An Anionic Polymer Incorporating Low Amounts of Hydrophobic Residues Is a Multifunctional Surfactant. Part 2: Emulsification, Moisture Absorption, and Moisture Retention of Alkyl Esterified Poly-γ-Glutamic Acid

Makoto Urai^1,2*, Tomoko Aizawa¹, Mutsuyasu Nakajima¹, Michio Sunairi¹

¹Laboratory of Molecular Microbiology, Department of Applied Biological Science, College of Bioresource Sciences, Nihon University, Fujisawa, Japan.
²Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo, Japan.

DOI: 10.4236/aces.2015.52020                

Abstract

In the accompanying paper (Part 1), we showed that the fatty acid moiety and the acidity of the polysaccharide-backbone of a fatty acid-containing polysaccharide might be involved in its emul-sification, moisture absorption, and moisture retention abilities. In this study, we synthesized alkyl esterified poly-γ-glutamic acid (PGA) with various chain lengths and degrees of substitution of the alkyl moieties to examine how hydrophobic groups incorporated in the anionic polymer contribute to enhanced emulsification, moisture absorption, and moisture retention. With a low degree of alkylation of PGA, these abilities were drastically improved. To improve the moisture absorption of PGA, alkylation with a short chain length is effective in forming interspaces between PGA chains to trap water molecules. Hydrophobic-hydrophilic balance may also be important to improve the emulsification and moisture retention abilities of PGA alkylates. To the best of our knowledge, this is the first report of the relationship between the structure and the multifunctional abilities of an anionic polymer incorporated with a small amount of hydrophobic residue. PGA alkylates, as well as fatty acid-containing polysaccharides, have potential use as multifunctional surfactants throughout various industries.

Keywords

Poly-γ-Glutamic Acid (PGA), Alkyl Ester, Emulsification, Moisture Absorption, Moisture Retention

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Iwabuchi, N., Sunairi, M., Urai, M., Itoh C., Anzai, H., Nakajima, M. and Harayama, S. (2002) Extracellular Polysaccharides of Rhodococcus rhodochrous S-2 Stimulate the Degradation of Aromatic Components in Crude Oil by Indigenous Marine Bacteria. Applied and Environmental Microbiology, 68, 2337-2343. http://dx.doi.org/10.1128/AEM.68.5.2337-2343.2002
[2]	Urai, M., Anzai, H., Ogihara, J., Iwabuchi, N., Harayama, S., Sunairi, M. and Nakajima, M. (2006) Structural Analysis of an Extracellular Polysaccharide Produced by Rhodococcus rhodochrous Strain S-2. Carbohydrate Research, 341, 766-775. http://dx.doi.org/10.1016/j.carres.2005.12.013
[3]	Aizawa, T., Neilan, B., Couperwhite, I., Urai, M., Anzai, H., Iwabuchi, N., Nakajima, M. and Sunairi, M. (2005) Relationship between Extracellular Polysaccharide and Benzene Tolerance of Rhodococcus sp. 33. Actinomycetologica, 19, 1-6. http://dx.doi.org/10.3209/saj.19.1
[4]	Urai, M., Aizawa, T., Anzai, H., Ogihara, J., Iwabuchi, N., Neilan, B., Couperwhite, I., Nakajima, M. and Sunairi, M. (2006) Structural Analysis of an Extracellular Polysaccharide Produced by a Benzene Tolerant Bacterium, Rhodococcus sp. 33. Carbohydrate Research, 341, 616-623. http://dx.doi.org/10.1016/j.carres.2006.01.010
[5]	Urai, M., Yoshizaki, H., Anzai, H., Ogihara, J., Iwabuchi, N., Harayama, S., Sunairi, M. and Nakajima, M. (2007) Structural Analysis of an Acidic, Fatty Acid Ester-Bonded Extracellular Polysaccharide Produced by a Pristane-Assimilating Marine Bacterium, Rhodococcus erythropolis PR4. Carbohydrate Research, 342, 933-942. http://dx.doi.org/10.1016/j.carres.2007.02.001
[6]	Urai, M., Yoshizaki, H., Anzai, H., Ogihara, J., Iwabuchi, N., Harayama, S., Sunairi, M. and Nakajima, M. (2007) Structural Analysis of Mucoidan, an Acidic Extracellular Polysaccharide Produced by a Pristane-Assimilating Marine Bacterium, Rhodococcus erythropolis PR4. Carbohydrate Research, 342, 927-932. http://dx.doi.org/10.1016/j.carres.2007.02.002
[7]	Urai, M., Anzai, H., Iwabuchi, N., Sunairi, M. and Nakajima, M. (2002) A Novel Moisture-Absorbing Extracellular Polysaccharide from Rhodococcus rhodochrous SM-1. Actinomycetologica, 16, 26-31. http://dx.doi.org/10.3209/saj.16_26
[8]	Urai, M., Anzai, H., Iwabuchi, N., Sunairi, M. and Nakajima, M. (2004) A Novel Viscous Extracellular Polysaccharide Containing Fatty Acids from Rhodococcus rhodochrous ATCC 53968. Actinomycetologica, 18, 15-17. http://dx.doi.org/10.3209/saj.18_15
[9]	Shih, I.L. and Van, Y.T. (2001) The Production of Poly-(gamma-glutamic acid) from Microorganisms and Its Various Applications. Bioresource Technology, 79, 207-225. http://dx.doi.org/10.1016/S0960-8524(01)00074-8
[10]	Kunioka, M. (1997) Biosynthesis and Chemical Reactions of Poly(amino acid)s from Microorganisms. Applied Microbiology and Biotechnology, 47, 469-475. http://dx.doi.org/10.1007/s002530050958
[11]	Kubota, H., Nambu, Y. and Endo, T. (1995) Convenient Esterification of Poly(γ-glutamic acid) Produced by Microorganism with Alkyl Halides and Their Thermal Properties. Journal of Polymer Science Part A: Polymer Chemistry, 33, 85-88. http://dx.doi.org/10.1002/pola.1995.080330110
[12]	Dong, C. and Tian, B. (1999) Studies on Preparation and Emulsifying Properties of Guar Galactomannan Ester of Palmitic Acid. Journal of Applied Polymer Science, 72, 639-645. http://dx.doi.org/10.1002/(SICI)1097-4628(19990502)72:5<639::AID-APP4>3.0.CO;2-K
[13]	Shimokuri, T., Kaneko, T., Serizawa, T. and Akashi, M. (2004) Preparation and Thermosensitivity of Naturally Occurring Polypeptide Poly(γ-glutamic acid) Derivatives Modified by Propyl Groups. Macromolecular Bioscience, 4, 407- 411. http://dx.doi.org/10.1002/mabi.200300073
[14]	Buchholz, F.L. and Peppas, N.A. (1994) Superabsorbent Polymers Science and Technology. ACS Symposium Series, 573, 160p. http://dx.doi.org/10.1021/bk-1994-0573