A new way of producing pediocin in Pediococcus acidilactici through intracellular stimulation by internalized inulin nanoparticles

Sang-Mok Lee,Jun-Yeong Lee,Sang-Kee Kang,Lian-Hua Cui,Sushila Maharjan,Whee-Soo Kim,Yun-Jaie Choi,Bijay Singh,Ki-June Lee,Girak Kim,Chong-Su Cho,Cheol-Heui Yun,Liang Hong

doi:10.1038/s41598-018-24227-z

Abstract

One of the most challenging aspects of probiotics as a replacement for antibiotics is to enhance their antimicrobial activity against pathogens. Given that prebiotics stimulate the growth and/or activity of probiotics, we developed phthalyl inulin nanoparticles (PINs) as prebiotics and observed their effects on the cellular and antimicrobial activities of Pediococcus acidilactici (PA). First, we assessed the internalization of PINs into PA. The internalization of PINs was largely regulated by glucose transporters in PA, and the process was energy-dependent. Once internalized, PINs induced PA to produce substantial amounts of antimicrobial peptide (pediocin), which is effective against both Gram-positive (Salmonella Gallinarum) and Gram-negative (Listeria monocytogenes) pathogens. When treated with small-sized PINs, PA witnessed a nine-fold increase in antimicrobial activity. The rise in pediocin activity in PA treated with PINs was accompanied by enhanced expression of stress response genes (groEL, groES, dnaK) and pediocin biosynthesis genes (pedA, pedD). Although the mechanism is not clear, it appears that the internalization of PINs by PA causes mild stress to activate the PA defense system, leading to increased production of pediocin. Overall, we identified a prebiotic in nanoparticle form for intracellular stimulation of probiotics, demonstrating a new avenue for the biological production of antimicrobial peptides.

Highlights

Prebiotics are generally defined as non-digestible materials that stimulate the growth and/or activity of probiotics and/or other microorganisms in the gastrointestinal (GI) tract to confer favorable health effects on the host[1]
The morphologies of the phthalyl inulin nanoparticles (PINs) were spherical with nanometer sizes when observed using a scanning electron microscope (SEM), and the number of smaller nanoparticles was greater in PIN4 as a consequence of the higher content of phthalic acid groups (Fig. 1B)
The sizes of the nanoparticles measured by dynamic light scattering (DLS) were 365, 330, 320 and 224 nm for PIN1, PIN2, PIN3 and PIN4, respectively, signifying that the particle sizes of PINs decreased in the following order (PIN1 > PIN2 > PIN3 > PIN4) with an increase in conjugated phthalic acid groups in PINs (Supplementary Fig. 1B)

Summary

Introduction

Prebiotics are generally defined as non-digestible materials that stimulate the growth and/or activity of probiotics and/or other microorganisms in the gastrointestinal (GI) tract to confer favorable health effects on the host[1]. A number of strategies, including biological, physical, and chemical methods, have emerged to enhance the production of bacteriocins from probiotics. Polymeric nanoparticles have been widely used in biomedical applications because they can deliver chemotherapeutics, proteins, genes and contrast agents as cargoes to the desired place of action or in response to specific biological or external stimuli[9]. They can be used to overcome cellular barriers for the delivery of hydrophobic drugs and macromolecules inside cells as polymeric nanoparticles that are internalized with cellular membranes into vesicles during endocytosis[10]. To the best of our knowledge, this is the first report to demonstrate improved antimicrobial activity of probiotics using a prebiotic in nanoparticle form

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