The change of water content and role of microbe in the sludge drying process

Time-dependent effects of microplastics on soil bacteriome

Microplastic threats to biodiversity, health and ecological safety are adding to concern worldwide, but the real impacts on the functioning of organisms and ecosystems are obscure owing to their inert characteristics. Here we investigated the long-lasting ecological effects of six prevalent microplastic types: polyethylene (PE), polypropylene (PP), polyamide (PA), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) on soil bacteria at a 2 % (w/w) level. Due to the inertia and lack of available nitrogen of these microplastics, their effects on bacteriome tended to converge after one year and were strongly different from their short-term effects. The soil volumes around microplastics were very specific, in which the microplastic-adapted bacteria (e.g., some genera in Actinobacteria) were enriched but the phyla Bacteroidetes and Gemmatimonadetes declined, resulting in higher microbial nitrogen requirements and reduced organic carbon mineralization. The reshaped bacteriome was specialized in the genetic potential of xenobiotic and lipid metabolism as well as related oxidation, esterification, and hydrolysis processes, but excessive oxidative damage resulted in severe weakness in community genetic information processing. According to model predictions, microplastic effects are indirectly derived from nutrients and oxidative stress, and the effects on bacterial functions are stronger than on structure, posing a heavy risk to soil ecosystems.

Dynamic changes of microbial community and moisture ratio during bio-drying of sludge after electro-dewatering

Using electro-dewatering as the pretreatment process for sludge bio-drying can improve the dewatering performance. It was innovatively investigated including the microbial mechanism and the kinetics of moisture removal by bio-drying with electro-dewatered sludge in this study. Two bio-drying processes using electro-dewatered sludge (EDS) and sludge added cornstalk conditioner (CSS) were compared. Microbial community analysis showed that the abundance of Bacteroidetes increased from 4.21% to 16.67% after electro-dewatering. The dominant phyla were Bacteroidetes (36.79%), Proteobacteria (32.35%), and Actinobacteria (24.58%) at the end of EDS bio-drying. Network analysis revealed that the co-occurrence patterns in EDS included 40 nodes and 97 edges. The prediction results of the Kyoto Encyclopedia of Genes and Genomes demonstrated that the relative abundances of carbohydrate metabolism and metabolism of terpenoids and polyketides in sludge decreased, while the relative abundances of lipid metabolism, xenobiotic biodegradation and metabolism increased after electro-dewatering. Five thin layer drying kinetic models were analyzed to estimate the bio-drying kinetic parameters. The Page's model could be better fitted to the results and the highest R² was 0.9570 in the EDS. The new coefficients k (0.1637) and n (1.2097) were obtained. The results provided mechanism and data support for exploring and applying bio-drying technology after sludge electro-dewatering.

Dynamic Changes in Endophytic Microorganisms and Metabolites During Natural Drying of Licorice

The method of drying licorice is an important factor affecting the quality of the final product. To determine the best processing method of licorice postharvest, we investigated the interaction of increasing aridity between the endophytic microorganisms and the accumulation of metabolites. Samples from the roots of licorice growing along an aridity gradient during the natural drying process were collected, and the metabolic components, the content of the main active substances and the dynamic changes of the endophytic microbial community were assessed. The glycyrrhizic acid and liquiritin contents decreased slightly or remained flat during natural drying, whereas those of liquiritigenin and isoliquiritigenin increased slightly. Moreover, the Shannon index of endophytic microbial diversity of licorice was the highest in the fresh period and showed a downward trend during the drying process. When the licorice were fresh, Cladosporiaceae and Burkholderiaceae were the dominant family present, but after drying, Nectriaceae and Enterobacteriaceae were the dominant families. A similar trend was also found in which the differential metabolites of licorice were reduced during natural drying. Furthermore, correlation analysis between dominant families and differential metabolites showed that there was a correlation between the two. Therefore, fresh processing is an effective drying method to ensure the quality of licorice. This study revealed the relationship of endophytic microbiota and changes in the licorice metabolites during different stages of drying, which provided a scientific basis for the drying method of licorice.