J. Microbiol. Biotechnol. (2012), 22(0), 000–000 http://dx.doi.org/10.4014/jmb.1201.12073 First published online March 21, 2012 pISSN 1017-7825 eISSN 1738-8872 Growth Properties and Cholesterol Removal Ability of Electroporated Lactobacillus acidophilus BT 1088 Lye, H. S. 1 , B. Y. Khoo 2 , A. A. Karim 1 , G. Rusul 1 , and M. T. Liong 1 * 1 School of Industrial Technology, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia 2 Institute for Research in Molecular Medicine, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia Received: January 2, 2012 / Revised: February 3, 2012 / Accepted: February 6, 2012 This study aimed to evaluate the effects of electroporation on the cell growth, cholesterol removal, and adherence abilities of L. acidophilus BT 1088 and their subsequent passages. The growth of electroporated parent cells increased (P<0.05) by 4.49-21.25% compared with that of the control. This may be attributed to the alteration of cellular membrane. However, growth of first, second, and third passages of treated cells was comparable with that of the control, which may be attributed to the resealing of transient pores on the cellular membrane. Electroporation also increased (P<0.05) assimilation of cholesterol by treated parent cells (>185.40%) and first passage (>21.72%) compared with that of the control. Meanwhile, incorporation of cholesterol into the cellular membrane was also increased (P<0.05) in the treated parent cells (>108.33%) and first passage (>26.67%), accompanied by increased ratio of cholesterol:phospholipids (C:P) in these passages. Such increased ratio was also supported by increased enrichment of cholesterol in the hydrophilic heads, hydrophobic tails, and the interface regions of the membrane phospholipids of both parent and first passage cells compared with that of the control. However, such traits were not inherited by the subsequent second and third passages. Parent cells also showed decreased intestinal adherence ability (P<0.05; decreased by 1.45%) compared with that of the control, without inheritance by subsequent passages of treated cells. Our data suggest that electoporation could be a potential physical treatment to enhance the cholesterol removal ability of lactobacilli that was inherited by the first passage of treated cells without affecting their intestinal adherence ability. Keywords: Electroporation, lactobacilli, cholesterol, membrane, incorporation, passage Lactobacilli are the most common type of bacteria that exert probiotic properties. Probiotics have been defined by the FAO/WHO as “viable microorganisms which when administered in adequate amounts confer a health benefit to the host” [8]. They have been reported to exhibit several health beneficial effects such as improvement of intestinal microbial balance, prevention/reduction of diarrhea, stimulation of immune system, and prevention of gastrointestinal infection. In addition, a lowering effect on serum cholesterol by lactobacilli was also observed when minipigs were fed with meal supplemented with lactobacilli cells [6]. Xie et al. [26] also reported that the serum total cholesterol, low- density lipoprotein cholesterol, and triglycerides levels in rats were decreased upon consumption of lactobacilli. We have also previously found that the cholesterol removal ability of lactobacilli was mainly due to assimilation of cholesterol and incorporation of cholesterol into the cellular membrane [16, 17]. This reduction of cholesterol in vivo and removal of cholesterol in vitro by lactobacilli could play an important role in modulating the human cardiovascular disease, where a 1% reduction in serum cholesterol could reduce the risk of coronary heart disease by 2-3% [20]. Electroporation induces permeabilization of cell membrane via changing membrane dielectric properties [23]. This treatment is a three-step process that involves the creation, expansion, and resealing of transient pores [10]. The formation of pores as a response to electric field lasts for a few microseconds, followed by the expansion of pore size in a time range of 100 µs, and resealing of pores in the minute range. This enables the transportation of molecules from medium into the cells within the range of millisecond and minute [13]. An electric field is also known to affect mainly the cellular membranes and cause leakage of cell components via pore formation that subsequently leads to cell death. The reversible or irreversible pore formations are dependent on treatment conditions. Uptake of macromolecules without loss of viability can be observed during formation of reversible pores upon low and sublethal field strengths *Corresponding author Phone: +604 653 2114; Fax: +604 657 3678; E-mail: mintze.liong@usm.my