Continuous production of Ginsenoside Rd directly from crude saponin mixtures via a biocatalytic membrane reactor with rational interface design

In the modernization of pharmaceutical manufacturing, the efficient valorization of complex natural extracts is frequently bottlenecked by the trade-off between conversion yield and substrate stability. While conventional biocatalytic membrane reactors (BMRs) target purified substrates, processing crude micellar extracts remains a formidable challenge. Herein, we report a BMR for the continuous, green production of high-value Ginsenoside Rd from crude Panax notoginseng saponins (PNS). Addressing the specific challenge of catalyzing bulky micellar substrates, a rational interface design was employed. Guided by structural analysis of β-glucosidase (BGL), a “spacer arm” architecture utilizing polyethyleneimine (PEI) was constructed to overcome steric hindrance, with BGL site-specifically anchored via genipin (GNP). This design not only ensured active site accessibility but also restricted conformational unfolding, conferring exceptional robustness to the biocatalyst. Crucially, the transition to continuous flow operation resolved the “yield-purity” dilemma inherent to batch processing. By precisely decoupling the residence time from the operation time, the BMR effectively suppressed the non-selective degradation of the saponin matrix, a side-reaction that severely compromises product purity in conventional reactors. This process intensification enabled a seamless integration with solvent-free product recovery, delivering high-purity Rd (>82.9%) with a low Mass Intensity (MI) of 7.79. This work establishes a scalable and generic paradigm for the high-efficiency processing of chemically sensitive natural product.