<p><strong>Development of a portable, distance-based paper analytical sensor <br />for carbonate detection.</strong></p> <p> </p> <p><strong>Zakia Tebetyo<sup>1</sup>, Samantha Richardson<sup>1</sup>,</strong> <strong>Leigh Madden<sup>2</sup>,</strong> <strong>Mark Lorch<sup>1</sup>, Nicole Pamme<sup>1,3</sup></strong></p> <p><em><sup>1</sup></em><em>School<sup> </sup>of Natural Sciences, University of Hull. </em></p> <p><em><sup>2 </sup></em><em>Centre for Biomedicine, Hull York Medical School, University of Hull, UK</em></p> <p><em><sup>3</sup></em><em>Department of Materials and Environmental Chemistry, Stockholm University, Sweden</em></p> <p>In this study we transferred a laboratory-based titration reaction for carbonate determination onto a portable paper-based analytical device (PAD). The carbonate quantity can be read out by measuring the distance of a colour change along a paper-based reaction channel. Device dimensions and detection reagent constituents were optimized to enable detection of carbonate ions in the range of 0 – 1000 mg L<sup>-1</sup>. The PAD featured a reaction channel in hydrophilic filter paper defined by a hydrophobic wax barrier. The detection reagent consisted of citric acid/citrate buffer (0.5 M, pH 2.5), bromocresol green (BCG) indicator (0.10% w/v) and PDADMAC (5.0 % v/v) dissolved in 20% ethanol. The base of the device was sealed with tape to prevent reagents leaking. Sixty microlitres of carbonate sample were added to the base of the channel and the liquid was allowed to wick up the channel. Colour development occurred as the carbonate ions reacted with the hydronium ions in the detection reagent resulting in a colour change of the BCG indicator from yellow to blue.</p> <p>To optimise the reaction channel, two dimensions were compared, 1 mm x 30 mm and 2 mm x 30 mm. The device with the wider channel gave a higher colour intensity between carbonate concentrations 0 – 200 mg L<sup>-1</sup>. In this range the sensor gave a linear response. The effect of filter paper pore size was investigated to study wicking time. Whatman 4 paper (pore size 23 µm) had a six times faster wicking rate of 7 min compared to Whatman 1 (11 µm) with 42 min. Reproducibility studies (100, 200, 400, 500, 600, 800 and 1000 ppm carbonate, n = 6) gave a maximum RSD of 2.4% showing consistency across the range of samples tested. Interference tests were conducted with 500 ppm  with additional environmentally occurring ions, i.e. 250 ppm , 250 ppm  or 50 ppm of  (F=1.924<Fcrit=3.411, no significant difference). There was no significant interference found from these ions.</p> <p>Future work will focus on packaging and sealing the devices for on-site use, benchmarking with real environmental samples and in-the-field use with by minimally trained personnel.</p>

The efficacy of two microbial isolates, Bacillus spp. (B285) and Saccharomyces spp. yeast strain (Y833), in reducing aflatoxin concentration in poultry feeds in comparison with the commonly used commercial chemical binder, bentonite, was investigated using the VICAM ® fluorometer. The influence of the poultry feed matrix, pH (4.5 and 6.5), and temperature (room temperature, 37 and 42ºC) on the aflatoxin reducing activity by the two microorganisms was also explored. All microorganisms and bentonite reduced aflatoxins by over 74% of the original concentration. Bentonite registered the highest reduction at 93.4%; followed by Y833 (83.6%), then the combination of Y833 and B285 (77.9%); and lastly B285 (74.9%). Temperature and pH did not have significant effect on the performance of the biological agents and bentonite. The aflatoxin reducing activity was lower in presence of feeds compared to that in phosphate buffered saline except for Y833. The yeast strain was more effective than the bacterial strain in reducing the aflatoxin levels; however, both are promising strategies for countering the aflatoxin challenges in animal feeds. In response to the advocacy for use of biological control agents, there is need for more investigations to establish the safety of the microorganisms and the mechanism of aflatoxin decontamination.

Background: Contamination of animal feeds with aflatoxigenic fungi is a challenge to livestock farmers worldwide. Aflatoxins are very toxic fungal metabolites that are associated with carcinogenic, mutagenic, teratogenic, and estrogenic effects. The toxins affect animal productivity and may lead to deaths, causing enormous economic losses. Aflatoxin decontamination is a challenge to the feed industry, despite the several approaches available. This study investigated the efficacy of two microbial isolates, Bacillus spp (B285) and Yeast strain (Y833), in reducing Aflatoxin concentration in poultry feeds in comparison with a commonly used commercial chemical binder, Bentonite. The influence of the poultry feed matrix, pH, and temperature on the aflatoxin reducing activity by the two microorganisms was also explored. Results: The in vitro studies showed that the two microorganisms and the chemical binder reduced aflatoxins by over 74% of the original concentration. The chemical binder registered the highest reduction at 93.4%; followed by Y833 (83.6%), then the combination of Y833 and B285 (77.9%); and lastly B285 (74.9%). There was no significant (p>0.05) influence of temperature on the toxin reducing capacity of all the agents tested. The pHs 4.5 and 6.5 did not have a significant effect on the performance of both chemical binder and biological agents, however, the former performed better at pH 6.5 with 95% aflatoxin reduction compared to the microorganisms. The aflatoxin reducing activity was lower in presence of feeds compared to that in Phosphate Buffered Saline except for Y833 where no difference was observed. Conclusions: Although the feed components affected the aflatoxin reducing capacity of the test materials, the chemical binder was more effective than the microbial agents. Yeast strain was more effective than the bacterial strain in reducing the aflatoxin levels, however, both are promising strategies for countering the aflatoxin challenges in animal feeds. In response to the advocacy for use of biological control agents, there is need for more investigations to establish the safety of the microorganisms, the mechanism of decontamination and safety of the products; the optimum concentrations that can reduce aflatoxins in feeds to permissible levels and the effect of the toxin contamination levels on microbial efficiency.