Environmental Biotechnology: Biotechnological Methods Monitoring Pollutants

INTRODUCTION

In the world today, the demand for the use of sustainable and eco-friendly environmental processes is rapidly growing, subjected to economic, public, and legislation pressure. Biotechnology provides a pool of opportunities for effectively addressing issues pertaining to the monitoring, assessment, and treatment of contaminated water, air, and solid waste streams. These pollutants in the environment are great risks for the health of human beings. In this context, source tracking of environmental pollutants and its treatment using biological-based methods is becoming increasingly important, mainly, owing to the accuracy and robustness of such techniques. Thus comes Biomonitoring, which involves the use of organisms to assess environmental contamination, such as of surrounding air or water. This can be done qualitatively by observing and noting changes in organisms, or quantitatively by measuring accumulation of chemicals in organism tissues.

By observing or measuring the effects the environment has on its resident organisms, pollution may be suspected or inferred. Here, biomonitoring is associated with remote sensors where remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation, especially the Earth. Remote sensing is used in numerous fields, including geography, land surveying and most Earth science disciplines (for example, hydrology, ecology, meteorology, oceanography, glaciology, geology); it also has military, intelligence, commercial, economic, planning, and humanitarian applications.

BIOTECHNOLOGICAL REMOTE SENSORS - Measuring Pollutants

The different biotechniques available nowadays, represent both well-established as well as novel (bio) technologies, although several aspects of their performance are still to be tested, for instance, the use of novel biocatalysts and reactor designs, the understanding of the microbial community dynamics as well as the mechanisms occurring within a bioreactor, and the assessment of the performance and efficiency of bioreactors during long-term operation. If these mechanisms are well understood, biotechniques will potentially help change the way manufacturers and users build and rebuild technologies for the sustainable use of different biological processes for wastewater, air, and solid waste release and their treatments.

Thereby, measuring pollutants can be done with the help on various old and newly developed biotechnological remote sensors or biosensors etc some of which are discussed below:

• Monitoring pollutants can also be done by determining the effect of pollutants in the environment as BOD and COD analysis doesn't always determine the effect of pollution on organism. Thus the use of specific Bioindicators and Biomarkers can be done for such.

1. Bioindicators: measure the effect of pollutants on whole organism representative of the environment and thereby help monitor pollutants.
2. Biomarkers: on the other hand measure the effect of pollutants on physiological, biochemical and molecular characteristics of organism in the environment for such.

• Microextraction - Solid-phase microextraction (SPME), is a solid phase extraction technique that involves the use of a fiber coated with an extracting phase, that can be a liquid (polymer) or a solid (sorbent), which extracts different kinds of analytes (including both volatile and non-volatile) from different kinds of media, that can be in liquid or gas phase. The quantity of analyte extracted by the fibre is proportional to its concentration in the sample as long as equilibrium is reached or, in case of short time pre-equilibrium, with help of convection or agitation.
• Electrochemical biosensors and the development of new biosensors contribute to the environmental pollutants monitoring. Electrochemical biosensors offer precision, sensitivity, rapidity, and ease of operation for on-site environmental analysis. An electrochemical biosensor is an analytical device in which a specific biological recognition element (bioreceptor) is integrated within or intimately associated with an electrode (transducer) that converts the recognition event to a measurable electrical signal for the purpose of detecting a target compound (analyte) in solution. This approach not only provides the means for on-site analysis but also removes the time delay and sample alteration that can occur during transport to a centralized laboratory.
• Microbial biosensors - Using biological engineering researchers have created many microbial biosensors. A microbial biosensor is a biosensor that uses microorganisms which consists of numerous enzymes as the bioelements. The enzymes in the living cells can produce a response to the analytes specifically and selectively, without neither the necessity of time-consuming and costly purification nor the negative effects of the operating environment. Some examples include:

Bioluminescence based microbial biosensors have been extensively used in environmental monitoring for detection of toxicity due to its ability to closely reflect to toxicity. As a proportional response to the concentration of the analytes, the changes in the density of the bioluminescence emitted by the living cells can be measured by the bioluminescent microbial biosensor. According to the mechanism of production of bioluminescence, the method to control the expression of the lux gene can be divided into two manners: the constitutive manner and the inducible manner. The constitutive manner (light-off) and the inducible manner (light-on) are two general strategies for developing a microbial biosensor for monitoring heavy metal toxicity. In the constitutive manner, the lux gene exists constitutively.

