Effect of osmanthus hydrolat on the aroma quality and volatile components of osmanthus black tea

Osmanthus fragrans is an evergreen shrub with a pleasant fragrance and a wide range of applications in many fields. The condensed hydrolat obtained during the drying process of its fresh flowers was collected in a low-temperature vacuum environment and its sensory evaluation and volatile components were studied. The main aroma compounds in Osmanthus fragrans were dihydro-β-ionone, nonanal, β-cyclocitral, β-ionone, benzaldehyde, α-ionone, and 6-methyl-5-hepten-2-one, whose contents were used as the main evaluation criteria, and the hydrolats obtained under different scenting and drying times were compared. This process can effectively collect the aroma components in Osmanthus fragrans and the optimal drying conditions were 50 °C for 5 h. The hydrolat was used to provide the scent of osmanthus black tea, which had a fresher and mellower taste, while the fragrance of osmanthus was abundant. These results show that osmanthus hydrolat can be used to provide the scent of floral black tea.

Chemical compounds studied in this article

(-)-Catechin (PubChem CID: 1203); (-)-epigallocatechin gallate (PubChem CID: 65064); (-)-epicatechin gallate (PubChem CID: 367141); (-)-epigallocatechin (PubChem CID: 72277); (-)-epicatechin (PubChem CID: 72276); (-)-gallocatechin gallate (PubChem CID: 199472); (-)-catechin gallate (PubChem CID: 6419835); (-)-gallocatechin (PubChem CID: 9882981).

Isolation, Identification and Characteristic Analysis of Plant Endophyte Electrogenic Bacteria Shinella zoogloeoides SHE10

Electroactive microorganisms play a significant role in microbial fuel cells (MFCs). These devices are environmentally friendly and can turn large quantities of organic material into renewable energy based on microbial diversity. Based on broad microbial diversity, it is necessary to obtain a comprehensive understanding of their resource distribution and to discover potential resources. In this study, sweet potato tissues were selected to isolate endophytic bacteria, and the electrochemical activity potential of those bacteria was evaluated by high-throughput screening with a WO₃ nanoprobe. This study was screened and obtained a strain SHE10 with electrochemical performance from the rhizome of sweet potato by a WO₃ nanoprobe, which was identified as Shinella zoogloeoides. After nearly 600 h of voltage monitoring and cyclic voltammetry analysis, the results showed that the average voltage of S. zoogloeoides SHE10 reached 122.5 mV in stationary period. The maximum power density is 78.3 ± 1.8 mW/m², and the corresponding current density is 223.0 mA/m². The good redox reaction also indicated that the strain had good electrical activity. Its electron transfer mode was diverse, but its power generation mechanism still needs to be further discussed. The study of S. zoogloeoides SHE10 provides scientific theoretical reference for expanding the resource pool of electroproducing bacteria and the types of electroproducing microorganisms.

Plant endophytic bacteria: A potential resource pool of electroactive micro-organisms

AIMS

Electroactive micro-organisms play a significant role in microbial fuel cells. It is necessary to discover potential resources in plant endophytes. In this study, plant tissues were selected to isolate endophytic bacteria, and the electrochemical activity potential was evaluated.

METHODS AND RESULTS

The microbial fuel cell (MFC) is used to evaluate the electricity-producing activity of endophytic bacteria in plant tissues, and the species distribution of micro-organisms in the anode of the MFC after inoculation of plant tissues is determined by high-throughput sequencing. Twenty-six strains of bacteria were isolated from plant tissues belonging to Angelica and Sweet Potato, of which 17 strains from six genera had electrochemical activity, including Bacillus sp., Pleomorphomonas sp., Rahnella sp., Shinella sp., Paenibacillus sp. and Staphylococcus sp. Moreover, the electricity-producing micro-organisms in the plant tissue are enriched. Pseudomonas and Clostridioides are the dominant genera of MFC anode inoculated with angelica tissue. Staphylococcus and Lachnoclostridium are the dominant genera in MFC anode inoculated with sweet potato tissue. And the most representative Gram-positive strain Staphylococcus succinus subsp. succinus H6 and plant tissue were further analysed for electrochemical activity. And a strain numbered H6 and plant tissue had a good electrogenerating activity.

CONCLUSION

This study is of great significance for expanding the resource pool of electricity-producing micro-organisms and tapping the potential of plant endophytes for electricity-producing.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first study to apply plant endophytes to MFC to explore the characteristics of electricity production. It is of great significance for exploring the diversity of plant endophytes and the relationship between electricity producing bacteria and plants.