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3, 5, 6-trichloro-2-pyridinol (TCP) is a widespread organic pollutant with persistent, mobile and high antimicrobial effects. Here, nanoFe3O4 was firstly introduced into the anoxic biodegradation of TCP. It was found that nanoFe3O4 significantly accelerated TCP biodegradation. The removal rate of TCP (100 mg L−1) increased from 83.03% to 98.74% within 12 h in the presence of nanoFe3O4, and the addition of nanoFe3O4 also promoted the accumulation of CO2. Reductive dechlorination mechanism was involved in anoxic biodegradation of TCP. Molecular approaches further revealed that nanoFe3O4 distinctly induced the shifts of bacterial community. The dominant genus Ochrobactrum was converted to genus Delftia in nanoFe3O4 treatment, and the relative abundance of Delftia increased from 10.26% to 44.62%. Meanwhile, the total relative abundance of bacteria related to TCP dechlorination and degradation significantly increased in the presence of nanoFe3O4. These results indicated that nanoFe3O4 induced the enrichment of TCP-degrading bacteria to promote the anoxic biodegradation of TCP.

As a natural sweetening and solubilizing agent, rubusoside has great potential in the application of healthy beverages and pharmaceuticals. However, the direct extraction and purification of rubusoside from raw materials is inefficient. In this work, a novel β-glucosidase (CsBGL) was obtained from Chryseobacterium scophthalmum 1433 through screening of the environmental microorganisms. CsBGL markedly hydrolyzed sophorese (Glcβ1-2Glc) and laminaribiose (Glcβ1-3Glc), but for steviol glycosides, it only hydrolyzed the C-13/C-19-linked sophorese, instead of the C-13/C-19-linked Glcβ1-2[Glcβ1-3]Glc trisaccharide and Glcβ1-monosaccharide. It efficiently hydrolyzed stevioside (240 g/L) to produce rubusoside (99% yield) at 47.5°C for 70 min. Even when using a crude steviol glycosides extract (500 g/L) containing ∼226 g/L stevioside as the substrate, CsBGL could also convert stevioside to rubusoside (99% yield) at 47.5°C for 2 h, in which the rubusoside concentration increased from the initial 42 g/L to the final 222 g/L. These results reveal that CsBGL would be a promising biocatalyst for the industry-scale production of rubusoside from stevioside or/and the crude steviol glycosides extract.

Biodegradation of 3,5,6-trichloro-2-pyridinol (TCP) in drylands is an important biological process of detoxification. Flooding in drylands can result in the formation of anaerobic habitats. However, little is known about the microbial metabolism of TCP in dryland soil under anaerobic conditions. Here, chlorpyrifos-contaminated dryland soil was incubated to enrich the TCP-degrading microbial consortium under anaerobic conditions. Chloridion and CO2 were released with TCP degradation, and the enrichment cultures of dryland soil could metabolize 97% of TCP (100 mg/L) within 20 h. Both reductive and hydrolysis dechlorination mechanisms were involved in TCP biodegradation under anaerobic conditions. Bacterial taxonomic analysis revealed that the aerobic TCP-degrading bacteria Ochrobactrum and dechlorination bacteria Delftia were the dominant genera. Anaerobic and facultative bacteria; i.e., Bacteroides, Bacillus, and Cupriavidus had lower relative abundances, but they were significantly enriched following treatment with TCP. These results indicate that the enrichment cultures of dryland soil dominated by aerobic bacteria could dechlorinate and degrade TCP under anaerobic conditions.

The effect of particle size on the transformation kinetics of flue gas desulfurization (FGD) gypsum to α-calcium sulfate hemihydrate (α-HH) in calcium chloride (CaCl2) solutions was investigated to better guide value-added FGD gypsum use. Gypsum samples from different sources were sieved into several size groups, and their transformation rates were compared. The results showed that using FGD gypsum with a smaller particle size accelerated the transformation to α-HH. The size effect accelerated nucleation kinetics of α-HH rather than its crystal growth rate (that is, the thermodynamic driving force for the transformation changed little with particle size variation). Analysis using a kinetics model revealed that a smaller gypsum particle size lowered the overall activation energy barrier for the transformation. This is because the smaller gypsum particles had a larger relative specific surface area and thus provided more nucleation sites and crystalline defects to promote α-HH nucleation. A smaller particle size of FGD gypsum also gave a higher yield of fine α-HH particles because of the increased incidence of primary and secondary nucleation coupled with attrition. This paper indicates the transformation of FGD gypsum into α-HH could be effectively promoted by regulating FGD gypsum particle size.