Sound Stimulation Can Affect Saccharomyces cerevisiae Growth and Production of Volatile Metabolites in Liquid Medium

The biological effect of sound on microorganisms has been a field of interest for many years, with studies mostly focusing on ultrasonic and infrasonic vibrations. In the audible range (20 Hz to 20 kHz), sound has been shown to both increase colony formation and disrupt microbial growth, depending upon the organism and frequency of sound used. In the brewer's yeast Saccharomyces cerevisiae, sound has been shown to significantly alter growth, increase alcohol production, and affect the metabolite profile. In this study, S. cerevisiae was exposed to a continuous 90 dB @ 20 μPa tone at different frequencies (0.1 kHz, 10 kHz, and silence). Fermentation characteristics were monitored over a 50-h fermentation in liquid malt extract, with a focus on growth rate and biomass yield. The profile of volatile metabolites at the subsequent stationary phase of the ferment was characterised by headspace gas chromatography-mass spectrometry. Sound treatments resulted in a 23% increase in growth rate compared to that of silence. Subsequent analysis showed significant differences in the volatilomes between all experimental conditions. Specifically, aroma compounds associated with citrus notes were upregulated with the application of sound. Furthermore, there was a pronounced difference in the metabolites produced in high- versus low-frequency sounds. This suggests industrial processes, such as beer brewing, could be modulated by the application of audible sound at specific frequencies during growth.

Effect of Heat and Sonic Vibration on Penetration of a Flowable Resin Composite Used as a Pit and Fissure Sealant

OBJECTIVE

To evaluate penetration of a flowable resin composite into fissures using three different application methods: (1) conventional, (2) heat, and (3) sonic vibration.

STUDY DESIGN

Forty-five sound maxillary third molars were divided randomly into three groups (n=15 per group). The occlusal surfaces of the teeth were etched and flowable resin composites were applied into the fissure using the assigned application method. The crowns were sectioned and examined with an optical microscope to assess penetration. In addition, three-point flexural strength was analyzed.

RESULTS

The sonic vibration group exhibited significantly greater penetration into the fissure compared with the other test groups (p<0.001). The heat group exhibited greater penetration into the fissure compared with the conventional group (p=0.003). However, three-point flexural strength was similar among all groups (p>0.05).

CONCLUSIONS

Sonic vibration and heat increased penetration into fissures. Notably, sonic vibration exhibited the greatest penetration. We found that the application method did not influence the three-point flexural strength.

Enhancing proliferation and ECM expression of human ACL fibroblasts by sonic vibration

Effects of mechanical vibration on cell activity and behavior remain controversial: There has been evidence on both positive and negative effects. Furthermore, research on the anterior cruciate ligament (ACL) has as yet been limited and the frequency-related effects remain unknown, even though ACL injury is common and an injured ACL hardly spontaneously recovers. The object of this work was to address the influence of mechanical vibration on ACL fibroblasts, to determine the effects of frequencies, and to further study this effect at the cellular level. We found that sonic vibration affected ACL fibroblasts' proliferation and metabolism in a frequency-dependent manner, and 20 Hz gave rise to the most ACL cell activity and comprehensively increased extracellular matrix (ECM) contents, including collagen type I, collagen type III, fibronectin, elastin, tenascin, glycosaminoglycan (GAG), and the cytoskeleton protein vimentin. Thus, our results indicate that sonic vibration possesses frequency-dependent effects on proliferation and productivity of ACL fibroblast with an optimal frequency of 20 Hz under the present stimulation conditions, providing further information for future research in how vibrational stimulation manipulates ACL cellular behavior.