Microbial Biosurfactants: A Bridge from Aquatic Environments to Subsurface Oil Recovery: Mechanisms, Challenges, Prospects.

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. The primary aim of this review is to provide an integrative understanding of how these biomolecules function at the interface between aquatic microbial ecology and subsurface petroleum engineering, with a particular focus on wettability alteration as a key mechanism for enhancing oil recovery. This review surveys major biosurfactant classes-glycolipids, lipopeptides, and polymeric bioemulsifiers-and their core mechanisms, emphasizing their relevance to challenging reservoir conditions such as high temperature and salinity. A detailed assessment is devoted to persistent hurdles such as stability, 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 are reviewed to drive the advancement of robust, green microbial-enhanced oil recovery (MEOR) technologies, charting a course from fundamental insights to field-scale implementation.