Using drug-loaded pH-responsive poly(4-vinylpyridine) microspheres as a new strategy for intelligent controlling of Lactobacillus plantarum contamination in bioethanol fermentation.

Bioethanol fermentation is usually contaminated by bacteria, especially lactic acid bacteria (LAB), thereby leading to decrease of bioethanol yield and serious economic losses. Nisin is safer for controlling of bacterial contamination than antibiotics that are widely applied in industry. Moreover, in LAB contaminative bioethanol fermentation system, consistently decreased pH value provides opportunity to realize pH value responsive material-based release of anti-bacteria substances for intelligent and persistent controlling of bacterial contamination. In this study, nisin was embedded into pH-sensitive poly(4-vinylpyridine) (P4VP) microspheres synthesized by suspension polymerization to realize intelligent controlling of Lactobacillus plantarum contamination in bioethanol fermentation. Chloramphenicol with the highest antimicrobial activity and excellent stability was chosen as the model drug to be embedded into P4VP microspheres to test the drug release behavior. The drug release curve of chloramphenicol-loaded P4VP microspheres showed sustained and pH-responsive release properties. The diameters of the microspheres ranged from 40 to 100 µm. The encapsulation efficiency of nisin into P4VP microspheres was 47.67% and the drug-loading capacity of nisin was 2.5%. Nisin-loaded P4VP microspheres were added into the simulated contaminative fermentation system, and successfully reversed the decline of bioethanol yield secondary to L. plantarum contamination. The results in this study indicated that L. plantarum contamination in bioethanol fermentation could be effectively controlled by nisin-loaded P4VP microspheres.

Urban expansion dynamic and its potential effects on dry-wet circumstances in China's national-level agricultural districts.

Although urbanization has been widely examined in individual city and urban agglomeration scales, urban expansion patterns and dynamics in large-scale agricultural districts remain absent. In this study, multifaceted characteristics in urban expansion were quantified in China's nine national-level agricultural districts, and responses of dry-wet circumstances to urban sprawl were evaluated. From 1980 to 2018, China has undergone an extensive urban sprawl. Huang-Huai-Hai Plain (HHHP) has the maximum urban coverage extent, followed by Middle-lower Yangtze Plain (MLYP) and Southern China (SC). The largest annual increase was recorded in MLYP, reaching 816.12 km2; followed by HHHP, with an annual increase of 725.22 km2. There are prominent heterogeneities in expansion rate and direction among various districts. The dominating growth patterns were edge- and leapfrogging-expansion, accompanying by a less percentage of infilling-expansion. Accompanying by urbanization, connectedness in urban landscapes gradually improved, while separation degree decreased. Upon many occasions, holistic average dry-wet circumstances in non-urbanized areas are superior to those in urban areas, although this is not absolute for all the districts or periods. In urbanization progress, the development of leapfrogging-expansion has a potential to ameliorate dry-wet circumstances in both urban and non-urban zones, while infilling- and edge-expansion would constitute an inverse effect. In comparison to urban zones, leapfrogging-expansion would cause a more prominent effect on dry-wet environment in non-urbanized zones. Increased connectivity in urbanized landscapes would improve dry-wet environments, especially for urbanized zones. Inversely, increased spatial separated extent among urban landscapes would perform an opposite effect. This study provides a potential for understanding the dynamic features of urban expansion in large-scale agricultural districts. Moreover, the results can also provide a potential opportunity for optimizing dry-wet environments by regulating urbanization pattern and landscape configuration.