Natural roles of biosurfactants

Microorganisms produce a variety of surface-active agents (or surfactants), These can be divided into low-molecular-weight molecules that lower surfac e and interfacial tensions efficiently and high-molecular-weight polymers t hat bind tightly to surfaces. These surfactants, produced by a wide variety of microorganisms, have very different chemical structures and surface pro perties. It is therefore reasonable to assume that different groups of bios urfactants have different natural roles in the growth of the producing micr oorganisms. Moreover, as their chemical structures and surface properties a re so different, each emulsifier probably provides advantages in a particul ar ecological niche, Several bioemulsifiers have antibacterial or antifunga l activities, Other bioemulsifiers enhance the growth of bacteria on hydrop hobic water-insoluble substrates by increasing their bioavailability, presu mably by increasing their surface area, desorbing them from surfaces and in creasing their apparent solubility. Bioemulsifiers also play an important r ole in regulating the attachment-detachment of microorganisms to and from s urfaces. In addition, emulsifiers are involved in bacterial pathogenesis, q uorum sensing and biofilm formation. Recent experiments indicate that a hig h-molecular-weight bioemulsifier that coats the bacterial surface can be tr ansferred horizontally to other bacteria, thereby changing their surface pr operties and interactions with the environment.