The article covers a review of data taken from different publications which are in connection with surface active substances (SAS) generated by microorganisms and their role in biodegradation processes of petroleum pollutants. The structure and properties of selected BSAS were described. The efficiency of hydrocarbons degradation in the presence of synthetic and natural SAS was characterized. The usefulness of biosurfactant for oil pollutants removal from the soil environment was pointed out.
Phytoremediation is a new, promising, quickly developing technique for environmental clean-up. Some plants have the ability to accumulate contaminants by building them into the structure of their own cells, others can collect and metabolize toxins as a result of the natural process of adaptation to difficult life conditions in contaminated environment. The idea of introducing plant systems for environmental cleaning has many advantages, including significantly lower remediation costs compared to traditional methods, convenience of use, favourable effect on soil, and stimulation of the growth of microbial populations. Additionally, the technology is friendly to the environment and improves its aesthetic features.
The vast majority of microorganisms cannot be cultured under laboratory conditions. It was estimated that over 99% of microbial genetic information are inaccessible due to the inability to isolate and culture bacteria. It is also widely known that among those uncultured organisms there are such that bear the genes which are interesting from the biotechnological point of view, i.e. coding for novel enzymes (lipases, amylases, cellulases, polymerases etc.), responsible for resistance to various chemical substances (heavy metals, aromatic compounds, pesticides, antibiotics), or the genes encoding the elements of biosynthetic pathways (for instance producing novel antibiotics). Recently, the methods have been developed that allow (i) isolation and purification of environmental DNA, (ii) construction of random fragment libraries of such DNA, and (iii) effective screening of those libraries in search for interesting genes. These methods are collectively known as ?metagenomics' or ?environmental genomics'. We aim to review the metagenomic methods, which will be done in Part I of our paper, and to present the up ? to ? date achievements and future perspectives for obtaining biotechnologically important genes from environmental samples in Part II. The main attention will be paid to soil metagenomics, as this kind of environment seems to be the most promising in terms of microbial biodiversity and the spectrum of biochemical reactions performed by inhabiting bacteria. We will treat the perspectives for isolation of novel, useful genes such as those coding for biosynthesis of antibiotics, organic compounds degrading pathways, and heavy metal resistance and prospects for their biotechnological application. Assessing the microbial biodiversity through metagenomic methods will also be covered.
Bioremediation of soil contaminated with pesticides g-HCH (lindane), DDT and p,p'-DMDT (methoxychlor) has been studied in batch tests. The treatments included different combinations of the following amendments: carbon source, reducing agent, zero-valent iron, surfactant and anaerobic biomass (methanogenic granular sludge or fermented sewage sludge). The tests seeded with both types of anaerobic biomass showed high removal of all pesticides. DDT was transformed into DDD, but accumulation of this metabolite was considerably lower than that resulting from stoichiometric reaction. Addition of a surfactant together with anaerobic biomass further enhanced the effectiveness of the process.
The common use of heavy metals in several industrial applications has led to their wide distribution in the wastewaters, sediments and soils. Today, due to heavy metals high toxicity and non-biodegradable nature, metal-polluted soils have become one of the serious environmental problems. Remediation technologies developed for metal ? contaminated soil are based on: 1) allowing heavy metals to remain in the polluted site after decreasing their availability by solidification / stabilization processes, or 2) removing heavy metals from soil by e.g. phytoremediation or soil extraction (flushing/washing). Techniques such as ex situ soil washing and in situ soil flushing transfer heavy metals to liquid phase by desorption and solubilization. To support heavy metals' removal from soil matrix, the washing water used in these methods is usually augmented with acids, bases, chelating agents or surfactants. Biosurfactants, surface-active agents of biological origin, produced mainly by microorganisms, have gained considerable interest in environment remediation techniques due to some distinct advantages over the synthetic counterparts such as lower toxicity, higher biodegradability and high selectivity. This paper provides an overview of the application of biosurfactants for the remediation of heavy metal-contaminated soil. Promising alternative surfactant foam technology is described, too.
Extensive industrial and agricultural development of the 20th century is one of the causes of wide-spread contamination of the environment by organic pollutants such as polyaromatic hydrocarbons, pesticides and explosive compounds. Nowadays, apart from traditional remediation techniques involving mechanical treatment, we are facing new opportunities of utilizing microorganisms (bioremediation) and plants (phytoremediation) to contain, transform or remove toxic elements present in soils, water and, to some point, in atmosphere. Great diversity of living organisms and application of genetic engineering make bio- and phytoremediation even more attractive.
Phenol monooxygenase, isolated from Stenotrophomonas maltophilia strain KB2, was sensitive to sodium azide, metals salts except for iron (II) sulfate at concentration of 1 mM, chelate compounds, sulfhydryl agents, lauroylsarcosine Na-salt, SDS and hydrogen peroxide. Slight increase of the enzyme activity was observed in the presence of hexane and ether. The presence of ascorbic acid caused an increase of the enzyme activity. Phenol monooxygenase activity changed significantly depending on the tested aromatic substrate in the reaction mixture and the type of the applied inductor.
Bacteria from Ochrobactrum genus are found in various environments. They were isolated from soil, sewage, plant tissue and human body, where they acted as a human opportunistic pathogens. Ochrobactrum are able to degrade a wide variety of chemical substances, such as atrazine, nicotine, phenol or polycyclic aromatic hydrocarbons (PAH) and accumulate heavy metals. Many of those substances pose a threat to the environment and to mankind. The representatives of this genus also play an important role in the nitrogen cycle as one of the symbiotic bacteria of legume plants that reduce nitrites to atmospheric nitrogen. There is still little information about the genus Ochrobactrum and this is why it is necessary to focus more attention on it in terms of environmental protection.
The family of keratins comprises fibrous proteins of high mechanical and chemical stability, present in skin appendages like feathers, horn, hoof or hair, as well as cytokeratins forming a part of cytoskeleton of epithelial cells. The ability of keratin degradation is a feature of many saprophytic and pathogenic microorganisms, including bacteria, fungi and streptomyces. That also occurs during caspase-mediated apoptotic processes in vertebrate cells. The mechanism of microbial keratinolysis involves action of mainly alkaline serine proteases, but additional processes like sulphitolysis or mechanical breakdown are also known. Among a wide variety of microbes, bacteria, especially from the genus Bacillus, are of interest in terms of large scale biodegradation of keratinic wastes. Diverse applications, including poultry industry or farm wastes digestion, fertilizer composts production, broiler diets supplementation and prion protein decomposition, are mentioned.
Bioremediation is a process by which microoorganisms degrade or transform the environmental contaminants into less toxic forms. A wide variety of bacterial and fungal genera are known to be capable of degrading, and in many cases, completely mineralizing chemical substances present in petroleum products at present. Three types of bioremediation are predominant in the industry: natural attenuation, biostimulation and bioaugmentation. Selecting the most appropriate strategy to treat a specific site can be quided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products, the accessibility of contaminant to microorganisms (bioavailabilty) and the opportunity for optimization of biological activity. Microbial activity is affected by a range of environmental factors, including nutrients, moisture content, pH, temperature, and oxygen concentration. Different aspects of bacterial degradation of petroleum contaminants in soil and how to improve the efficiency and reproducibility are discussed in this review.
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