Honeysuckle as a Bio-Enhancer in Monascus purpureus Fermentation: Synergistic Improvement of Monacolin K Yield and Flavor Complexity

Recently, co-fermentation of functional medicinal plants with fungi has emerged as a promising strategy to enhance the overall quality of fermented foods. Monascus fermentation products have long been confronted with bottlenecks in both functionality and palatability, such as low monacolin K (MK) yield and poor flavor. Therefore, this study investigated the effects of co-fermenting Monascus purpureus with honeysuckle (Lonicera japonica Thunb.) on the bioactive metabolites and volatile flavor compounds of the fermented product. Through single-factor optimization, the addition of 0.8 g/L honeysuckle powder was identified as optimal, resulting in a 1.54-fold increase in MK yield compared to the control. Additionally, nine key genes were upregulated in the MK biosynthetic cluster (mokA–mokI). Co-fermentation also significantly increased the total flavonoid and polyphenol contents by 3.93-and 2.01-fold, respectively, and enhanced in vitro antioxidant activity. Gas chromatography-mass spectrometry analysis revealed that ketones, esters, and alcohols were the dominant volatile compounds. Orthogonal partial least squares-discriminant analysis identified 11 differential volatile compounds (variable importance in projection > 1), indicating a substantial shift in the flavor profile toward more desirable notes, with a reduction in undesirable aldehydes. These findings demonstrate that honeysuckle co-fermentation enhances the biofunctional properties of M. purpureus fermentation products and improves their sensory appeal, providing a viable bioprocessing strategy for developing high-value Monascus-based functional foods or ingredients.