For the enzymatic production of chitosan oligosaccharides from chitosan, a chitosanase-producing bacterium, Bacillus sp. strain KCTC 0377BP, was isolated from soil. The bacterium constitutively produced chitosanase in a culture medium without chitosan as an inducer. The production of chitosanase was increased from 1.2 U/ml in a minimal chitosan medium to 100 U/ml by optimizing the culture conditions. The chitosanase was purified from a culture supernatant by using CM-Toyopearl column chromatography and a Superose 12HR column for fast-performance liquid chromatography and was characterized according to its enzyme properties. The molecular mass of the enzyme was estimated to be 45 kDa by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme demonstrated bifunctional chitosanase-glucanase activities, although it showed very low glucanase activity, with less than 3% of the chitosanase activity. Activity of the enzyme increased with an increase of the degrees of deacetylation (DDA) of the chitosan substrate. However, the enzyme still retained 72% of its relative activity toward the 39% DDA of chitosan, compared with the activity of the 94% DDA of chitosan. The enzyme produced chitosan oligosaccharides from chitosan, ranging mainly from chitotriose to chitooctaose. By controlling the reaction time and by monitoring the reaction products with gel filtration high-performance liquid chromatography, chitosan oligosaccharides with a desired oligosaccharide content and composition were obtained. In addition, the enzyme was efficiently used for the production of low-molecular-weight chitosan and highly acetylated chitosan oligosaccharides. A gene (csn45) encoding chitosanase was cloned, sequenced, and compared with other functionally related genes. The deduced amino acid sequence of csn45 was dissimilar to those of the classical chitosanase belonging to glycoside hydrolase family 46 but was similar to glucanases classified with glycoside hydrolase family 8.Chitosan is currently obtained by the deacetylation of chitin (poly--1,4-D-N-acetylglucosamine) that has been extracted from an abundant source of shrimp or crab shells. Deacetylated chitosans are produced by treating chitin in a concentrated alkaline solution (50%, wt/vol) and boiling it for several hours (34). Chitosan is also found in nature; it is found in the cell walls of fungi of the class Zygomycetes, in the chlorophycean algae Chlorella sp. (26), and in insect cuticles (2). These natural chitosans are synthesized by the tandem action of chitin synthetase and chitin deacetylase, as shown for Mucor rouxii and Colletotrichum lindemuthianum (9). Both chemical and enzymatic procedures for chitosan production result in the incomplete deacetylation of chitin, which yields chitosans in the intermediate range of the degree of deacetylation (DDA). Consequently, chitosan can be considered as a partly deacetylated derivative of chitin; it must have diverse structures containing hetero-linkages of N-acetylglucosamine (GlcNAc)-glucosamine (GlcN) and Gl...
Findings suggest that efforts to promote perceived neighborhood safety and social cohesion are essential to the well-being of older adults. Special attention should be paid to older adults with functional limitations, who appear to be more vulnerable to the negative effects of neighborhood environments.
Background and Objectives
Promoting age-friendliness of communities and supporting aging in place (AIP) are of great importance. Based on processes of belonging and agency, which suggest that person-environment interactions influence residents’ evaluations and behaviors related to the environment, this study aims to examine the interrelationship between the availability of age-friendly features, perceived age-friendliness of community, and intention toward AIP.
Research Design and Methods
This study used the 2015 AARP Age-Friendly Community Survey, which includes 66 home and neighborhood features under the eight domains specified by the WHO’s Age-Friendly Cities Guidelines. A series of regression and mediational analyses were conducted to test hypotheses.
Results
Overall, a greater availability of age-friendly features was positively associated with perceived age-friendliness of community and AIP intention. The relationship between age-friendly features and AIP intention was mediated by perceived age-friendliness of community (50.3% to 96% of the total effects). When perceived age-friendliness of community was introduced to models, the direct effects of housing, outdoor spaces and buildings, and transportation domains remained significant.
Discussion and Implications
Findings suggest that a greater availability of age-friendly features influences older adults’ perception on their community, leading to the development of a desire to age-in-place, supporting processes of belonging and agency. Domains of housing, outdoor spaces and buildings, and transportation may be the most important features in promoting age-friendliness of community and the key determinants of aging in place. Policy makers and practitioners may need to prioritize promoting age-friendly built environment before social environment in building age-friendly communities.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.