Microbial biosensors for wastewater monitoring: mini-review

Research on the use of microbial biosensors for monitoring wastewater contaminants is a topic that covers few publications compared to their applicability in other fields, such as biomedical research. For this reason, a systematic analysis of the topic was carried out, for which research-type articles were reviewed during the period 2012 to September 2022. For this, different search platforms were used, including PubMed, ScienceDirect, Springer Link, and Scopus, and through the use of search equations a relevant bibliography was located. After that, the research articles were selected based on exclusion criteria. As a result, it was found that, of the 126 articles, only 16 articles were strictly related to the topic, since there was a duplication of articles among the different databases. It was possible to demonstrate the usefulness of microorganisms as components of biosensors to monitor BOD, heavy metals, and inorganic contaminants in wastewater that also had a high sensitivity. Additionally, recombinant DNA techniques were shown to improve the performance of this type of biosensor and can finally be coupled to other emerging technologies, such as microbial fuel cells (MFCs). In conclusion, it was established that microbial biosensors have high acceptability and monitoring characteristics that make them a useful tool to detect low concentrations of pollutants in wastewater that can also provide results in real-time, thus generating forms of ecological safety and social responsibility in companies where wastewater is generated.Campus Trujill

Arsenic Biosorption by the Macroalgae Chondracanthus chamissoi and Cladophora sp.

The biosorption of arsenic (As) with macroalgae has aroused much interest as a clean and low-cost technology. To evaluate arsenic biosorption by Chondracanthus chamissoi and Cladophora sp., approximately 5 kg of algae was collected from Huanchaco’s beach and Sausacocha lake (Huamachuco), La Libertad. As biosorption was carried out in four column systems, with 2 g of algae pellets each, circulating As solutions of 0.25 and 1.25 ppm, respectively, at 300 mL/min cm2. As concentration was determined at 3 and 6 h of treatment by flame atomic absorption spectrophotometry. Data were analyzed using Student’s t-test with 95% confidence. At 6 h, Chondracanthus chamissoi presented an As biosorption of 95.76% in a 0.25 ppm mg/L solution and 85.33% in a 1.25 mg/L solution. Cladophora sp., at 6 h, presented an As biosorption of 95.76% in a 0.25 mg/L solution and 42.03% in a 1.25 mg/L solution. It was concluded that Chondracanthus chamissoi achieves higher percentages of biosorption than Cladophora sp. in solutions of 1.25 mg/L As (p 0.05)

Preliminary Study of Bioelectricity Generation Using Lettuce Waste as Substrate by Microbial Fuel Cells

"Agricultural waste negatively impacts the environment and generates economic difficulties for agro-industrial companies and farmers. As a result, it is necessary for an eco-friendly and sustainable alternative to managing this type of waste. Therefore, the research aimed to investigate lettuce waste as an alternative substrate to generate bioelectricity in single-chamber microbial fuel cells (scMFCs). It was possible to report voltage and electric current peaks of 0.959 ± 0.026 V and 5.697 ± 0.065 mA on the fourteenth day, values that were attained with an optimum pH of 7.867 ± 0.147 and with an electrical conductivity of 118.964 ± 8.888 mS/cm. Moreover, as time passed the values began to decline slowly. The calculated value of maximum power density was 378.145 ± 5.417 mW/cm2 whose current density was 5.965 A/cm2 , while the internal resistance reported using Ohm’s Law was 87.594 ± 6.226 Ω. Finally, it was possible to identify the Stenotrophomonas maltophilia bacterium (99.59%) on a molecular scale, as one of the microorganisms present in the anodic biofilm. The three microbial fuel cells were connected in series and demonstrated that they were capable of lighting an LED bulb, with a voltage of 2.18 V.

In Vitro Effect of Molasses Concentration, pH, and Time on Chromium Removal by Trichoderma spp. from the Effluents of a Peruvian Tannery

