The significant demand for medicinal plants with special efficacy has prompted us to adopt appropriate processing methods to enhance the nutritional quality and flavor of raw materials. This study evaluated the impacts of freeze-drying (FD), hot-air drying (HAD), and spray drying (SD) on the bioactive compounds, flavor characteristics, and inhibition of starch digestion in mulberry leaf ethanol extract (MLE). Results indicated that FDMLE exhibited the highest total alkaloids content (TAC: 0.14 ± 0.02 mg/g) and total flavonoid content (TFC: 19.32 ± 0.58 mg/g), along with significant inhibitory effects on starch hydrolysis at 180 min (starch hydrolysis rate <50%). The microstructure of HADMLE was closest to that of the mulberry leaf powder (ML), but SD better preserved the color of ML (ΔE = 1.55 ± 0.04). Combined with the electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS) found HAD processing facilitated the conversion of flavor precursors in ML into Ethyl formate, rose oxide, and (Z)-3-hexenol (M). SDMLE contained higher levels of pentanal, (E)-2-hexenal (D), (E)-2-pentanone, 3-Methyl-2-butenal (D), ethyl butyrate, and 1-penten-3-one (D). FDMLE exhibited the highest diversity of novel volatile compounds (VOCs), with 18 newly identified species. In conclusion, FD is a potential method to effectively reduce the degradation of quality and efficacy of MLE during the drying process.

Soybean molasses, a by-product of alcohol-based soy protein concentrate production, is rich in stachyose and other functional oligosaccharides, but its high sucrose content and other fermentable non-target sugars hinder the efficient purification of stachyose. In this study, the sugar-utilization patterns of four commonly used microbial chassis or production strains, Escherichia coli W, E. coli BL21, Saccharomyces pastorianus Weihenstephan 34/70, and Komagataella phaffii (formerly Pichia pastoris) GS115, were systematically compared to identify a suitable host for selective stachyose enrichment. Among them, E. coli W showed the best performance in rapidly consuming non-target sugars while retaining stachyose. Based on this strain, a CRISPR–Cas9 engineering strategy was applied by deleting the endogenous α-galactosidase gene melA and overexpressing the sucrose permease gene cscB. The resulting strain selectively and nearly completely removed sucrose and other non-target sugars from soybean molasses, increasing the proportion of stachyose from 90% of total soluble solids. Further optimization of nitrogen source level, inoculum size, and initial °Brix improved fermentation performance. These results demonstrate an effective biological pre-purification strategy for selective stachyose enrichment from soybean molasses.