Aerobic Biodegradation of Phenols: A Comprehensive Review

Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.

Within the frame of the sustainable development, new materials are being conceived in order to increase their biodegradability properties. Biodegradation is considered to take place throughout three stages: biodeterioration, biofragmentation and assimilation, without neglect the participation of abiotic factors. However, most of the techniques used by researchers in this area are inadequate to provide evidence of the final stage: assimilation. In this review, we describe the different stages of biodegradation and we state several techniques used by some authors working in this domain. Validate assimilation (including mineralisation) is an important aspect to guarantee the real biodegradability of items of consumption (in particular friendly environmental new materials). The aim of this review is to emphasise the importance of measure as well as possible, the last stage of the biodegradation, in order to certify the integration of new materials into the biogeochemical cycles. Finally, we give a perspective to use the natural labelling of stable isotopes in the environment, by means of a new methodology based on the isotopic fractionation to validate assimilation by microorganisms.

Cyanides are produced by certain bacteria, fungi, and algae, and may be found in plants and some foods, such as lima beans and almonds. Although cyanides are present in small concentrations in these plants and microorganisms, their large-scale presence in the environment is attributed to the human activities as cyanide compounds are extensively used in industries. Bulk of cyanide occurrence in environment is mainly due to metal finishing and mining industries. Although cyanide can be removed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. From an economic standpoint, the biological treatment method is cost-effective as compared to chemical and physical methods for cyanide removal. Several microbial species can effectively degrade cyanide into less toxic products. During metabolism, they use cyanide as a nitrogen and carbon source converting it to ammonia and carbonate, if appropriate conditions are maintained. Biological treatment of cyanide under anaerobic as well as aerobic conditions is possible. The present review describes the mechanism and advances in the use of biological treatment for the removal of cyanide compounds and its advantages over other treatment processes. It also includes various microbial pathways for their removal.