Two-step optimization of solid-state fermentation conditions of heilong48 soybean variety for maximum chlorogenic acid extraction yield with improved antioxidant activity

This study sought to establish an optimized solid-state fermentation (SSF) conditions for extraction of chlorogenic acid (CA) from heilong48 soybean (HS) variety using two-step process: Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) systematically. Both designs revealed the significant screened and optimum SSF conditions as pH (5.02), incubation time (11.52 h), inoculation size (5.00 %) and liquid-solid ratio (0.67). CA yield (8.80 +/- 0.08 mg/g), fermentation efficiency (31.29 +/- 0.28 %), and antioxidant activity (DPPH) (77.45 +/- 0.60 mu mol AA eq/g dry sample) obtained were acceptable (desirability, 1.00). Both the relative errors and the residual standard errors obtained for the predicted and experimental values were less than 5%. Higher (p < 0.05) CA yield and DPPH were obtained for the Lactobacillus casei fermented HS variety (LCFHS) than that of the unfermented HS variety (RHSF). The effectiveness of the optimized SSF conditions on the degradation of the cell wall of HS variety was affirmed by Scanning electron microscopy (SEM), Atomic force microscopy (AFM) and Fourier transform infrared (FTIR) results. The optimized extraction process was feasible, and HS variety could be used for CA extraction.