Enhanced growth of lactobacilli and bioconversion of isoflavones in biotin-supplemented soymilk upon ultrasound-treatment

Effects of ultrasound on the fermentation profile of fermented milk products incorporated with lactic acid bacteria

“…The micro-bubbles create micro-streaming and/or liquid jets (Maciulevičius et al, 2016), which generate a strong shear force that breaks the chemical bonds in the cell membranes (Tabatabaie & Mortazavi, 2008) (Gao, Hemar, Ashokkumar, Paturel, & Lewis, 2014a;Gao, Lewis, Ashokkumar, & Hemar, 2014b), which play a vital role in lipid bilayer relocation and membrane disruption through lipid peroxidation. Furthermore, it was also revealed that peroxidation of membrane lipids (Ewe et al, 2012;Lentacker et al, 2014) and conformational unfolding of proteins that are located on the surface of the cell membrane increase membrane fluidity and membrane permeabilisation upon US treatment (Ewe et al, 2012). From the available literature, it is clear that a low level of sonoporation can be used to improve the permeability of cell membranes, resulting in improved mass transfer of substrates across the microbial cell membrane and efficient removal of by-products of cellular metabolism, which eventually improves microbial growth (Ojha et al, 2017).…”

“…Moreover, flow cytometric analysis revealed that US increased both membrane permeability and fluidity of LAB (Ewe et al, 2012). These changes may result from emulsification of cell membrane lipids (lipid peroxidation) due to intracellular cavitation or associated air bubbles.…”

“…Consequently, authors suggested that ultrasonic waves promoted the fermentation process under conditions where cavitation was not generated, and was suppressed when cavitation occurred. However, the influence of factors such as different milk composition, (Ewe, Abdullah, Bhat, Karim, & Liong, 2012;Nguyen et al, 2009;Wang & Sakakibara, 1997;Wu et al, 2001). Another mechanism, proposed by Shimada et al (2004) and Piyasena, Mohareb, and McKellar (2003), is that a slight local temperature rise due to the heat derived from ultrasonic absorption may activate the lactic bacteria and shorten the fermentation time.…”

“…Using microscopy, the effect of power US (20 kHz, 30 min) on cell wall permeability of lactic acid bacteria has been investigated by several researchers (Cameron, McMaster, & Britz, 2008;Shershenkov & Suchkova, 2015;Tabatabaie & Mortazavi, 2008). LAB that were exposed to US treatment showed both pore formation and cellular damage (Ewe et al, 2012). Three types of micro-damage, namely micro-cracks, micro-voids and ruptures, have been identified in cell membranes of LAB (Tabatabaie & Mortazavi, 2008).…”

“…Therefore, it can be suggested that the coagulation time of milk is shortened by US as pore formation in bacterial cell membranes increases cell membrane permeabilisation and enhances the cellular transport of metabolites. However, it was observed that the changes associated with the bacterial cell membrane were more prominent with increasing treatment amplitudes and treatment durations (Ewe et al, 2012). Therefore, the optimum conditions for such ultrasonication parameters should be carefully determined before applying sonication to the fermented dairy products.…”