To optimize the ultrasonic extraction process of polysaccharides from Dendrobium nobile Lindl. (DNP), the extraction method was conducted through a single-factor test and the response-surface methodology (RSM). With the optimal extraction process (liquid–solid ratio of 40 mL/g, ultrasonic time of 30 min, and ultrasonic power of 400 W), the maximum extraction yield was 5.16 ± 0.41%. DNP1 and DNP2 were then fractionated via DEAE-QFF and Sephacryl S-300 HR chromatography. The molecular weight (Mw) of DNP1 was identified as 67.72 kDa, composed of Man (75.86 ± 0.05%) and Glc (24.14 ± 0.05%), and the Mw of DNP2 was 37.45 kDa, composed of Man (72.32 ± 0.03%) and Glc (27.68 ± 0.03%). Anti-inflammatory assays results showed that as DNPs were 200 μg/mL, and the contents of NO, TNF-α, IL-1β, IL-6 and IL-10 in LPS-induced RAW 264.7 cells were about 13.39% and 13.39%, 43.88% and 43.51%, 17.80% and 15.37%, 13.84% and 20.66%, and 938.85% and 907.77% of those in control group, respectively. It was indicated that DNP1 and DNP2 inhibited the inflammatory response of RAW 264.7 cells induced by LPS via suppressing the level of NO and pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and promoting the secretion of anti-inflammatory cytokine (IL-10). Therefore, DNP1 and DNP2 have potential applications in the treatment of inflammatory injury.

Fermentation is an effective method for enhancing the biological activity of polysaccharides, but research on its effect on Dendrobium officinal polysaccharides is rare. In this study, the effects of mono-fermentation (Saccharomyces cerevisiae FBKL2.8022, Sc; Wickerhamomyces anomalous FBKL2.8023, Wa) and co-fermentation (Sc+Wa) on the physicochemical properties and bioactivity of Dendrobium officinal polysaccharides were investigated. Meanwhile, the polysaccharide (DOP) obtained from Dendrobium officinale was used as a control. Four homogeneous polysaccharides were obtained by isolation and purification and named DOSCP, DOWAP, DOSWP, and DOP. The results showed that DOSCP, DOWAP, DOSWP, and DOP consisted of mannose and glucose with ratios of 3.31:1, 5.56:1, 2.40:1, and 3.29:1, respectively. The molecular weights (Mws) of the four polysaccharides were 25.73 kDa, 15.01 kDa, 17.67 kDa, and 1268.21 kDa. The antioxidant activity of DOSCP, DOWAP, and DOSWP was better than that of DOP. Additionally, all four polysaccharides were able to reduce the inflammatory response of LPS-induced RAW 264.7 macrophages in the mice without a significant difference. Yeast fermentation significantly reduced the molecular weight and improved the antioxidant activity of Dendrobium officinale polysaccharides, indicating a potential way to improve its antioxidant activity.

Rice, supplemented with Dendrobium officinale, was subjected to cofermentation using Saccharomyces cerevisiae FBKL2.8022 (Sc) and Wickerhamomyces anomalus FBKL2.8023 (Wa). The alcohol content was determined with a biosensor, total sugars with the phenol–sulfuric acid method, reducing sugars with the DNS method, total acids and total phenols with the colorimetric method, and metabolites were analyzed using LC-MS/MS combined with multivariate statistics, while metabolic pathways were constructed using metaboAnalyst 5.0. It was found that the quality of rice wine was higher with the addition of D. officinale. A total of 127 major active substances, mainly phenols, flavonoids, terpenoids, alkaloids, and phenylpropanoids, were identified. Among them, 26 substances might have been mainly metabolized by the mixed-yeasts fermentation itself, and 10 substances might have originated either from D. officinale itself or from microbial metabolism on the newly supplemented substrate. In addition, significant differences in metabolite could be attributed to amino acid metabolic pathways, such as phenylalanine metabolism and alanine, aspartate, and glutamate metabolism. The characteristic microbial metabolism of D. officinale produces metabolites, which are α-dihydroartemisinin, alantolactone, neohesperidin dihydrochalcone, and occidentoside. This study showed that mixed-yeasts cofermentation and fermentation with D. officinale both could increase the content of active substances in rice wine and significantly improve the quality of rice wine. The results of this study provide a reference for the mixed fermentation of brewer’s yeast and non-yeast yeasts in rice wine brewing.