Dynamic interactions of lactic acid bacteria in Korean sourdough during back-slopping process.

AIMS: This study aimed to clarify the cause of quality reduction in Korean sourdough after successive back-slopping. METHODS AND RESULTS: We investigated the dynamic changes in lactic acid bacteria during the back-slopping process using genetic fingerprinting techniques. During the initial propagation phases, the dominant lactic acid bacteria were Fructilactobacillus sanfranciscensis (<5 log CFU per g sourdough), Latilactobacillus curvatus (9·5 log CFU per g sourdough) and Levilactobacillus brevis (6·5 log CFU per g sourdough). However, after the 11th propagation, F. sanfranciscensis became more prominent (>9·0 log CFU per g sourdough), whereas L. curvatus and L. brevis rapidly decreased. Monitoring these bacteria in the co-culture system revealed that acid-tolerant F. sanfranciscensis rapidly utilized maltose (1·65 g l-1  h-1 ) and produced large amounts of lactic acid, whereas L. brevis and L. curvatus consumed maltose slowly and L. curvatus was poorly tolerant to lactic acid. CONCLUSION: The results indicate that competition exists between the lactic acid bacteria in sourdough during the back-slopping process, and microbial succession by acid-tolerant species results in quality reduction of sourdough. SIGNIFICANCE AND IMPACT OF THE STUDY: This study uncovered the cause of microbial changes during the propagation of Korean sourdough and proposed a strategy to develop starters to produce high-quality bakery products.

Structure-activity relationships of apio nucleosides as potential antiviral agents.

Several types of novel apio nucleosides were synthesized starting from 1,3-dihydroxyacetone and evaluated for antiviral activity. Among compounds tested, amino substituted apio dideoxynucleosides exhibited anti-HBV activity, while thioapio dideoxynucleosides were found to be active against HIV-1. Apio dideoxydidehydro nucleosides showed moderate to potent anti-HCMV activity, but their bioisosteric thioapio dideoxydidehydro nucleosides did not exhibit any significant antiviral activity.