Evaluation of Congo red dye decolorization and degradation potential of an endophyte Colletotrichum gloeosporioides isolated from Thevetia peruviana (Pers.) K. Schum.

Decolorization and degradation of textile dye by endophytic fungi stand to be a profitable and viable alternative over conventional methods with respect to eco-friendliness, cost-effectiveness, and non-hazardous nature. One of the active fungal endophytes Colletotrichum gloeosporioides isolated from plant Thevetia peruviana (Pers.) K. Schum. was screened for laccase production and Congo red dye decolorization. Various physicochemical parameters like dye concentration, carbon sources, nitrogen sources, temperature, and pH were optimized, and the maximum decolorization (%) was achieved at 100 mg/L of dye concentration (82%), yeast extract (80%), 30 °C temp (80%), glucose (79%), and 7 pH (78%), respectively. SEM image and fungal biomass changes represent that fungus actively participated in the dye decolorization and had less significant effect on biomass. The regenerative ability of fungus C. gloeosporioides after dye decolorization indicated tolerance against the dye and was found to be more advantageous over previous reports of dye decolorization by other endophytic fungi. UV-Vis spectra, TLC, FTIR, and HPLC results confirmed the decolorization and degradation process due to absorption and biodegradation. Phytotoxicity assay depicted that degraded products are less toxic to Phaseolus mungo compared to Congo red. The overall findings showed that C. gloeosporioides possesses a good decolorization and degradation potential against Congo red and this endophyte can be profitably used for dye-containing wastewater treatment.

Crystal structure and specific location of a germin-like protein with proteolytic activity from Thevetia peruviana.

Peruvianin-I is a cysteine peptidase (EC 3.4.22) purified from Thevetia peruviana. Previous studies have shown that it is the only germin-like protein (GLP) with proteolytic activity described so far. In this work, the X-ray crystal structure of peruvianin-I was determined to a resolution of 2.15 Å (PDB accession number: 6ORM) and its specific location was evaluated by different assays. Its overall structure shows an arrangement composed of a homohexamer (a trimer of dimers) where each monomer exhibits a typical ß-barrel fold and two glycosylation sites (Asn55 and Asn144). Analysis of its active site confirmed the absence of essential amino acids for typical oxalate oxidase activity of GLPs. Details of the active site and molecular docking results, using a specific cysteine peptidase inhibitor (iodoacetamide), were used to discuss a plausible mechanism for proteolytic activity of peruvianin-I. Histological analyses showed that T. peruviana has articulated anastomosing laticifers, i.e., rows of cells which merge to form continuous tubes throughout its green organs. Moreover, peruvianin-I was detected exclusively in the latex. Because latex peptidases have been described as defensive molecules against insects, we hypothesize that peruvianin-I contributes to protect T. peruviana plants against herbivory.

Structured model and parameter estimation in plant cell cultures of Thevetia peruviana.

In this work, a mechanistic model for predicting the dynamic behavior of extracellular and intracellular nutrients, biomass production, and the main metabolites involved in the central carbon metabolism in plant cell cultures of Thevetia peruviana is presented. The proposed model is the first mechanistic model implemented for plant cell cultures of this species, and includes 28 metabolites, 33 metabolic reactions, and 61 parameters. Given the over-parametrization of the model, its nonlinear nature and the strong correlation among the effects of the parameters, a parameter estimation routine based on identifiability analysis was implemented. This routine reduces the parameter's search space by selecting the most sensitive and linearly independent parameters. Results have shown that only 19 parameters are identifiable. Finally, the model was used for analyzing the fluxes distribution in plant cell cultures of T. peruviana. This analysis shows high uptake of phosphates and parallel uptake of glucose and fructose. Furthermore, it has pointed out the main central carbon metabolism routes for promoting biomass production in this cell culture.

Effect of light wavelength on cell growth, content of phenolic compounds and antioxidant activity in cell suspension cultures of Thevetia peruviana.

Thevetia peruviana (T. peruviana) has been considered as a potentially important plant for industrial and pharmacological application. Among the number of compounds which are produced by T. peruviana, antioxidants and polyphenols are of particular interest due to their benefits on human health. Cell suspension cultures of T. peruviana were established under different conditions: 1) constant illumination (24h/day) at different light wavelengths (red, green, blue, yellow and white), 2) darkness and 3) control (12h/12h: day light/dark) to investigate their biomass, substrate uptake, polyphenols production and oxidizing activity. The results showed biomass concentrations between 17.1g dry weight (DW)/l (green light) and 18.2g DW/l (control) after 13days. The cultures that grew under green light conditions consumed completely all substrates after 10days, while other cultures required at least 13days or more. The total phenolic content was between 7.21 and 9.46mg gallic acid (GA)/g DW for all light conditions. In addition the ferric reducing antioxidant power and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid antioxidant activity ranged from 5.41-6.58mg ascorbic acid (AA)/g DW and 82.93-110.39µmol Trolox/g DW, respectively. Interestingly, the samples which grew under the darkness presented a higher phenolic content and antioxidant capacity when compared to the light conditions. All together, these results demonstrate the extraordinary effect of different lighting conditions on polyphenols production and antioxidant compounds by T. peruviana.