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• High molecular weight keratin (HMK) was prepared via multi-enzyme cascade pathway. • PHBV/HMK nanofibrous mat showed more favorable mechanical properties. • Silver nanoparticles (AgNPs) were synthesized on nanofibrous mat via keratinase. • PHBV/HMK/AgNPs exhibited effective antibacterial activity and hydrophilicity. • PHBV/HMK/AgNPs showed great biocompatibility and could promote wound healing. Keratin is widely used in the biomaterial application, but the keratin prepared by the physical or chemical approach has relatively low molecular weight and mechanical properties. Here we report the preparation of high molecular keratin (HMK) with molecular weight of 120 kDa via multi-enzyme cascade pathway and its application in wound healing. Briefly, we prepared the soluble keratin from wool by keratinase and improved the molecular weight of keratin by transglutaminase (TGase). The HMK was coelectrospun with poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) and the prepared nanofibrous mats demonstrated improved mechanical properties. Ag nanoparticles (AgNPs) were synthesized on the nanofibers via in situ bioreduction, using the above-mentioned keratinase as the reducing agent. It is demonstrated that the PHBV/HMK/AgNPs nanofibrous mats possess favorable antibacterial properties and good biocompatibility. Moreover, in vivo wound healing assessment, the PHBV/HMK/AgNPs membrane displayed better wound healing ability than the control group. These results indicate that PHBV/HMK/AgNPs mats exhibit significant potential in tissue engineering. [ABSTRACT FROM AUTHOR]

• A promoter screening system of keratinase expression was constructed. • Promoter engineering significantly improved the keratinase activity by 16-fold. • Scale-up fermentation resulted in the highest keratinase activity of 16,860 U/mL. • The keratinase showed potential in biodegradation of feather wastes. Keratinases are promising alternatives over ordinary proteases in several industrial applications due to their unique properties compared with their counterparts in the protease categories. However, their large-scale industrial application is limited by the low expression and poor fermentation efficiency of keratinase. Here, we demonstrate that the expression level of keratinase can be improved by constructing a more efficient enzyme expression system hereby enables the highest production titer as regarding recombinant keratinase production to date. Specially, ten promoters were evaluated and the aprE promoter exhibits a significant promotion of keratinase (kerBv) titer from 165 U/mL to 2605 U/mL in Bacillus subtilis. The batch fermentation mode resulted in a maximum keratinase activity of 7176 U/mL at 36 h in a 5-L fermenter. Furthermore, the extracellular keratinase activity attained up to 16,860 U/mL via fed-batch fermentation within 30 h. The combination of keratinase with l -cysteine brings about 66.4 % degree of degradation of feather. Our work provides a new insight into the development of efficient keratinase fermentation processes with B. subtilis cell factory. [ABSTRACT FROM AUTHOR]

Questions: What are the characteristics of the spatial patterns of soil seed banks (SSBs) at local scales? How does the spatial distribution of SSBs relate to above‐ground vegetation? Location: The piedmont plain of the eastern slope of Gandur mountain, Wuhai, northwestern China. Methods: A plot of 50 m × 50 m square, divided into 100 quadrats (5 m × 5 m) and 100 subquadrats (1 m × 1 m), was prepared to conduct a field survey of vegetation and SSB sampling. We analyzed the spatial pattern of 196 samples at different scales and directions with geostatistical analysis. The relationship between above‐ground vegetation and SSB was quantified by integrating geostatistics, point pattern analysis, and spatial comparison (IGPS). Results: The SSB density in the study area was 404.5 ± 352 seeds·m−2. SSBs of shrub species and herbaceous species Ⅱ (occurring only below‐ground) had a moderate spatial autocorrelation, and their spatial dependence increased with increasing scale. The SSB of herbaceous species Ⅰ (occurring both above‐ground and below‐ground) had great spatial autocorrelation, and its spatial dependence showed an initial decrease and then increased. Furthermore, SSBs showed lower spatial heterogeneity in the prevailing wind direction than in other directions. The spatial patterns of SSBs of shrub species and herbaceous species Ⅰ correlated with shrubs within a specific range, but not with herbs, while the SSB of herbaceous species Ⅱ did not have a spatial relationship with above‐ground vegetation. Conclusion: The spatial pattern of SSBs had scale dependence features, which exhibited clustered distribution at a certain scale, and were significantly correlated with above‐ground shrubs. Therefore, we suggest subsampling larger quadrats with smaller sample units near shrubs in desert areas. Our workflow seems efficient for determining the spatial pattern of SSBs at medium small scale in arid areas. [ABSTRACT FROM AUTHOR]