Rapid green synthesis of silver nanoparticles from Chrysanthemum indicum L and its antibacterial and cytotoxic effects: an in vitro study

Selvaraj Arokiyaraj,1 Mariadhas Valan Arasu,2 Savariar Vincent,3 Nyayirukannaian Udaya Prakash,4 Seong Ho Choi,5 Young-Kyoon Oh,1 Ki Choon Choi,2 Kyoung Hoon Kim1,61Department of Animal Nutrition and Physiology, National Institute of Animal Science, Rural Development Administration, Suwon, Republic of Korea; 2Grassland and Forage Division, National Institute of Animal Science, Rural Development Administration, Seonghwan-Eup, Cheonan-Si, Chungnam, Republic of Korea; 3Center for Environmental Research and Development, Loyola College, Chennai, India; 4Research and Development, Vel Tech Dr RR and Dr SR Technical University, Chennai, India; 5Department of Animal Science, Chungbuk National University, Chungbuk, Republic of Korea; 6Department of Animal Science, Seoul National University, Pyeongchang, Republic of KoreaAbstract: The present work reports a simple, cost-effective, and ecofriendly method for the synthesis of silver nanoparticles (AgNPs) using Chrysanthemum indicum and its antibacterial and cytotoxic effects. The formation of AgNPs was confirmed by color change, and it was further characterized by ultraviolet–visible spectroscopy (435 nm). The phytochemical screening of C. indicum revealed the presence of flavonoids, terpenoids, and glycosides, suggesting that these compounds act as reducing and stabilizing agents. The crystalline nature of the synthesized particles was confirmed by X-ray diffraction, as they exhibited face-centered cubic symmetry. The size and morphology of the particles were characterized by transmission electron microscopy, which showed spherical shapes and sizes that ranged between 37.71–71.99 nm. Energy-dispersive X-ray spectroscopy documented the presence of silver. The antimicrobial effect of the synthesized AgNPs revealed a significant effect against the bacteria Klebsiella pneumonia, Escherichia coli, and Pseudomonas aeruginosa. Additionally, cytotoxic assays showed no toxicity of AgNPs toward 3T3 mouse embryo fibroblast cells (25 µg/mL); hence, these particles were safe to use.Keywords: antibacterial activity, Chrysanthemum indicum, green synthesis, silver nanoparticle, cytotoxi

Production of 3-hydroxypropionic acid from glycerol by acid tolerant Escherichia coli

The biological production of 3-hydroxypropionic acid (3-HP) has attracted significant attention because of its industrial importance. The low titer, yield and productivity, all of which are related directly or indirectly to the toxicity of 3-HP, have limited the commercial production of 3-HP. The aim of this study was to identify and select a 3-HP tolerant Escherichia coli strain among nine strains reported to produce various organic acids efficiently at high titer. When transformed with heterologous glycerol dehydratase, reactivase and aldehyde dehydrogenase, all nine E. coli strains produced 3-HP from glycerol but the level of 3-HP production, protein expression and activities of the important enzymes differed significantly according to the strain. Two E. coli strains, W3110 and W, showed higher levels of growth than the others in the presence of 25 g/L 3-HP. In the glycerol fed-batch bioreactor experiments, the recombinant E. coli W produced a high level of 3-HP at 460 +/- A 10 mM (41.5 +/- A 1.1 g/L) in 48 h with a yield of 31 % and a productivity of 0.86 +/- A 0.05 g/L h. In contrast, the recombinant E. coli W3110 produced only 180 +/- A 8.5 mM 3-HP (15.3 +/- A 0.8 g/L) in 48 h with a yield and productivity of 26 % and 0.36 +/- A 0.02 g/L h, respectively. This shows that the tolerance to and the production of 3-HP differ significantly among the well-known, similar strains of E. coli. The titer and productivity obtained with E. coli W were the highest reported thus far for the biological production of 3-HP from glycerol by E. coli

Glycerol assimilation and production of 1,3-propanediol by Citrobacter amalonaticus Y19

Citrobacter amalonaticus Y19 (Y19) was isolated because of its ability for carbon monoxide-dependent hydrogen production (water-gas shift reaction). This paper reports the assimilation of glycerol and the production of 1,3-propanediol (1,3-PDO) by Y19. Genome sequencing revealed that Y19 contained the genes for the utilization of glycerol and 1,2-propanediol (pdu operon) along with those for the synthesis of coenzyme B-12 (cob operon). On the other hand, it did not possess the genes for the fermentative metabolism of glycerol of Klebsiella pneumoniae, which consists of both the oxidative (dhaD and dhaK) and reductive (dhaB and dhaT) pathways. In shake-flask cultivation under aerobic conditions, Y19 could grow well with glycerol as the sole carbon source and produced 1,3-PDO. The level of 1,3-PDO production was improved when vitamin B-12 was added to the culture medium under aerobic conditions. Under anaerobic conditions, cell growth and 1,3-PDO production on glycerol was also possible, but only when an exogenous electron acceptor, such as nitrate or fumarate, was added. This is the first report of the glycerol metabolism and 1,3-PDO production by C. amalonaticus Y19