Microbial Biosurfactants: A Bridge from Aquatic Environments to Subsurface Wettability Alteration in Oil Recovery

Microbial biosurfactants, derived from diverse aquatic and extreme ecosystems, offer a sustainable and environmentally compatible strategy for enhanced oil recovery by fundamentally altering subsurface rock wettability. These biologically produced amphiphiles can efficiently transform oil-wet rock surfaces into water-wet states, thereby mobilizing otherwise trapped crude oil. This review delineates their core mechanisms: wettability alteration, interfacial tension reduction, and emulsification. Major classes of biosurfactants, including glycolipids, lipopeptides, and polymeric bioemulsifiers are surveyed, focusing particularly on their relevance to challenging reservoir conditions. A detailed assessment is devoted to persistent hurdles such as stability under high temperature and salinity, adsorption onto rock formations, and economic scalability. Future prospects center on three key approaches: advancing synergistic “bio-hybrid” systems that integrate biosurfactants with complementary agents such as biopolymers and nanomaterials; achieving cost-effective production through the valorization of waste feedstocks; and expanding targeted bioprospecting of microbial diversity from extreme aquatic environments. Together, these strategies will drive the advancement of robust, green microbial enhanced oil recovery (MEOR) technologies.