Biosurfactants for a Sustainable Future. Группа авторов
Читать онлайн книгу.
is known about their physicochemical properties.
1.8 Final Comments
Most of the isolated biosurfactants have not been characterized as deeply as sophorolipids or surfactins reviewed above. In many cases, the tiny amounts obtained prevent more careful studies and, for many of them, the cmc is the only physicochemical variable so far provided. Even the published values for cmc must be handled cautiously as the purity degree of the biosurfactant is low. However, if the biosurfactant belongs to a given family of derivatives, many of their properties can be estimated with different degrees of accuracy. Aggregation number or the change in heat capacity are provided examples in this chapter for classical and sugar surfactants. Conversely, a new measured physical quantity may be checked and compared with published values for similar compounds, although, occasionally, results (such as those obtained for some gemini surfactants) can break an accepted rule. The absence of physicochemical characterization is also related to the origin of research groups involved in their discovery, as they are more interested in biological properties and applications, as following chapters of this book will review. As classical surfactants, biosurfactants are affected by revisions of old theories or by new proposals. Although we have presented the theories and models in their simplest versions, we have also illustrated that concepts largely accepted during decades are nowadays under scrutiny.
Also, the knowledge of the structure/property relationship allows a possible improvement of some properties of a new biosurfactant by enlargement of the alkyl chain, introduction of a hydrophobic or hydrophilic residue, or the synthesis of new structures (gemini, Y‐shaped, bolaamphiphile…). All of them are nowadays well‐known options. The cooperation between chemistry and biology research groups, with a wide range of capacities, can be decisive in the improvement of desired properties and applications. Comments by Menger [217] about host–guest systems, typical examples of supramolecular entities, are valid for stimulating such a cooperation. Emulating his comments, it might be easy to design on paper a new surfactant bearing a wish‐list of optimally oriented capacities and properties. Of course, the risk will be that after spending hours (and money) in the synthesis laboratory, such a molecule does not fulfill our expectations. We have unpublished experience on several negative projects. The task may be facilitated by the ability of researchers to further develop molecules from a biological origin that are the result of evolution. Bile salts (which have been our focus of interest for the last three decades) might be good examples of previous assertions.
The steroid nucleus with some specific organic functions located at certain positions and different orientations and, mainly, its enormous transcendence in living organisms (including human beings) is the result of a billion years of evolution of nature. Although all the human scientific knowledge would not probably be able to design it from zero, we (and others) have been able to modify their hydrophobic/hydrophilic balance by attaching specific residues into the structure. As a result, the formation of initially unexpected supramolecular structures is now well documented. Publications of the potential use of these new derivatives for the formation of gels, resolution of enantiomers, complexing a single water molecule, and synthesis of new antibiotics and antidotes can be found elsewhere [218–222]. These are just examples that pretend to encourage chemical modifications on new biosurfactants that microorganisms provided us.
Acknowledgement
The authors thank the Ministerio de Economía, Industria y Competitividad (Spain) (Project MAT2017‐86109‐P) for financial support.
References
1 1 IUPAC (1997). Compendium of Chemical Terminology. (the “Gold Book”), 2e (eds. A.D. McNaught and A. Wilkinson). Oxford: Blackwell. Online version created by Chalk. S. J. ISBN: 0‐9678550‐9‐8. (2019).
2 2 Taylor, H.J. and Alexander, J. (1944). The measurement of surface tension by means of sessile drops. Proc. Indian Acad. Sci., Math. Sci. 19: 149–158.
3 3 Vargaftik, N.B., Volkov, B.N., and Voljak, L.D. (1983). International tables of the surface tension of water. J. Phys. Chem. Ref. Data Monogr. 12: 817–820.
4 4 Jasper, J.J. (1972). The surface tension of pure liquid compounds. J. Phys. Chem. Ref. Data Monogr. 1: 841–1009.
5 5 Levey, M. (1954). The early history of detergent substances: A chapter in Babylonian chemistry. J. Chem. Educ. 31: 521–524.
6 6 Mayhoff, K.F.T. (ed.) (1906). Pliny the Elders, (AD 23–79) Naturalis Historia. Lipsiae: Teubner.
