To clarify the mechanisms underlying the growth-promoting effects of yam polysaccharide on Streptococcus thermophilus (S. thermophilus), the yam polysaccharide was extracted using a deep eutectic solvents (DESs) method and separated into four fractions by DEAE-cellulose 52. These fractions were used as the alternative carbon source to substitute lactose to compare their growth-promoting effects on S. thermophilus. Furthermore, their molecular weight, monosaccharide and functional groups’ composition, microscopic forms and other basic structure characterizations were analyzed. The results showed that all the fractions could significantly promote S. thermophilus growth, and fractions exhibited significantly different growth-promoting effects, whose viable count increased by 6.14, 6.03, 11.48 and 11.29%, respectively, relative to those in the M17 broth medium. Structure-activity relationship analysis revealed that the high growth-promoting activity of yam polysaccharide might be more dependent on the higher molecular weight, the higher galacturonic acid content and its complex spatial configuration, and the existence of β-glycosides would make the yam polysaccharide have a better growth-promoting effect on S. thermophilus.

Efficient component separation technology is one of the key ways to improve the efficiency of lignocellulose bioconversion. In this study, the formic acid method was used to separate the components of lignocellulose from Miscanthus lutarioriparius, hemicellulose was degraded into xylose simultaneously, and the composition and structure of the separated components were analyzed. Then, xylose was further purified with activated carbon for decolorization and resins for the removal of formic acid and other monosaccharide impurities. The results showed that formic acid could effectively separate the cellulose, hemicellulose, and lignin of lignocellulose with recoveries of 91.7%, 80.2%, and 85.3%, respectively. Structural analyses revealed that the cellulose and lignin underwent different degrees of formylation during the formic acid treatment, yet their primary structures remained intact, and the crystallinity of cellulose increased significantly. By GC–MS and HPLC analysis, xylose was the main component of hemicellulose extract, accounting for 74.90%. The activated carbon treatment decolorized the xylose extract more than 93.66% and gave a xylose recovery of 88.58%. D301 resin could effectively remove more than 99% of the formic acid residue in xylose. The xylose extract was further purified by removing arabinose and other monosaccharide impurities with Dowex 50wx4 resin, which increased the purity to 95%. The results demonstrated that the formic acid method is an effective method to separate lignocellulose and prepare xylose, and it has broad application prospects in the field of bio-refining lignocellulose resources such as Miscanthus lutarioriparius