Self-Emulsifying Biocatalysis Based on an Amphipathic Protein BslA-Modified Esterase Functioning as a Fine-Tuned System for Oil Hydrolysis

Traditional heterogeneous enzymatic reactions involving hydrophobic substrates rely on emulsifiers, which pose environmental risks and can destabilize enzymes. To address this problem, a self-emulsifying system based on biofilm surface layer protein A (BslA) was designed and established in this study. Taking the enzymatic hydrolysis of astaxanthin esters as an example, the emulsification capacity and hydrolysis efficiency of BslA-Est3-14 fusion protein, comprising the amphiphilic protein BslA and esterase Est3-14, was investigated. Compared with the group containing no emulsifiers, the addition of BslA-Est3-14 significantly reduced the droplet size from 3.04 μm to 1.46 μm. Additionally, the addition of BslA demonstrated competitive efficacy in maintaining enzyme activity than traditional emulsifiers. Furthermore, the BslA-Est3-14 group increased the yield of free astaxanthin by 52.3%, 78.0%, and 76.9% compared to the Tween-80, Span-20, and ethanol groups, respectively. The highest yield of astaxanthin in emulsion reaction system was finally determined to be 184 μg·mL⁻¹. This method not only mitigates the low efficiency of heterogeneous enzymatic reactions but also eliminates the requirement for surfactants, thereby minimizing environmental footprints and holding significant implications for sustainable bioprocessing in food, pharmaceutical, and green chemistry sectors.