Simultaneous detection of three sex steroid hormone classes using a novel yeast-based biosensor

Steroid hormone-inducible biosensor based on EGFP-tagged and environmental application

Steroid hormones as a class of emerging organic pollutant and high concern, due to their potential risks for human and environmental. Accurate analytical methods of steroid hormones are necessary in quantifying and monitoring. Biosensor is a promising technique. In this study, though part of 3α-HSD DNA to construct a regulatory plasmid and with the EGFP reporter gene to generate a reporter plasmid. Separately transformed into Escherichia coli strain BL21 and extracted the cell lysates as novel biosensor reagents. Analyzed the total amounts of steroid hormones in water, sediment, and soil samples using biosensor reagents, and compared these results with those obtained by HPLC. In summary, detection method using an EGFP reporter that can detect trace amounts of steroid hormones to reached fg/L. The optimal reaction time range and temperature were 30 min and 30 °C, respectively, while the most suitable organic solvent for the steroid hormone was 100% ethanol, up to 96-well plate format. This method is very suitable for high-throughput detection of environmental steroid hormone pollutants.

Assessment of micropollutants toxicity by using a modified Saccharomyces cerevisiae model

Environment can be affected by a variety of micropollutants. In this paper, we develop a system to assess the toxicity on an environmental sample, based on the expression of a nanoluciferase under the control of the STB5 promotor in a yeast. The STB5 gene encodes for a transcription factor involved in a pleiotropic drug resistance and in the oxidative stress response. The response of the modified yeast was assessed using 42 micropollutants belonging to different families (antibiotics, pain killers, hormones, plasticizers, pesticides, etc.). Among them, 26 induced an increase of the bioluminescence for concentration ranges from pg.L^-1 to ng.L^-1. Surprisingly, for concentrations higher than 100 ng.L^-1, no response can be observed, suggesting that other mechanisms are involved when the stress increases. Analyzing the different responses obtained, we highlighted six nonmonotonic types of responses. The type of response seems to be independent of the properties of the compounds (polarity, toxicology, molecular weight) and of their family. In conclusion, we highlighted that a cellular response exists for very low exposition to environmental concentration of micropollutants and that it was necessary to explore the cellular mechanisms involved at very low concentration to provide a better risk assessment.

Recent trends in biocatalysis

Biocatalysis has undergone revolutionary progress in the past century. Benefited by the integration of multidisciplinary technologies, natural enzymatic reactions are constantly being explored. Protein engineering gives birth to robust biocatalysts that are widely used in industrial production. These research achievements have gradually constructed a network containing natural enzymatic synthesis pathways and artificially designed enzymatic cascades. Nowadays, the development of artificial intelligence, automation, and ultra-high-throughput technology provides infinite possibilities for the discovery of novel enzymes, enzymatic mechanisms and enzymatic cascades, and gradually complements the lack of remaining key steps in the pathway design of enzymatic total synthesis. Therefore, the research of biocatalysis is gradually moving towards the era of novel technology integration, intelligent manufacturing and enzymatic total synthesis.

A fluorescence-based yeast sensor for monitoring acetic acid

Accumulation of acetic acid indicates an imbalance of the process due to a disturbed composition of the microorganisms. Hence, monitoring the acetic acid concentration is an important parameter to control the biogas process. Here, we describe the generation and validation of a fluorescence-based whole cell sensor for the detection of acetic acid based on the yeast Saccharomyces cerevisiae. Acetic acid induces the transcription of a subset of genes. The 5´-regulatory sequences (5´ URS) of these genes were cloned into a multicopy plasmid to drive the expression of a red fluorescent reporter gene. The 5´ URS of YGP1, encoding a cell wall-related glycoprotein, led to a 20-fold increase of fluorescence upon addition of 30 mM acetic acid to the media. We show that the system allows estimating the approximate concentration of acetic acid in condensation samples from a biogas plant. To avoid plasmid loss and increase the long-term stability of the sensor, we integrated the reporter construct into the yeast genome and tested the suitability of spores for long-term storage of sensor cells. Lowering the reporter gene's copy number resulted in a significant drop of the fluorescence, which can be compensated by applying a yeast pheromone-based signal amplification system.

High-performance thin-layer chromatography in combination with a yeast-based multi-effect bioassay to determine endocrine effects in environmental samples

Effect-directed analysis (EDA) that combines effect-based methods (EBMs) with high-performance thin-layer chromatography (HPTLC) is a useful technique for spatial, temporal, and process-related effect evaluation and may provide a link between effect testing and responsible substance identification. In this study, a yeast multi endocrine-effect screen (YMEES) for the detection of endocrine effects is combined with HPTLC. Simultaneous detection of estrogenic, androgenic, and gestagenic effects on the HPTLC plate is achieved by mixing different genetically modified Arxula adeninivorans yeast strains, which contain either the human estrogen, androgen, or progesterone receptor. Depending on the yeast strain, different fluorescent proteins are formed when an appropriate substance binds to the specific hormone receptor. This allows to measure hormonal effects at different wavelengths. Two yeast cell application approaches, immersion and spraying, are compared. The sensitivity and reproducibility of the method are shown by dose-response investigations for reference compounds. The spraying approach indicated similar sensitivities and higher precisions for the tested hormones compared to immersion. The EC₁₀s for estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), 5α-dihydrotestosterone (DHT), and progesterone (P4) were 95, 1.4, 10, 7.4, and 15 pg/spot, respectively. Recovery rates of E1, E2, EE2, DHT, and P4 between 88 and 120% show the usability of the general method in combination with sample enrichment by solid phase extraction (SPE). The simultaneous detection of estrogenic, androgenic, and gestagenic effects in wastewater and surface water samples demonstrates the successful application of the YMEES in such matrices. This promising method allows us to identify more than one endocrine effect on the same HPTLC plate, which saves time and material. The method could be used for comparison, evaluation, and monitoring of different river sites and wastewater treatment steps and should be tested in further studies.