Arsenic biosensor: To detect arsenic they use the Ars operon. Using bacteria, researchers can detect pollutants in samples. In molecular biology, the ars operon is an operon found in several bacterial taxon. It is required for the detoxification of arsenate, arsenite, and antimonite. This system transports arsenite and antimonite out of the cell. The pump is composed of two polypeptides, the products of the arsA and arsB genes. This two-subunit enzyme produces resistance to arsenite and antimonite. Arsenate, however, must first be reduced to arsenite before it is extruded. A third gene, arsC, expands the substrate specificity to allow for arsenate pumping and resistance. ArsC is an approximately 150-residue arsenate reductase that uses reduced glutathione (GSH) to convert arsenate to arsenite with a redox active cysteine residue in the active site. ArsC forms an active quaternary complex with GSH, arsenate, and glutaredoxin 1 (Grx1). The three ligands must be present simultaneously for reduction to occur.

EXAMPLES – Relating to Air, Water (Marine), Soil Pollutants

Owing to the emerging globalization, industrialization, increase in the population in the planet leading to Global Diaspora, tremendous increase in the amount and types of pollutants in air, water and soil is much contributed. Here comes the use of the various biomontoring remote sensors to monitor pollutants which is of supreme importance that helps in the developments of various treatments, preventive and degradation methods that are ought to solve the rising pollution problems. Some examples are cited below:

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Air pollutants are atmospheric substances both naturally occurring and anthropogenic which may potentially have a negative impact on the environment and organism health. With the evolution of new chemicals and industrial processes has come the introduction or elevation of pollutants in the atmosphere, as well as environmental research and regulations, increasing the demand for air quality monitoring.

Air pollution can thus be assessed by biomonitoring with organisms that bioaccumulate air pollutants, such as lichens, mosses, fungi, and other biomass. One of the benefits of this type of sampling is that how quantitative information can be obtained via measurements of accumulated compounds, representative of the environment from which they came from. However, careful considerations must be made while choosing the particular organism, how it's dispersed, and relevance to the pollutant.

Other sampling methods include the use of a denuder, needle trap devices, and microextraction techniques.

Water and Marine Pollutants - Increased levels of marine pollution due to anthropogenic activities are adversely affecting marine sustainability of marine ecosystems. These include oil and chemical spills, sewage, high suspended solids, and algal blooms.

1. Heavy metal pollution in coastal and estuarine region is another major concern of marine managers and researchers. Being extensively used in industry, heavy metal becomes a main toxicant in waste water as well. The non-biodegradability of metal ions results in its accumulation in living organisms and causes various diseases. A low cost, specific, simple and quick tool is needed for monitoring heavy metals. The microbial biosensor specifically the Bioluminescence based ones provide an opportunity to solve this problem. The presence of the toxic heavy metal affects the expression of the lux gene and reduces the light density. As it can respond to any substance that is toxic to the microbe, this microbial biosensor is nonspecific. Specific biosensors, which are based on inducible promoters fused to reporter genes, are more sophisticated and sensitive. Only the specific biosensor can be used for in situ measurement of contaminants.
2. Heavy metal ions can act as an acute enzyme inhibitor and then cause some changes that can be used as the signal for detecting heavy metal ions. Example - mercury can inhibit the activity of alkaline phosphate enzymes present in the cell wall of Chlorella sp., Singh et al. developed a biosensor for determination of mercury by immobilizing Chlorella sp. on a glassy carbon surface. The use of genetically engineered bacteria, which can produce measurable signals when contacted with bio-components, is the best approach for detecting heavy metal. Ravikumarzra et al. constructed a biosensor for detecting zinc and copper based on engineered bacteria, where P and cusC promoters were fused to a dual-labeling reporter protein as an interactive biocomponent for zinc and copper to generate a signal from the constructed biosensor. A promoterless enhanced green fluorescent protein (egfp) gene was fused with the czcR3 promoter, which could respond quantitatively to zinc, for specific detection of zinc.
3. Using dead biomass to uptake heavy metals passively is a more efficient, economical and easier way for detecting them. Compared to living cells, dead biomass requires no nutrients, is easy to handle and store, and has high tolerance to toxic harsh reaction environments. Pseudomonas aeruginosa were used in a heat dried form to construct a microbial biosensor for the detection of heavy metal Pb (II).
4. Organic toxicity is another main pollutant in the environment which is harmful to human beings. A rapid, low-cost, and specific method for monitoring of various organic toxicities is needed. Microbial biosensors provide an alternative to solve this problem.

