Relationships with biodegradability

Some quality factors, especially secondary ones, depend directly on material or structural attributes of the product. These product quality factors are often arbitrary and can only be qualitatively evaluated by panels of consumers or experts. Convenience for use, product stability, and ability for human skin protection are all examples of these quality factors. Each arbitrary performance index has specific relationships with the material/structural attributes. In such cases, the desirable quality factor can be realized by directly changing the formulation without concerning any of the performance indices. An example can be that to make a laundry detergent product more convenient to use, the product form can be changed from powder to tablet. Another example is that to make a highly biodegradable product, surfactants with less branching should be used. 

Biodegradable oil spill dispersants with high efficiency and low toxicity have been prepared and tested. They consist of nonionic and low-toxicity surfactants with different molecular weights [2]. The relationship between interfacial tension and the efficiency and chemical structure of the prepared oil spill dispersants was also studied. 

The presence of surfactants and their biodegradation products in different environmental compartments can invoke a negative effect on the biota. The ecotoxicity of surfactants to aquatic life has been summarised in the scientific literature [1—5]. Nevertheless, some information is still lacking in relation to the aquatic toxicity of surfactants, especially knowledge regarding the toxicity of the degradation products, the effect of surfactants on marine species, the ecotoxicity of mixtures of chemical compounds with surfactants, the relationship between toxicity and chemical residue and the effect of surfactant presence in specific environmental compartments (water, particulate matter, pore-water, sediment). 

Although it is still difficult to establish clear cause effect relationships, it is widely accepted that chemical pollution contributes for antibiotic resistance dissemination [10, 33, 34]. There are evidences that antibiotic resistance increase is related with environmental pollution and anthropic pressures. In this respect, antibiotics seem to be a major, although not the unique, form of pollution, mainly because it is estimated that about 75% of the antibiotics consumed by humans and animals are eliminated as active substances [35, 36]. In the environment, antibiotics can suffer adsorption, photolysis or biodegradation, reaching very low concentrations [37]. Nevertheless, at sub-inhibitory levels, as they are found in the environment, antibiotics can promote several alterations on housekeeping functions of the cells. Apparently, some of these alterations are not associated with antibiotic resistance. Even though, they contribute for the perturbation of the microbial community, leading, eventually, to an overall resistance increase [1, 34, 38]. 

Molecular connectivity indices are desirable as potential explanatory variables because they can be calculated for a nominal cost (fractions of a second by computer) and they describe fundamental relationships about chemical structure. That Is, they describe how non-hydrogen atoms of a molecule are "connected". Here we are most concerned with the statistical properties of molecular connectivity Indices for a large set of chemicals In TSCA and the presentation of the results of multivariate analyses using these Indices as explanatory variables to understand several properties important to environmental chemists. We will focus on two properties for which we have a relatively large data base (1) biodegradation as measured by the percentage of theoretical 5-day biochemical oxygen demand (B0D)( 11), and (2) n-octanol/water partition coefficient or hereafter termed log P (12). 

Relationship Between Tm and the Biodegradability of Polyester by Lipases. The relationship between Tm and the biodegradability of saturated aliphatic polyester is shown in Figure 6. For the same series polyesters, the biodegradabilities decreased with increasing Tm. 

An understanding of relationships between cell wall constituents and wall biodegradation is of particular importance to the economics of animal production since low digestibility of forages is associated with reduced intake. Such an understanding is also important in elucidating the role of fiber in human nutrition and of the decomposition of organic matter in soil. 

Each PAH bioremediation strategy has its own unique characteristics. In general, it can be stated that PAH biodegradation will be most rapid and extensive with bioslurry reactors, followed by solid-phase applications and in situ strategies, respectively. Of course there is a direct relationship between rate and extent of PAH biodegradation and cost of the remedial technology. As described below, site-specific criteria impact the applicability of each strategy as well as the predicted performance criteria. 

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