A preliminary study on the enzymatic biotransformation of ginsenosides is evaluated. β-Galactosidase from Aspergillus sp. displayed β-glucosidase activity, which was responsible for its ability to transform major ginsenoside Rb1 to rare ginsenoside F2 via ginsenoside Rd. The Rb1 conversion, Rd and F2 yields reached 100%, 80.7% and 14.3% after 60 h at 60 °C, respectively. Ginsenoside Rg3 can be selectively hydrolyzed and only Rh2 was obtained with this β-galactosidase as well. Before hydrolysis, an Rg3 inclusion complex was prepared with hydroxypropyl-β-cyclodextrin (HP-β-CD) to improve the aqueous solubility. The solubility of Rg3 increased 74.6 fold, and the phase solubility curve displayed a typical AL-type, which indicates the formation of a 1 : 1 inclusion complex. Using an enzyme loading of 500 U g−1 Rg3, the highest Rg3 conversion of 90.6% and Rh2 yield of 88.5% were obtained after 24 h at 60 °C. These results indicate that β-galactosidase from Aspergillus sp. could be useful for the mass production of rare ginsenosides.
Xu Geng,Yan Wei,Yuanxin Li,Siqi Zhao,Zhengqiang Li,Heng Li,Chen Li
Microbial attack, particularly fungal degradation of cellulose, is a leading cause of paper damage. To address fungal spores and the rising concern of microbial drug resistance, a nano-Germanium dioxide (GeO2)/cetyltrimethylammonium bromide (CTAB) complex (nano-GeO2/CTAB complex) with potent antibacterial properties was synthesized. Its inhibitory effects were evaluated against bacteria, including Gram-positiveStaphylococcus aureusand Gram-negativeEscherichia coli, as well as fungi isolated from paper (Fusariumspp.,Aspergillusspp., andPenicillium citrinum). The nano-GeO2/CTAB complex exhibited significant (p< 0.05) inhibitory effects againstS. aureusandE. coli. Moreover, a 60 min treatment with 1 mg/mL of the complex significantly inhibited the growth of all tested fungi and reduced their biomass after five days of culture, while 4 mg/mL completely deactivated spores. Filter paper pre-treated with the nano-GeO2/CTAB complex showed complete resistance to microbial attack, exhibiting no fungal growth and a clear inhibition zone devoid of bacterial growth. In contrast, untreated controls displayed fungal coverage exceeding 95% within five days. These findings highlight the nano-GeO2/CTAB complex as a promising antimicrobial agent for protecting paper materials from microbial degradation.
Different storage conditions can influence microbial community structure and metabolic functions, affecting rice grains’ quality. However, the microbiological mechanisms by which different storage conditions affect the quality of rice grains are not yet well understood. This study monitored the quality (the content of starch, protein, etc.) and microbial community structure of rice grains stored under different storage conditions with nitrogen gas atmosphere (RA: normal temperature, horizontal ventilation, RB: normal temperature, vertical ventilation, RC: quasi-low temperature, horizontal ventilation). The results revealed that the rice grains stored under condition RB exhibited significantly lower quality compared to condition RA and RC. In addition, under this condition, the highest relative abundance ofAspergillus(16.0%) andPenicillium(0.4%) and the highest levels of aflatoxin A (3.77 ± 0.07 μg/kg) and ochratoxin B1 (3.19 ± 0.05 μg/kg) were detected, which suggested a higher risk of fungal toxin contamination. Finally, co-occurrence network analysis was performed, and the results revealed that butyl 1,2-benzenedicarboxylate was negatively correlated (p< 0.05) withMoesziomycesandAlternaria. These findings will contribute to the knowledge base of rice storage management and guide the development of effective control measures against undesirable microbial activities.Keywords:rice grains storage;mycotoxins;microbial communities
危险品化学品经营许可证（带存储）