Diversity of Plant Endophytic Volatile Organic Compound (VOC) and Their Potential Applications

Chemical profile, antibacterial and antioxidant properties of Rubia tinctorum L. essential oils

Plants have gained great importance. Secondary metabolites contribute to the drug discovery and development by their bioactive properties. Rubia tinctorum L. essential oil (EO) was obtained and analysed. Antioxidant and antibacterial activities were evaluated. The plant's EOs were obtained through steam distillation, and the compounds were identified using gas chromatography-mass spectrometry (GC-MS) analysis. DPPH free radical scavenging and ferric-reducing antioxidant power (FRAP) were employed to assess antioxidant activity. Total antioxidant capacity (TAC) was also presented. The disc diffusion method was employed for testing antibacterial activity. Cyclohexanone was identified as the predominant component in the EO, constituting 88.74% of the total composition. The EO did not show significant antioxidant capacity, while it demonstrated antimicrobial effect against Bacillus cereus ATCC 6633 (>13 mm of inhibition; 500 mg/mL) and Shigella ATCC 12022 (≥12 mm of inhibition; 500 mg/mL). R. tinctorum L. is new source of cyclohexanone.

Succession of endophytic bacterial community and its contribution to cinnamon oil production during cinnamon shade-drying process

Cinnamon oil is a blend of secondary metabolites and is widely used as spice. Endophytic bacteria are always related to the secondary metabolites production. However, the potential of endophytic bacteria communities for cinnamon oil production during cinnamon shade-drying process is still not clear. In this study, we investigated the composition and metabolic function of endophytic bacterial community during 80-day shade-drying process. The temporal dynamics of essential oil content and its dominant constituents were analyzed. The succession of endophytic bacterial community from d0 to d80 was identified. The influence of endophytic bacterial community evolution on cinnamon oil is significant positive. Predictive functional analysis indicated that shade-drying process was rich in Saccharopolyspora that produce enzymes for the conversion of phenylalanine to cinnamaldehyde. These findings enhance our understanding of the functional bacterial genera and functional genes involved in the production of cinnamon oil during cinnamon shade-drying process.

Bacillus thuringiensis RZ2MS9, a tropical plant growth-promoting rhizobacterium, colonizes maize endophytically and alters the plant's production of volatile organic compounds during co-inoculation with Azospirillum brasilense Ab-V5

The beneficial features of Bacillus thuringiensis (Bt) are not limited to its role as an insecticide; it is also able to promote plant growth interacting with plants and other plant growth-promoting rhizobacterium (PGPR). The PGPR Bt strain RZ2MS9 is a multi-trait maize growth promoter. We obtained a stable mutant of RZ2MS9 labelled with green fluorescent protein (RZ2MS9-GFP). We demonstrated that the Bt RZ2MS9-GFP successfully colonizes maize's roots and leaves endophytically. We evaluated whether RZ2MS9 has an additive effect on plant growth promotion when co-inoculated with Azospirillum brasilense Ab-V5. The two strains combined enhanced maize's roots and shoots dry weight around 50% and 80%, respectively, when compared to the non-inoculated control. However, non-differences were observed comparing RZ2MS9 alone and when co-inoculated with Ab-V5, In addition, we used co-inoculation experiments in glass chambers to analyse the plant's volatile organic compounds (VOCs) production during the maize-RZ2MS9 and maize-RZ2MS9-Ab-V5 interaction. We found that the single and co-inoculation altered maize's VOCs emission profile, with an increase in the production of indoles in the co-inoculation. Collectively, these results increase our knowledge about the interaction between the Bt and maize, and provide a new possibility of combined application with the commercial inoculant A. brasilense Ab-V5.

Termitomyces heimii Associated with Fungus-Growing Termite Produces Volatile Organic Compounds (VOCs) and Lignocellulose-Degrading Enzymes

Termitomyces fungi associated with fungus-growing termites are the edible mushrooms and can produce useful chemicals, enzymes, and volatile organic compounds (VOCs) that have both fuel and biological potentials. To this purpose, we examined the Termitomyces mycelial growth performance on various substrates, clarified lignocellulose-degrading enzyme activity, and also identified the VOCs produced by Termitomyces. Our results indicated that the optimal nutrition and condition requirements for mycelial growth are D-sorbitol, D-(+)-glucose, and D-(-)-fructose as carbon sources; peptone as well as yeast extract and ammonium tartrate as nitrogen sources; and Mn²⁺, Na⁺, and Mg²⁺ as metal ions with pH range from 7.0 to 8.0. Besides, the orthogonal matrix method results revealed that the ideal composition for mycelial growth is 20 g/L D-(-)-fructose, 5 g/L yeast extract, 0.5 g/L Mg²⁺, and pH = 7. We also screened various substrates composition for the activity of lignocellulose-degrading enzymes, i.e., lignin peroxidase, manganese peroxidase, β-glucosidase, a-L-arabinofuranosidase, and laccase. Furthermore, we identified 37 VOCs using GC-MS, and the most striking aspect was the presence of a big series of alcohols and acids, collectively constituted about 49% of the total VOCs. Ergosta-5, 8, 22-trien-3-ol, (3.beta.,22E) was the most plenteous compound constituted 30.369%. This study hopes to establish a better understanding for researchers regarding Termitomyces heimii cultivation on a large scale for the production of lignocellulosic enzymes and some fungal medicine.