Poly-γ-Glutamic Acid: Biodegradable Polymer for Potential Protection of Beneficial Viruses

Ibrahim R Khalil; Victor U Irorere; Iza Radecka; Alan T H Burns; Marek Kowalczuk; Jessica L Mason; Martin P Khechara

doi:10.3390/ma9010028

Poly-γ-Glutamic Acid: Biodegradable Polymer for Potential Protection of Beneficial Viruses

Materials (Basel). 2016 Jan 6;9(1):28. doi: 10.3390/ma9010028.

Authors

Ibrahim R Khalil^{1

2}, Victor U Irorere³, Iza Radecka⁴, Alan T H Burns⁵, Marek Kowalczuk^{6

7}, Jessica L Mason⁸, Martin P Khechara⁹

Affiliations

¹ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. Ibrahim.khalil@wlv.ac.uk.
² Department of Biology, College of Science, Tikrit University, Tikrit PO Box 42, Iraq. Ibrahim.khalil@wlv.ac.uk.
³ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. Irorere-V@email.ulster.ac.uk.
⁴ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. I.Radecka@wlv.ac.uk.
⁵ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. A.T.Burns@wlv.ac.uk.
⁶ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. M.Kowalczuk@wlv.ac.uk.
⁷ Center of Polymer and Carbon Materials, Polish Academy of Sciences, ul. M. Curie-Skłodowskiej 34, Zabrze 41-819, Poland. M.Kowalczuk@wlv.ac.uk.
⁸ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. J.Mason@wlv.ac.uk.
⁹ Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1LY, UK. mpkhechara@wlv.ac.uk.

Abstract

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, non-toxic and non-immunogenic properties has been used successfully in the food, medical and wastewater industries. A major hurdle in bacteriophage application is the inability of phage to persist for extended periods in the environment due to their susceptibility to environmental factors such as temperature, sunlight, desiccation and irradiation. Thus, the aim of this study was to protect useful phage from the harmful effect of these environmental factors using the γ-PGA biodegradable polymer. In addition, the association between γ-PGA and phage was investigated. Formulated phage (with 1% γ-PGA) and non-formulated phage were exposed to 50 °C. A clear difference was noticed as viability of non-formulated phage was reduced to 21% at log₁₀ 1.3 PFU/mL, while phage formulated with γ-PGA was 84% at log₁₀ 5.2 PFU/mL after 24 h of exposure. In addition, formulated phage remained viable at log₁₀ 2.5 PFU/mL even after 24 h of exposure at pH 3 solution. In contrast, non-formulated phages were totally inactivated after the same time of exposure. In addition, non-formulated phages when exposed to UV irradiation died within 10 min. In contrast also phages formulated with 1% γ-PGA had a viability of log₁₀ 4.1 PFU/mL at the same exposure time. Microscopy showed a clear interaction between γ-PGA and phages. In conclusion, the results suggest that γ-PGA has an unique protective effect on phage particles.

Keywords: bacteriophage; biodegradable polymer; γ-PGA.