Soil Pollutants - defined as the presence of toxic chemicals (pollutants or contaminants) in soil, in high enough concentrations to pose a risk to human health and/or the ecosystem. Various biological techniques may use specific organisms to gauge not only contaminant level but also by-products of contaminant biodegradation in soil. These techniques and others are increasingly becoming more efficient, and laboratory instrumentation is becoming more precise, resulting in more meaningful monitoring outcomes. Arsenic biosensor is one such example for such.

ADVANCEMENTS

Like it is said, there is always room for improvement be it anything, similarly, several advancements have been and can be made even in this field for monitoring or detecting pollutants in and around the environment. Some of them are as follows:

• Biotechniques to treat emerging pollutants from water, air, and leachate, including endocrine disruptors is one of the latest inventions.
• Development of new biocatalysts and innovative bioreactors for pollution control and biotransformations: membrane bioreactors, microbial fuel cells, and alternative bioreactor configurations, among others are sought to be of great use for the desired.
• Introduction of various real-time monitoring advanced systems can also reduce the excessive consumption of several harsh chemicals and reagents with an added advantage of on-site determination of contaminant composition prior to discharge into the environment.
• More collaborative projects between the research community and government is of utmost importance for using the full potential of data in marine pollution management and others.
• Different applications of remote sensing such as detection of floating marine plastic litter and the use of active remote sensing for detecting algal blooms are still in the research.

CONCLUSION

Pollution is defined as the introduction of contaminants into the natural environment that causes adverse change in it. They can take the forms of chemical substances or energies, such as noise, heat or light. As demand for the use of sustainable and eco-friendly environmental processes is rapidly growing, Biotechnology provides a pool of opportunities for effectively addressing issues pertaining to the monitoring, assessment, and treatment of contaminated water, air, and solid waste streams comprising of these pollutants, which are great risks for the health of human beings. The adverse effects of these pollutants to human and other organism and the planet demands an appropriate method for its detection or monitoring that will further help to find treatments, preventive measures and degradation. With the help of Biomonitoring where use of Biotechnological tools and techniques is done, the development of various biological remote sensor like products that help in monitoring the presence of these pollutants by either measuring its toxicity level, ill effects on the native habitat animals, etc is done. These include biosensors, microextrantion tools, bioindicators, and biomarkers and so on. All of these help monitor air, water, soil pollutions but are not limited to just these. As more and more progress is made in the field of Biotechnology, Environmental Biotechnology is focused on precisely, specifically for pollution related contents like this one where monitoring of pollution is done. With these advancements, more high-tech and specialized pollutants monitoring techniques are expected to be formulated and made that would benefit the human world and the society in the days to come. Real-time pollutants monitoring facility, pollutant or organism, place or habitat specific pollutants monitoring systems, class specific heavy metal pollutants monitoring process are subjected to come into highlight in the near future to help mankind create a better and sustainable environment both for the existing and upcoming generations.