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Polyphenols and flavonoids are abundant in spent onion skins (SOSs), being present in amounts are 2–sixfold greater times of than those in the inner bulb. In this study, an eco-friendly and efficient extraction method based on temperature-responsive deep eutectic solvents (TRDESs) was used to obtain natural flavonoids from SOSs. Microwave-assisted extraction yields of quercetin, kaempferol, luteolin, and quercetin-3-O-β-D-glucoside were evaluated to determine the efficiencies of a series of TRDESs. An extraction system composed of ethanolamine and m-cresol at ratio of 1:1 (20% water in TRDES system) was found to possess the highest efficiency. The extraction conditions were screened and optimized for efficiency using a Box-Behnken design. As a result, an extraction power of 554 W, extraction temperature of 76 °C, extraction time of 16 min, and solid–liquid ratio of 14 mg/mL were determined to be the optimal conditions. Under these extraction conditions, the total flavonoid extraction yields reached 47.83 ± 0.21 mg/g. The macroporous resin HPD 600 was selected for the separation and recovery of the TRDESs extraction mixture and the experimental measurements revealed that it allowed recovery rate more than 90%. In vitro activity testing of the flavonoid extract demonstrated excellent FRAP assay, DPPH assay and ABTS assay results for the SOSs extract prepared using a TRDES, and its inhibitory effects on S. aureus, E. carotovora, and B. subtilis were marked. [ABSTRACT FROM AUTHOR]

A Gram-negative, ellipsoidal to short-rod-shaped, motile bacterium was isolated from Beijing's urban air. The isolate exhibited the closest kinship with Noviherbaspirillum aerium 122213-3 T , exhibiting 98.4 % 16S rRNA gene sequence similarity. Phylogenetic analyses based on 16S rRNA gene sequences and genomes showed that it clustered closely with N. aerium 122213-3 T , thus forming a distinct phylogenetic lineage within the genus Noviherbaspirillum . The average nucleotide identity and digital DNA-DNA hybridization values between strain I16B-00201 T and N. aerium 122213-3 T were 84.6 and 29.4 %, respectively. The respiratory ubiquinone was ubiquinone 8. The major fatty acids (>10 %) were summed feature 3 (C 16:1 ω6 c /C 16:1 ω7 c , 43.3 %), summed feature 8 (C 18:1 ω7 c /C 18:1 ω6 c , 15.9 %) and C 12:0 (11.0 %). The polyamine profile showed putrescine as the predominant compound. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, unknown lipids and unknown phosphatidylaminolipids. The phenotypic, phylogenetic and chemotaxonomic results consistently supported that strain I16B-00201 T represented a novel species of the genus Noviherbaspirillum , for which the name Noviherbaspirillum album sp. nov. is proposed, with I16B-00201 T (=CPCC 100848 T =KCTC 52095 T ) designated as the type strain. Its DNA G+C content is 59.4 mol%. Pan-genome analysis indicated that some Noviherbaspirillum species possess diverse nitrogen and aromatic compound metabolism pathways, suggesting their potential value in pollutant treatment.