ATCC 4957 (L. monocytogenes), Bacillus cereus ATCC 14579 (B. cereus), Salmonella typhimurium ATCC 14028 (Sal. typhimurium) as well as some tested fungal strains such as Aspergillus flavus ATCC 16872 (A. flavus) and Aspergillus niger ATCC 20611 (A. niger), but the inhibitory activity of KB was more powerful than that obtained by NKB. It also appeared to contain four lactic acid bacteria species, one acetic acid bacterium and two yeast species. Finally, the KB inhibited distinctively both S. aureus and Sal. typhimurium bacteria in a brain heart infusion broth and in some Egyptian fruit juices, including those made with apples, guava, strawberries and tomatoes.

Antibacterial Peptides Produced by Alcalase from Cowpea Seed Proteins

“…Concerning the bioactive components within the investigated AMPs, the positive ions portion include non-polar hydrophobic amino acids in 9 out of 11 residues investigated, such as Cys am-Trp, Cys am-Trp, Trp-Ser, His-Cys am, Trp-Met-Arg (penta-peptide), Trp-Cys am (2 residues), Leu-Ala, Asn-Val and Arg-Gly, which were known to attach the negatively charged phospholipid of bacterial cell membranes; making electrostatic forces which could make pores within bacterial cell membranes; from which cell electrolytes can emerges outside bacterial cells [15,22]. Also, the residues containing Sulphur, such as met within the pentapeptide and cysteine showed to be of distinctive antimicrobial activity [52]. The bioactive components within the amino acids of the negative ions portion contained tryptophane within 4 residues out of 5 residues detected and showed to be bioactive components, as shown above, for the positive ions of fraction [41].…”

“…Moreover, the releasing of peptides with a smaller molecular mass by alcalase is of more mobility and inhibitory activity than the ones with high molecular weight [53]. In addition, the Arg-Cys am residue showed previouslya distinctive bioactivity against bac-teria since the amino group of arginine could accept the proton-giving, positively-charged NH3 + group, which could attach with the negatively-charged bacterial cell membrane, giving bacterial death [52].…”

Chemical Constitution and Antimicrobial Activity of Kombucha Fermented Beverage

“…The esters and fatty acid esters detected herein were, in general, positively charged and more hydrophobic; such hydrophobicity allows electrostatic interactions with the bacterial cellular components, resulting in loss of cell viability via formation of fully deorganized killed cells. They also act as antibacterial food additives through the inhibition of bacterial growth and biofilm formation [ 10 , 31 ].…”

“…Probiotics are live microorganisms that when administered in adequate amounts, improve many nutritional and digestive functions [ 1 , 2 ]. After a long history of safe use of probiotics in fermented food products and an increased recognition of their beneficial human health effects, in addition to their significant potential use as therapeutic options for a variety of diseases, the food industry has become increasingly interested in these types of microorganisms [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The mechanisms underlying the beneficial effects of probiotics are likely to be multifactorial.…”

“…The most widely used probiotics to date are several genera of both lactic and acetic acid bacteria as well as yeasts; they are applied in many functional foods and dietary supplements [ 1 ]. Furthermore, probiotics have been reported to display a protective role by direct competing with intestinal pathogens through the release of antibacterial substances such as bacteriocins that could kill the multidrug resistant bacteria [ 4 , 11 , 12 , 13 ] or metabolites such as acetic acid and lactic acid [ 1 , 10 ]. Probiotic yeasts such as Saccharomyces cerevisiae and S. boulardii have also been demonstrated to confer health benefits [ 14 , 15 ].…”