The effluents generated by the tannery industry have a high content of chromium and other toxic elements, representing a potential threat to ecosystems. An eco-friendly alternative to treat these effluents is the use of microorganisms, such as fungi, with the capacity to biosorb heavy metals. The present work aims to determine the effect of the molasses concentration, pH variation, and time on the removal of total chromium using the filamentous fungus Trichoderma spp. An experimental design was adopted using pH (4 and 6), concentrations of molasses (0.5 and 1%), and time (8 and 12 days) as independent variables. The Trichoderma inoculum was constant in all the treatments. The different treatments were evaluated after 0, 8, and 12 days by taking 50 mL of sample from each bioreactor. The chromium concentration was subsequently determined in each sample. The results show that treatment 3 (1% molasses and pH 4) showed higher chromium removal after both 8 and 12 days. The concentrations of total chromium decreased from 665 mg/mL to values of 568 mg/mL by day 8 and 486 mg/mL by day 12. These values are, however, still above the maximum threshold imposed by Peruvian law regarding the discharge of non-domestic effluents into the sewage system. The results show that Trichoderma spp. can increasingly remove chromium from the effluent with longer incubation periods. However, future studies are necessary to determine the mechanisms of chromium biosorption by the fungus and the influence of other physicochemical parameters

In Vitro Effect of Molasses Concentration, pH, and Time on Chromium Removal by Trichoderma spp. from the Effluents of a Peruvian Tannery

The effluents generated by the tannery industry have a high content of chromium and other toxic elements, representing a potential threat to ecosystems. An eco-friendly alternative to treat these effluents is the use of microorganisms, such as fungi, with the capacity to biosorb heavy metals. The present work aims to determine the effect of the molasses concentration, pH variation, and time on the removal of total chromium using the filamentous fungus Trichoderma spp. An experimental design was adopted using pH (4 and 6), concentrations of molasses (0.5 and 1%), and time (8 and 12 days) as independent variables. The Trichoderma inoculum was constant in all the treatments. The different treatments were evaluated after 0, 8, and 12 days by taking 50 mL of sample from each bioreactor. The chromium concentration was subsequently determined in each sample. The results show that treatment 3 (1% molasses and pH 4) showed higher chromium removal after both 8 and 12 days. The concentrations of total chromium decreased from 665 mg/mL to values of 568 mg/mL by day 8 and 486 mg/mL by day 12. These values are, however, still above the maximum threshold imposed by Peruvian law regarding the discharge of non-domestic effluents into the sewage system. The results show that Trichoderma spp. can increasingly remove chromium from the effluent with longer incubation periods. However, future studies are necessary to determine the mechanisms of chromium biosorption by the fungus and the influence of other physicochemical parameters

Impact of Dragon Fruit Waste in Microbial Fuel Cells to Generate Friendly Electric Energy

Pollution generated by the misuse of large amounts of fruit and vegetable waste has become a major environmental and social problem for developing countries due to the absence of specialized collection centers for this type of waste. This research aims to generate electricity in an eco-friendly way using red dragon fruit (pitahaya) waste as the fuel in single-chamber microbial fuel cells on a laboratory scale using zinc and copper electrodes. It was possible to generate voltage and current peaks of 0.46 ± 0.03 V and 2.86 ± 0.07 mA, respectively, with an optimum operating pH of 4.22 ± 0.09 and an electrical conductivity of 175.86 ± 4.72 mS/cm at 8 °Brix until the tenth day of monitoring. An internal resistance of 75.58 ± 5.89 Ω was also calculated with a maximum power density of 304.33 ± 16.51 mW/cm2 at a current density of 5.06 A/cm2, while the FTIR spectra showed a decrease in the initial compounds and endings, especially at the 3331 cm−1 peaks of the O–H bonds. Finally, the yeast-like fungus Geotrichum candidum was molecularly identified (99.59%). This research will provide great opportunities for the generation of renewable energy using biomass as fuel through electronic devices with great potential to generate electricity

An In Vitro Study of the Effects of Temperature and pH on Lead Bioremoval Using Serratia marcescens

Heavy metal contamination of water is a widespread problem in Peru and represents a potential threat to the ecosystem. Bacteria are an ecological alternative to treating these effluents. This research aims to determine the influence of temperature and pH on the lead (Pb) bioremoval in surface water using Serratia marcescens under laboratory conditions. The sample was collected from a stream located in Santiago de Chuco City (Peru). Treatments (T) were carried out by combining pH (5 and 7) and temperature (25, 30, and 35 °C). The bacterial inoculum (S. marcescens) was 3 × 108 CFU/mL, which was constant in all treatments. The lead bioremoval evaluation was performed in an airlift bioreactor and the incubation time was 24 h. The total lead concentration was determined using atomic absorption spectrophotometry. The results show that treatment 6 (temperature: 35 °C, pH: 5, and inoculum: 3 × 108 UFC/mL) showed a better result than the other treatments, with a removal value of 63.94%. Furthermore, the total lead concentration decreased from an initial concentration of 0.268 mg Pb/L to a final value of 0.0964 mg Pb/L. These results are still above the allowed water value (15 µg/L) according to Peruvian standards. On the other hand, temperature and pH influenced lead removal from surface water when S. marcescens was used after a short incubation period (24 h). Although an attempt was made to improve lead bioremoval by varying two parameters, temperature and pH, future research is still needed to investigate the effect of different inoculum concentrations, the use of microbial consortia, and a broader range of physicochemical parameters

