Surfactant-modified yeast whole-cell biocatalyst displaying lipase on cell surface for enzymatic production of structured lipids in organic media.

The cell surface engineering system, in which functional proteins are genetically displayed on microbial cell surfaces, has recently become a powerful tool for applied biotechnology. Here, we report on the surfactant modification of surface-displayed lipase to improve its performance for enzymatic synthesis reactions. The lipase activities of the surfactant-modified yeast displaying Rhizopus oryzae lipase (ROL) were evaluated in both aqueous and nonaqueous systems. Despite the similar lipase activities of control and surfactant-modified cells in aqueous media, the treatment with nonionic surfactants increased the specific lipase activity of the ROL-displaying yeast in n-hexane. In particular, the Tween 20-modified cells increased the cell surface hydrophobicity significantly among a series of Tween surfactants tested, resulting in 8-30 times higher specific activity in organic solvents with relatively high log P values. The developed cells were successfully used for the enzymatic synthesis of phospholipids and fatty acid methyl esters in n-hexane, whereas the nontreated cells produced a significantly low yield. Our results thus indicate that surfactant modification of the cell surface can enhance the potential of the surface-displayed lipase for bioconversion.