Estrogenic activity of biological samples as a biomarker

Biological assays can evaluate the cumulative effect of a mixture, considering synergistic/antagonistic interactions and effects of unknown/unconsidered compounds. Therefore, their application could increase in the next years also to analyse biological samples. The aim of this review is to discuss the methodological approach and the application of estrogenic activity assays in human biological samples. 75 research articles were analysed and divided according to whether they used these assays: i) to quantify the level of estrogens and/or as a biomarker of estrogenic status ii) as a biomarker of exposure to endocrine disrupting chemicals (EDCs). For the first purpose, some authors extracted biological samples while others tested them directly without any treatment. The study of these methodologies outlined that the methodology applied influenced the specificity of analysis. The estrogenic activity biomarker was used to analyse physiological variations of estrogens, pediatric diseases, hormone-dependent diseases and estrogen suppression/enhancement after pharmaceutical treatments. For the second purpose, some authors extracted samples while others tested them directly, some authors divided endogenous estrogens from xenoestrogens while others tested samples without separation. The analysis of these methodologies outlined some limitations related to the efficiency of extraction and the incorrect separation of some compounds. The studies which applied this EDC biomarker showed that it was correlated with some EDCs, it varied according to the exposure of the population and it allowed the identification of some relationships between EDC exposure and breast cancer, type 1 diabetes and adverse health effects on children. In conclusion, the estrogenic activity of biological samples can be a useful tool: to quantify low levels of 17β-estradiol, to assess the combined effect of endogenous estrogens and xenoestrogens, to estimate the estrogenic status providing considerable insight into physiological or pathological conditions, to evaluate EDC presence implementing the existing knowledge about EDC exposure and adverse health effects.

Combination of yeast-based in vitro screens with high-performance thin-layer chromatography as a novel tool for the detection of hormonal and dioxin-like compounds

The combination of classic in vitro bioassays with high-performance thin-layer chromatography (HPTLC) is a promising technique to directly link chemical analysis of contaminants to their potential adverse biological effects. With respect to endocrine disruption, much work is focused on estrogenicity. While a direct combination of HPTLC and the yeast estrogen screen is already developed, it is well accepted that further endocrine effects are relevant for monitoring environmental wellbeing. Here we show that non-estrogenic specific biological endpoints, (partly) related to the endocrine system, can also be addressed by combining respective yeast reporter gene assays with HPTLC to support effect-directed analysis (EDA). These are: androgenicity (YAS), thyroidogenicity (YTS), dioxin-like effects (YDS), effects on the vitamin D (YVS) and the retinoic acid receptor (YRaS). A proof of principle is demonstrated within this study by the characterization of dose-dependent responses to different model compounds for the respective receptors with and without chromatographic development of the HPTLC-plate. Limits of quantification (LOQ) for several model compounds were determined, e.g. 37 pg for testosterone (p-YAS), 0.476 ng for β-naphthoflavone (p-YDS) and 1.02 ng for calcipotriol hydrate (p-YVS) with chromatographic development. The LOQ for p-YTS and p-YRaS were 10.16 pg for 3,3',5-triiodothyroacetic acid (p-YTS) and 0.41 pg for tamibarotene (p-YRaS), without chromatographic separation. Furthermore, we challenged the developed methodology using environmental samples, demonstrating an elimination efficiency of androgenic activity from municipal wastewater by a wastewater treatment plant between 99.4 and 100%. We anticipate our methodology to substantially broaden the spectrum of specific endpoints combined with HPTLC for an efficient and robust screening of environmental samples to guide a subsequent in-depth EDA.

Separation and identification of hormone-active compounds using a combination of chromatographic separation and yeast-based reporter assay

Arxula adeninivorans-based yeast cell assays for the detection of steroid hormones demonstrated their efficiency for the determination of total hormone activity in a variety of samples using a microtiter plate format. In this study, a preliminary chromatographic separation using thin-layer chromatography plates is introduced in order to allow a rapid identification of the compounds responsible for this hormonal activity. The yeast whole cell assay can then be performed on the plate, producing a detectable signal where a steroid hormone is present. Simultaneous detection of estrogens, progestogens and androgens on the same plate in the picogram range was achieved, while keeping the assay as simple and affordable as possible. The assay requires a single incubation of the thin-layer chromatography plate and the detection of reporter protein production can be performed by fluorescence scanning of the plate at different wavelengths. The chromatographic separation allows the separation of several estrogens, androgens and progestogens, thus making its application for 'real world' samples very useful. In this work, different water-based samples from environmental origins were used to demonstrate the capacity of this new bioassay. Trials showed that most samples, with the exception of complex samples such as wastewater influent, can be assayed.