7 7 Hunt, J.A. (1999). A short history of soap. Pharm. J. (1 Dec.).
8 8 Campbell, M. 1858. Improved process of making soap. US Patent Office, Patent no. 19667.
9 9 Mitchell, R.W. (1927). Castile Soap‐a Monograph Covering the Origin, History and Significance. Boston: Brackett & Co.
10 10 Schulze, E.L. (1966). Literature of soaps and synthetic detergents. Lit. Chem. Technol.: 231–248.
11 11 Phanstiel, O. IV, Dueno, E., and Wang, Q.X. (1998). Synthesis of exotic soaps in the chemistry laboratory. J. Chem. Educ. 75: 612–614.
12 12 Kastens, M.L. and Ayo, J.J. Jr. (1950). Pioneer surfactant. Ind. Eng. Chem., 42: 1626–1638.
13 13 Kosswig, K. (2012). Surfactants. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley VCH.
14 14 Kanno, S., Suzuki, A., Baba, H., and Hanzawa, Y. (1977). Structure of a Nekal‐type surfactant a ‐ commercial Twitchell reagent “Idrapidspalter”. Yukagaku 26: 789–791.
15 15 Bellon, J.L.M. & LeTellier, P.A. Surfactants. P.A. FR 881893 19430511 (1943).
16 16 Lucas, F.H. and Brown, A.H. (1950). Activity of wetting agents‐temperature effects. Food Technol. 4: 121–124.
17 17 Farn, R.J. (ed.) (2006). Chemistry and Technology of Surfactants. Oxford: Blackwell Publishing Ltd.
18 18 Attwood, D. and Florence, A.T. (2013). Surfactant Systems, Their Chemistry, Pharmacy and Biology. London: Chapman and Hall.
19 19 Meijide, F., Trillo, J.V., de Frutos, S. et al. (2013). Symbiotic and synergic effects in amide and ester derivatives of EDTA. In: EDTA: Synthesis, Uses and Environmental Concerns (ed. A. Molnar). Nova Publishers: New York.
20 20 Kaspar, F., Neubauer, P., and Gimpel, M. (2019). Bioactive secondary metabolites from Bacillus subtilis: a comprehensive review. J. Nat. Prod. 82: 2038–2053.
21 21 Zana, R. (2002). Dimeric and oligomeric surfactants. Behavior at interfaces and in aqueous solution: a review. Adv. Colloid Interface Sci. 97: 205–253.
22 22 Zana, R. and Xia, J. (eds.) (2004). Gemini Surfactants. Synthesis, Interfacial and Solution ‐Phase Behavior, and Applications, Surfactants Science Series. New York: Dekker.
23 23 Fuhrhop, J.‐H. and Wang, T. (2004). Bolaamphiphiles. Chem. Rev. 104: 2901–2937.
24 24 Gouzy, M.‐F., Guidetti, B., Andre‐Barres, C. et al. (2001). Aggregation behavior in aqueous solutions of a new class of asymmetric bipolar Amphiphiles investigated by surface tension measurements. J. Colloid Interface Sci. 239: 517–521.
25 25 Guilbot, J., Benvegnu, T., Legros, N. et al. (2001). Efficient synthesis of unsymmetrical bolaamphiphiles for spontaneous formation of vesicles and disks with a transmembrane organization. Langmuir 17: 613–618.
26 26 Baccile, N., Delbeke, E.I.P., Brennich, M. et al. (2019). Asymmetrical, symmetrical, divalent, and Y‐shaped (bola)amphiphiles: the relationship between the molecular structure and self‐assembly in amino derivatives of Sophorolipid biosurfactants. J. Phys. Chem. B 123: 3841–3858.
27 27 Hofmann, A.F. and Mysels, K.J. (1988). Bile salts as biological surfactants. Colloids Surf. 30: 145–173.
28 28 Small, D.M. (1971). The physical chemistry of Cholanic acids. In: The Bile Acids, Chemistry, Physiology, and Metabolism (eds. P.P. Nair and D. Kritchevski). Plenum Press: New York.
29 29 Savage, P.B., Li, C., Taotafa, U. et al. (2002).