Production of ultra-high-molecular-weight poly-γ-glutamic acid by a newly isolated Bacillus subtilis strain and genomic and transcriptomic analyses.

Poly-γ-glutamic acid (γ-PGA) is a microbial-derived polymer with molecular weight (Mw) from 104 to 107 Da, and the high-Mw (> 7.0 × 105 Da) or ultra-high-Mw (> 5.0 × 106 Da) γ-PGA has important application value as a tissue engineering material, as a flocculant, and as a heavy metal remover. Therefore, how to produce these high-Mw γ-PGAs with low cost and high efficiency has attracted wide attention. In this study, a γ-PGA producer was isolated from the natural environment, and identified and named Bacillus subtilis GXD-20. Then, the ultra-high-Mw (> 6.0 × 106 Da) γ-PGA produced by GXD-20 was characterized. Interestingly, GXD-20 could produce γ-PGA at 42°C, and exhibited a γ-PGA titer of up to 22.29 ± 0.59 g L-1 in a 5-L fermenter after optimization of the fermentation process. Comparative genomic analysis indicated that the specific protein sequence and subcellular localization of PgdS (a γ-PGA-degrading enzyme) were closely related to the ultra-high-Mw of γ-PGA. Transcriptomic analysis revealed that the high γ-PGA titer at 42°C was mainly related to the high expression of genes encoding enzymes for sucrose transportation and utilization, nitrogen transportation, endogenous glutamate synthesis, and γ-PGA synthesis. These results provide new insights into the production of ultra-high-Mw γ-PGA by Bacillus at high temperatures.

Efficient soluble deep blue electroluminescent dianthracenylphenylene emitters with CIE y (y ≤ 0.08) based on triplet-triplet annihilation.

It has been challenging to develop deep blue organic molecular fluorescent emitters with CIE y (y ≤ 0.08) based on triplet-triplet annihilation (TTA). Here, we report facilely available dianthracenylphenylene-based emitters, which have a 3,5-di(4-t-butylphenyl)phenyl moiety at the one end and 4-cyanophenyl or 3-pyridyl at the other end, respectively. Both fluorophores show a high glass transition temperature of over 220 °C with a thermal decomposition temperature of over 430 °C at an initial weight loss of 1%. The preliminary characterizations of the organic light-emitting diodes (OLEDs) that utilized these nondoped emitters provided high EQEs of 4.6%-5.9% with CIE coordinates (0.15, 0.07-0.08). The analysis of the EL transient decay revealed that TTA contributed to the observed performance. The results show that the new emitters are attractive as a potential TTA-based host to afford stable deep blue fluorescent OLEDs.