Optimization of the fermentation media, mathematical modeling, and enhancement of paclitaxel production by Alternaria alternata after elicitation with pectin.

Alternaria alternata fungus is a potent paclitaxel producer isolated from Corylus avellana. The major challenge is the lack of optimized media for endophytic fungi productivity. In the effort to maximize the production of taxoids by A. alternata, several fermentation conditions, including pH (pH 4.0-7.0), different types and concentrations of carbon (fructose, glucose, sucrose, mannitol, sorbitol, and malt extract), and nitrogen (urea, ammonium nitrate, potassium nitrate, ammonium phosphate, and ammonium sulfate) were applied step by step. Based on the results, A. alternata in a medium containing sucrose 5% (w/v) and ammonium phosphate 2.5 mM at pH 6.0 showed a rapid and sustainable growth rate, the highest paclitaxel yield (94.8 µg gFW-1 vs 2.8 µg gFW-1 in controls), and the maximum content of amino acids. Additionally, the effect of pectin was evaluated on fungus, and mycelia harvested. Pectin significantly enhanced the growth and taxoid yield on day 21 (respectively 171% and 116% of their corresponding on day 7). The results were checked out by mathematical modeling as well. Accordingly, these findings suggest a low-cost, eco-friendly, and easy-to-produce approach with excellent biotechnological potential for the industrial manufacture of taxoids.

Exogenous application of melatonin mitigates the adverse effects of drought stress on morpho-physiological traits and secondary metabolites in Moldavian balm (Dracocephalum moldavica).

Melatonin has emerged as an important signaling molecule that regulates plant responses to environmental stresses. In this research, melatonin was used to alleviate the adverse effects of oxidative stress induced by water deficit in Moldavian balm (Dracocephalum moldavica) plants and morpho-physiological traits were investigated. This experiment was conducted as a factorial arrangement based on completely randomized design with four replications. Treatments included foliar melatonin application at four levels 0 (distilled water), 50, 100 and 150 µM and drought stress 100 (control), 80, 60 and 40% of field capacity (FC). Higher levels of drought stress at 60% and 40% FC, caused the reduction of plant height, shoot fresh and dry weight, root length, root fresh and dry weight, photosynthetic pigments and protein content. Increased amount of soluble sugar content, malondialdehyde content and lipoxygenase activity, non-enzyme antioxidants (including flavonoid, polyphenol compounds and anthocyanin), phenylalanine ammonia-lyase and polyphenol oxidase enzymes activities were also observed at 60% and 40% FC. Melatonin at 100 µM improved morphological parameters, photosynthetic pigments and protein content under moderate and severe drought stress. The obtained results suggested that foliar application of 100 µM melatonin also alleviated oxidative burst and malondialdehyde production in Moldavian balm plant under moderate and severe drought stress probably through regulation of secondary metabolism and the enzymes activity of phenylalanine ammonia-lyase and polyphenol oxidase.