Competition and synergistic mechanisms of species in Phyllostachys edulis-Alsophila spinulosa association based on niche theory.

We examined the niche characteristics and interspecific covariant relationship of main species in Phyllostachys edulis-Alsophila spinulosa association in Chishui A. spinulosa National Nature Reserve under P. edulis disturbance condition, and analyzed the mechanism of competition and coexistence across different species. The results showed that there were 67 species from 53 genera and 40 families in the association. The importance values, Shannon niche breadth index (BS), and Levins niche breadth index (BL) of P. edulis were the largest, indicating its absolute dominant status in association. The importance value and BL of A. spinulosa ranked the second, while BS was the third. There were 190 pairs of 20 main species. The niche overlap between P. edulis and A. spinulosa was the largest, with niche overlap value of 0.64. 71.6% of species pairs had niche overlap of less than 0.2, indicating low niche overlap and high degree of niche differentiation among species. The overall association of main species in association was significantly positive, and the community was relatively stable. The correlation among the main species was not significant, the linkage was not strong, and the species were independent from each other. P. edulis showed significant positive correlation with A. spinulosa, Brassaiopsis glomerulata, Ficus virens, and Mallotus barbatus, while P. edulis showed significant negative correlation with Mallotus philippensis, Cinnamomum glanduliferum, and Machilus gamblei. Niche difference and fitness between P. edulis and natives affected the coexistence and competition among species. Controlling the expansion of P. edulis and limiting the size of species with negative correlation with A. spinulosa could create a favorable living environment for A. spinulosa.

Modification of nanoscale polymeric adsorbent for the preparative separation and purification of tacrolimus from fermentation broth of Streptomyces tsukubaensis.

Tacrolimus is an important immunosuppressant produced by microbial fermentation. In this study, a modified nanoscale polymeric adsorbent, Ag+-exchanged resin, was prepared and studied for the preparative separation and purification of tacrolimus from fermentation broth of Streptomyces tsukubaensis. The performance and absorption characteristics of the modified nanoscale polymeric adsorbent namely Ag-NPS was evaluated. Notably, Ag-NPS resin displayed the pronounced separation capacities for tacrolimus and its equilibrium adsorption data was well-fitted to the Langmuir isotherm. Moreover, the dynamic adsorption and desorption tests was carried out to obtain the operational parameters for further purification of tacrolimus. Finally, tacrolimus and the two major impurities, ascomycin and dihydrotacrolimus, were separated well in the scale-up purification process. The purity and recovery of tacrolimus was recorded to be 99.12±0.25% and 90.41±2.05%. In conclusion, this method displayed a high potential for separation and purification of tacrolimus and other unsaturated bioactive compounds in high yield from the fermentation broth.