Super Ohtaka® (fermented beverage of plant extracts) is prepared from approximately 50 vegetables and fruits. Natural fermentation is primarily performed using lactic acid bacteria (Leuconostoc spp.) and yeast (Zygosaccharomyces spp.). An unidentified oligosaccharide was isolated from this beverage using carbon-Celite® column chromatography and high performance liquid chromatography. The oligosaccharide structure was confirmed by MALDI-TOF MS and NMR measurements. This oligosaccharide was identified as β-D-fructopyranosyl-(2→6)-β-D-glucopyranosyl-(1→6)-D-glucose, it was newly found from natural source. We speculated that this oligosaccharide was generated or enhanced during the fermentation, and was barely degraded by artificial gastric juice and rat intestinal enzymes, although it was slightly hydrolyzed by pig pancreatic enzymes.
Sweet potato (Ipomoea batatas (L.) Lam) is a widely cultivated crop valued for its nutritional and functional properties. In Japan, consumers particularly prioritize the sweetness and texture of baked sweet potatoes. Among the free sugars in cooked sweet potatoes, maltose is predominant, generated by β-amylase-mediated hydrolysis of gelatinized starch during heating. This study investigated the relationship between starch gelatinization properties and β-amylase activity in ten soggy-type sweet potato cultivars (Aikomachi, Annouimo, Beniharuka, Benimasari, Fukumurasaki, Himeayaka, Karayutaka, Kenroku, Silksweet, and Tamayutaka) and one intermediate-type standard cultivar (Kokei 14), all cultivated in the same farm. We evaluated free sugar content, starch gelatinization characteristics, amylopectin chain-length distribution, and β-amylase activity. A positive correlation was observed between the proportion of DP13-24 chains in amylopectin and the onset (T o) and peak (T p) gelatinization temperatures, as measured by differential scanning calorimetry (DSC). Himeayaka, with the highest maltose content, also showed the highest β-amylase activity. In contrast, Silksweet had similar enzyme activity but lower maltose levels. These findings indicate that starch gelatinization behavior is key to the sweetness and texture of cooked sweet potatoes. Principal component analysis grouped the cultivars into three categories: typical soggy-type, slightly soggy-type, and near intermediate-type. These insights can guide the breeding and selection of cultivars aligned with consumer preferences.
Gum arabic (GA) is a highly branched arabinogalactan-protein complex widely used in food and pharmaceutical industries. Its complex side chains contain L-arabinofuranose residues linked via α-(1→3) and α-(1→4) bonds, which represent the final structural barrier to complete enzymatic degradation of GA. Here, we isolated and characterized two complementary α-L-arabinofuranosidases, FoAF2 and FoAF3, from Fusarium oxysporum 12S. FoAF2, a glycoside hydrolase (GH) family 54 enzyme, preferentially cleaves α-(1→3)-arabinosyl residues while exhibiting weak activity toward α-(1→4) linkages at high enzyme concentrations. In contrast, the GH43_34 enzyme FoAF3 displays strict specificity for α-(1→4)-arabinosyl residues but requires prior removal of neighboring α-(1→3) substituents for efficient catalysis. Structural modeling using AlphaFold 3 revealed that the constrained catalytic pocket of FoAF3 is highly sensitive to steric hindrance from adjacent branches, explaining its dependence on sequential FoAF2 action for complete debranching. This two-enzyme system functions similarly to the bifunctional Bifidobacterium BIAraE, but achieves the same effect using separate enzymes rather than fused domains. Combined with previously characterized F. oxysporum enzymes, FoAF2 and FoAF3 complete a comprehensive toolkit enabling systematic GA degradation from complex side chains to monosaccharides. These findings provide molecular insights into the mechanisms underlying α-L-arabinofuranosidase specificity and establish a foundation for the enzymatic modification of GA for industrial applications.
