Abstract
This study examines the in vitro effect of Quillaja saponaria extracts on Asaia spp. planktonic cells and biofilms, in comparison and combination with two disinfectants: peracetic acid and N-ethyl-N,N-dimethylhexadecylammonium bromide. The growth of six bacterial strains was evaluated spectrophotometrically. Biofilm eradication was determined using the plate count method and luminometry. The planktonic cells were characterized by relatively high resistance to peracetic acid and higher sensitivity to N-ethylo-N,N-dimethylohexadecylioamonium bromide. In almost all the tested strains, growth was inhibited by 0.125% (v/v) peracetic acid and 0.0313% (w/v) quaternary ammonium compound. However, combinations of cell pretreatment using saponin and peracetic acid action were the most efficient against both planktonic and biofilm cells. The minimum inhibitory concentrations for peracetic acid were 4–8 times lower than those for bacterial strains without preliminary saponin action. Eradication of Asaia spp. biofilms reduced the number of living cells by 4–5 logarithmic units. These results demonstrate the synergetic action of saponin extract and disinfectant, and could be useful in the development of industrial strategies against Asaia spp. biofilms.
Highlights
Since Moore et al first detected the presence of Asaia spp. in fruit-flavored bottled water in 2002, it has become recognized as a common bacterial spoilage in the beverage industry
Minimal Inhibitory Concentration (MIC) was used as a comparative measure of the effectiveness of two different disinfectants: N-ethyl-N,N-dimethylhexadecylammonium bromide (QAC) and peracetic acid (PAA) against Asaia spp
The bacteria were characterized by similar sensitivity to QAC, but differentiation was noticeably more pronounced in the case of sensitivity to PAA
Summary
Since Moore et al first detected the presence of Asaia spp. in fruit-flavored bottled water in 2002, it has become recognized as a common bacterial spoilage in the beverage industry. It is difficult to determine the origin of Asaia spp. contamination in soft drinks. Asaia spp. have been isolated from grapes grown in South. Australian vineyards and from insects native to tropical climates [5,6]. These bacteria exhibit unique adaptive abilities [7]. In the soft drinks environment, Asaia spp. are able to grow at pH 3.45, in the presence of sorbate, benzoate, and dimethyldicarbonate at concentrations of 1.5 mmol/L and higher [2]
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