Abstract

In this paper, we report an experimental result regarding the effects of audible sound on the growth of Escherichia coli (E. coli). Standardized E. coli suspensions of fixed concentration were used for inoculation throughout the experiment in nutrient agar (NA) and nutrient broth (NB). First, the samples were incubated at 37ºC for three hours in a water bath-shaker for NB and in a conventional oven for NA. The samples were then transferred to an acoustic chamber JedMark LV-1 with given sound treatment at controlled temperature of 24±2ºC for five hours for NB and 16 hours for NA. Three different tonal frequencies were selected for sound treatment in this experiment which is 1 kHz, 5 kHz and 15 kHz. The growth of E. coli was assessed by their cell number through indirect viable cell counts (E. coli on NA) and direct viable cell counts (E. coli on NB), after the incubation with sound in the acoustic chamber. We found that all selected frequencies were able to promote the growth of E. coli. In particular, the tonal sound of 5 kHz gave significant increase in cell number of E. coli for both growth media.

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