Microbial biodegradation potential of hydrocarbons evaluated by colorimetric technique: a case study

The increasing industrial development promotes serious environmental damage due to pollution of the environment. Regarding the petrochemical industry, contamination by oil and its derivatives causes the degradation of terrestrial and aquatic ecosystems. Thus, control and treatment strategies to combat the hazardous effects of oil pollution are needed. However, conventional physical-chemical treatments have high costs and can generate residues that are toxic to the biota. Allying high efficiency and low cost, bioremediation processes represent an extremely important way of recovering contaminated areas among several other cleaning-up techniques. These strategies involve microorganisms and their metabolism in biodegrading organic compounds. Also, the use of nutrients, aeration, pH and temperature adjustments or the addition of substances could make the biodegradation process easier. In order to accomplish this, screening and evaluation methods adapted to a potentially biodegrading microbiota in different types of contaminants have been established. Viable methods in biodegradation data generation during biotechnological process application are fundamental in the elaboration of original references about the biodegradability of certain substances. There are many techniques capable of precisely evaluating biodegradation processes, including colorimetric methods. The isolation, characterization and profile of specific bacteria in petrol derived oil biodegradation capacity studies are important when deciding the correct bioremediation strategy. Different microorganism species have different biodegradation capabilities. Due to this fact, the elaboration of different types of oil biodegradation profiles by different bacteria is an important task for selecting microorganisms in bioremediation processes. In order to accomplish this, screening and evaluation methods adapted to potentially biodegrading bacteria have been established. One of these methods adapted to biodegradation evaluation is colorimetry, which is a technique used to evaluate the biodegradation of some substances. DCPIP based colorimetric technique provides enough data on hydrocarbons used as metabolic substrates by microorganisms. The concentration detection is possible due to the absorbance determination in a specified light specter. The 2,6-dichlorophenol indophenol (DCPIP, redox potential +0.217 V) indicator is widely used in colorimetric processes. Its property is the color change from blue to transparent when subjected to chemical reduction. The indicator, when oxidized is blue and when reduced is transparent. The color change occurs due to a structural change in the molecule, in which the double bond between nitrogen and carbon passes to a simple bond. This insaturation changes the entire molecule, resulting in a macroscopic change in the overall color of the biodegraded substance. The DCPIP indicator is applied in a series of electron transfer reactions, including biodegradable substances. Colorimetric methodology applied to oil biodegradation promotes a better handling of different oil microbial biodegrading profiles. Moreover, such rapid and simple colorimetric methodology provides resources on the development of new techniques in effluent treatments, not only during petrol derived oils, but also on other contaminated organic polymeric compounds.