Application of polyhydroxyalkanoate (PHA) synthesis regulatory protein PhaR as a bio-surfactant and bactericidal agent.

Polyhydroxyalkanoates (PHA), a family of diverse bio-polyesters, are produced by many bacteria as an energy and carbon storage material. PHA synthesis regulatory protein PhaR was reported to attach on the surface of intracellular PHA granules for convenience of synthesis regulation. PhaR was found to have an amphiphilic property. However, no study was conducted to exploit this property for applications as bio-surfactant and bactericide agent. Purified PhaR showed a higher emulsification ability than that of the widely used chemical surfactants including SDS, Tween 20, sodium oleate, and liquefied detergent (LD). PhaR also showed a higher emulsification ability than bio-surfactants rhamnose and PHA granules associated protein termed phasin or PhaP. Non-purified PhaR, namely, the native inclusion bodies and cell lysates, also demonstrated to be an excellent surfactant. PhaR was found highly stable even at 95 °C. In addition, PhaR was revealed to be a promising bactericidal agent against Gram positive and negative bacteria. PhaR can be conveniently produced by recombinant Escherichia coli. It has shown to be a bio-surfactant with excellent emulsification ability and strong bactericidal capacity at elevated temperature as high as 95 °C. Therefore, PhaR could be used in areas including food, beverage, pharmaceutical and cosmetics industries.