Use of Kiwi Waste as Fuel in MFC and Its Potential for Use as Renewable Energy

This research aimed to use kiwi waste as fuel to generate bioelectricity through microbial fuel cells. It was possible to generate an electrical current and voltage peaks of 3.807 ± 0.102 mA and 0.993 ± 0.061 V on day 11, showing an electrical conductivity of 189.82 ± 3.029 mS/cm and an optimum operating pH of 5.966 ± 0.121. The internal resistance of the cells was calculated using Ohm’s Law, resulting in a value of 14.957 ± 0.394 Ω, while the maximum power density was 212.68 ± 26.84 mW/m2 at a current density of 4.506 A/cm2. Through the analysis of the FTIR spectra carried out on the substrate, a decrease in the characteristic organic peaks was observed due to their decomposition during the electricity-generation process. In addition, it was possible to molecularly identify the bacteria Comamonas testosteroni, Sphingobacterium sp., and Stenotropho-monas maltophila adhered to the anodized biofilm. Finally, the capacity of this residue to generate bioelectricity was demonstrated by lighting an LED bulb with a voltage of 2.85 V

Use of tangerine waste as fuel for the generation of electric current

Fruit waste has increased exponentially worldwide, within which tangerine is one of those that generates a greater amount of organic waste, which is currently not fully used. On the other hand, microbial fuel cells (MFCs) are presented as an opportunity to take advantage of organic waste to generate electricity, which is why the main objective of this research is to generate bioelectricity using tangerine waste as a substrate in microbial fuel cells using zinc and copper electrodes. It was possible to generate current and voltage peaks of 1.43973 ± 0.05568 mA and 1.191 ± 0.035 V on days eighteen and seventeen, respectively, operating with an optimum pH of 4.78 ± 0.46 and with electrical conductivity of the substrate of 140.07 ± 3.51 mS/cm, while the Brix degrees gradually decreased until the last day. The internal resistance determined was 65.378 ± 1.967 Ω, while the maximum power density was 475.32 ± 24.56 mW/cm2 at a current density of 5.539 A/cm2 with a peak voltage of 1024.12 ± 25.16 mV. The bacterium (Serratia fonticola) and yeasts (Rhodotorula mucilaginosa) were identified in the substrate with an identity of 99.57 and 99.50%, respectively. Finally, the cells were connected in series, managing to generate 3.15 V, which allowed the turning on of a red LED light.Campus Trujill

Green Energy Generated in Single-Chamber Microbial Fuel Cells Using Tomato Waste

"This research used tomato waste as a substrate (fuel) in Single Chamber-Microbial Fuel Cells (scMFC) on a small scale. The electrochemical properties were monitored, the functional groups of the substrate were analyzed by Fourier Transform Infrared Spectrophotometry (FTIR) and a microbiological analysis was performed on the electrodes in order to identify the microorganisms responsible for the electrochemical process. The results show voltage peaks and an electrical current of 3.647 ± 0.157 mA and 0.957 ± 0.246 V. A pH of 5.32 ± 0.26 was measured in the substrate with an electrical current conductivity of 148,701 ± 5849 mS/cm and an internal resistance (Rint) of 77. 517 ± 8.541 Ω. The maximum power density (PD) displayed was 264.72 ± 3.54 mW/cm2 at a current density (CD) of 4.388 A/cm2 . On the other hand, the FTIR spectrum showed a more intense decrease in its peaks, with the compound belonging to the phenolic groups being the most affected at 3361 cm−1 . The micrographs show the formation of a porous biofilm where molecular identification allowed the identification of two bacteria (Proteus vulgaris and Proteus vulgaris) and a yeast (Yarrowia lipolytica) with 100% identity. The data found show the potential of this waste as a source of fuel for the generation of an electric current in a sustainable and environmentally friendly way, generating in the near future a mechanism for the reuse of waste in a beneficial way for farmers, communities and agro-industrial companies.