Bifacial biological effects of ethanol: acetaldehyde production by oral Streptococcus species and the antibacterial effects of ethanol against these bacteria

Figures & data

Figure 1. Population doubling times and growth curves of oral Streptococcus species in the presence of ethanol

A. Growth curves of oral Streptococcus species in the presence of ethanol.Bars, standard deviation; n = 3.B. Doubling times of oral Streptococcus species in the presence of ethanol.Bars, standard deviation; ▲, A doubling time of > 3.5 hours was considered to be indicative of no growth. *p < 0.05, **p < 0.01; n = 3.

Figure 2. Bacterial viability (CFU) after exposure to 5,000 or 10,000 mM of ethanol

Bars, standard deviation; **p < 0.01; n = 3.

Figure 3. Acetaldehyde production from ethanol by oral Streptococcus species

Bars, standard deviation; *p < 0.05, **p < 0.01; n = 3.

Table 1. Maximum acetaldehyde production (V_max) and the concentration of ethanol at which the production was half of the maximum acetaldehyde production (C_1/2)

	S. mitis	S. mutans	S. salivarius	S. gordonii	S. sanguinis
The maximum acetaldehyde production (Vmax) (μmol/mg of wet weight of cells・min)	72.1 ± 12.7 ^a, b, c	25.7 ± 3.5 ^a, d	68.8 ± 11.8 ^d, e	41.1 ± 14.8 ^b	19.2 ± 8.1 ^c, e
The concentration of ethanol at the maximum acetaldehyde production (mM)	2,000	2,000	2,000	2,000	2,000
The concentration of ethanol at which the production was half of the maximum acetaldehyde production (C1/2) (mM)	38.8 ± 15.4 ^f	478.5 ± 70.0	488.2 ± 160.6	605.0 ± 316.4	964.5 ± 408.8 ^f

a – e; significant differences between two bacterial species; e.g. ‘a’ shows that there is a significant differences between S. mitis and S. mutans.

a, c, d, e and f; p < 0.01, b; p < 0.05.

Figure 4. Bifacial biological effects of ethanol

Ethanol functions as both a metabolic substrate for bacterial acetaldehyde production and an antibacterial agent. The maximum acetaldehyde production was seen at an ethanol concentration of about 2,000 mM. The growth of oral streptococcal species was inhibited by ≥ 1,000 mM of ethanol, and these species became non-viable at ethanol concentrations of 5,000 to 10,000 mM; however, acetaldehyde production by these species peaked at an ethanol concentration of 2,000 mM and was still seen at an ethanol concentration of 10,000 mM.