The complete chloroplast genome of Tripsacum laxum (Gramineae).

Tripsacum laxum (Guatemalan grass) is a perennial fodder grasses, which is commonly growing in large parts of Africa for a source of livestock feed. It has a high economic value as a forage. In this study, we obtained a complete chloroplast genome of T. laxum by Illumina sequencing. The results showed a circular genome of 140,556 bp, including the large single copy region (LSC, 82,939 bp), the small single-copy region (SSC, 12,573 bp), and a pair of 22,522 bp inverted repeat regions (IRs). The circular genome contained 120 genes, including 74 protein-coding genes, eight ribosomal RNA genes and 38 tRNA genes. Evolutionary relationship analysis indicates that T. laxum is more closely related to previously reported T. dactyloides.

[Spectroscopic Characterization of DOM During Hyperthermophilic Composting of Sewage Sludge].

Spectroscopy methods such as three-dimensional excitation-emission (3D-EEM) fluorescence spectroscopy were applied to analyze the structures and changes of DOM in hyperthermophilic composting of sewage sludge to fully understand the advantages of hyperthermophilic composting in promoting sludge maturity. The results showed that the temperature reached its peak value at 90℃ and remained over 80℃ for 5 d. The thermophilic period more than 50℃ lasted for 22 d. This indicated that the microorganisms were metabolically active during the composting. The parameters of UV-visible (UV-Vis), including E253/E203, SUVA280, and S275-295, significantly changed from days 0 to 23, showing that the aromaticity degree of DOM and the humification degree of the compost gradually strengthened. Combined with the fluorescence regional integration (FRI), the 3D-EEM analysis results illuminated that the protein-like materials in DOM were completely degraded during days 0 to 6 of the hyperthermophilic composting and a large amount of humic acid-like and fulvic-like materials formed from days 0 to 23, indicating the compost was mature at the hyperthermophilic stage. This was consistent with the germination index (GI) on day 23 (GI=98.5%) as well. Based on the correlation analysis between spectroscopic parameters, PⅤ,n/PⅢ,n showed close relationship with others (r ≥ 0.68), showing their potential as indicators for maturity of hyperthermophilic composting. The results above confirmed that fermentation time could be greatly shortened to about 20 d by using the hyperthermophilic composting, which has great potential for application in organic solid waste management.