Juan Francisco Villarreal-Chiu

Scenario of organophosphate pollution and toxicity in India: A review

The present study on organophosphate deals with the reports on pollution and toxicity cases throughout India. The use of pesticides was introduced in India during the 1960s which are now being used on a large scale and represents the common feature of Indian agriculture. Use of organophosphates as a pesticide came as an alternative to chlorinated hydrocarbons due to their easy degradability. Although these xenobiotics degrade under natural condition, their residues have been detected in soil, sediments, and water due to their non-regulated usage practice. The over-reliance on pesticides has not only threatened our environment but contaminations of organophosphate residues have been also detected in certain agricultural products like tea, sugars, vegetables, and fruits throughout India. This paper highlights many of the cases where different organophosphates have been detected exceeding their respective MRL values. Some organophosphates detected are so hazardous that even WHO has listed them in class 1a and class 1b hazardous group. Presence of their residues in blood, milk, honey, and tissues of human and animals revealed their excessive use and bioaccumulating capabilities. Their intentional or unintentional uptake is causing thousands of deaths and severity each year. Most of the toxicity cases presented here are due to their uptake during a suicidal attempt. This shows how easily these harmful substances are available in the market.

Metal-Induced Production of a Novel Bioadsorbent Exopolysaccharide in a Native Rhodotorula mucilaginosa from the Mexican Northeastern Region

There is a current need to develop low-cost strategies to degrade and eliminate industrially used colorants discharged into the environment. Colorants discharged into natural water streams pose various threats, including: toxicity, degradation of aesthetics and inhibiting sunlight penetration into aquatic ecosystems. Dyes and colorants usually have complex aromatic molecular structures, which make them very stable and difficult to degrade and eliminate by conventional water treatment systems. The results in this work demonstrated that heavy metal-resistant Rhodotorula mucilaginosa strain UANL-001L isolated from the northeast region of Mexico produce an exopolysaccharide (EPS), during growth, which has colorant adsorption potential. The EPS produced was purified by precipitation and dialysis and was then physically and chemically characterized by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and chemical elemental analysis. Here, the ability of the purified EPS produced to adsorb methylene blue (MB), which served as a model colorant, is studied. MB adsorption by the EPS is found to follow Langmuir Adsorption Isotherm kinetics at 25°C. Further, by calculating the Langmuir constant the adsorption capabilities of the EPS produced by the Rhodotorula mucilaginosa strain UANL-001L is compared to that of other adsorbents, both, microbially produced and from agroindustrial waste. The total adsorption capacity of the EPS, from the Rhodotorula mucilaginosa strain UANL-001L, was found to be two-fold greater than the best bioadsorbents reported in the literature. Finally, apart from determining which heavy metals stimulated EPS production in the strain, the optimal conditions of pH, heavy metal concentration, and rate of agitation of the growing culture for EPS production, was determined. The EPS reported here has the potential of aiding in the efficient removal of colorants both in water treatment plants and in situ in natural water streams.

Polishing of municipal secondary effluent using native microalgae consortia

This work evaluates the use of native microalgae consortia for a dual role: polishing treatment of municipal wastewater effluents and microalgae biomass feedstock potential for biodiesel or biofertilizer production. An initial screening was undertaken to test N and P removal from secondary effluents and biomass production by 12 consortia. A subsequent treatment was performed by selected consortia (01 and 12) under three operational conditions: stirring (S), S + 12 h of daily aeration (S + A) and S + A enriched with CO2 (S + AC). All treatments resulted in compliance with environmental regulations (e.g. Directive 91/271/EEC) and high removal efficiency of nutrients: 64-79% and 80-94% of total N and PO43--P respectively. During the experiments it was shown that pH alkalinization due to microalgae growth benefits the chemical removal of ammonia and phosphorus. Moreover, advantages of pH increase could be accomplished by intermittent CO2 addition which in this research (treatment S + AC) promoted higher yield and lipid concentration. The resulting dry biomass analysis showed a low lipid content (0.5-4.3%) not ideal for biodiesel production. Moreover, the high rate of ash (29.3-53.0%) suggests that biomass could be readily recycled as a biofertilizer due to mineral supply and organic constituents formed by C, N and P (e.g. carbohydrate, protein, and lipids).

Biological Limitations on Glyphosate Biodegradation

Glyphosate is currently considered the most important herbicide of the world due to its broad-spectrum activity, effectiveness, and loss of global patent protection. Its ubiquitous presence in the environment due to anthropogenic activities and recalcitrance has the potential to affect animal behavior and interfere with ecological processes. Despite its important role in the protection of crops, it is important to establish strategies to reduce potential human exposure or decrease its presence in the environment. To date, only one microbial enzyme known as C-P lyase is acknowledged to drive complete glyphosate mineralization. AMPA, the common metabolite product of glyphosate biodegradation, still possesses the unique C-P bond of phosphonates and retains it toxic profile and recalcitrance. Thus, it is important to consider glyphosate and AMPA biodegradation altogether. Nevertheless, the potential to develop a bioremediation process is mainly limited by the genetic regulatory system that governs the expression of the C-P lyase, as it strongly depends on low environmental levels of phosphate. Thus, the complete mineralization of this herbicide by the sole use of microorganisms would remain insufficient until (1) more research on additional genetic control mechanisms of C-P lyase expression are explored, (2) alternative enzymes are studied in detailed, or (3) more complex and elaborated processes are considered. This work explores the available information on glyphosate biodegradation over the course of 40 years of study, the different pathways involving the C-P lyase, the genetic and physiological regulatory system that governs these processes, and the factors limiting the development of glyphosate bioremediation technologies.

Reduction of Chromium (VI) from aqueous solution by biomass of Cladosporium cladosporioides

The capacity of Cladosporium cladosporioides biomass for removal of Cr(VI) in aqueous solutions was evaluated. A 2 × 2 factorial experiment design was used to study the effects of pH and biomass doses. Lower pH values and larger biomass doses increased the capacity of C. cladosporioides biomass for removal of Cr(VI), reaching a reduction capacity of 492.85 mg g-1, a significantly higher value compared to other biomass reported. Cr(VI) removal kinetic rates followed a pseudo-second order model, like other fungal biomass reported previously. The apparent adsorption process was described well by the Freundlich isothermal model. However, determination of total chromium indicated that adsorption of Cr(VI) was followed by a redox reaction that released proportional quantities of Cr(III) into the experimental supernatant, suggesting a parallel adsorption-reduction process. Comparison of Fourier transform infrared spectroscopy spectra of C. cladosporioides biomass before and after the reduction process demonstrated the involvement of positively charged amino groups in the Cr(VI) adsorption-reduction process.

Metallophilic fungi research: an alternative for its use in the bioremediation of hexavalent chromium

Contamination by hexavalent chromium has had a large impact on modern society and human health. This problem is a consequence of its great industrial applicability to several products and processes. Short-term exposure to hexavalent chromium can cause irritation, ulceration in skin and stomach and in addition to cancer, dermatitis, and damage to liver, renal circulation and nervous tissues, with even death being observed in response to long-term exposures. Many techniques have been used for the remediation of this pollutant, including physical and chemical approaches and, in more recent years, biological methods. Filamentous fungi isolated from contaminated sites exhibit a significant tolerance to heavy metal; hence, they are an important source of microbiota capable of eliminating hexavalent chromium from the environment. However, these microorganisms can do so in different ways, including biosorption, bioreduction, and bioaccumulation, among others. In this review, we explore several of the most documented mechanisms that have been described for fungi/hexavalent chromium interactions and their potential use in bioremediation.