Effects of Different Broth Enrichment upon Phage Magnetoelastic Biosensor for Fast Detecting Low <i>Salmonella</i>Counts on Problematic Produce

According to the FDA Bacteriological Analytical Manual (BAM) for Salmonella identification in produce, two pre-enrichment steps with 48 hours of incubation are the golden procedures. Lactose broth is recommended for the first pre-enrichment step medium for leafy greens, and the universal pre-enrichment (UP) broth is for tomatoes. However, the suggested broths were evaluated to have the maximum performance using the culture-dependent methods, and may not be applied to other methods, such as biosensor detection platform. A wireless bacteriophage magnetoelastic (ME) biosensor has been recently developed for real-time or rapid detection of food-borne pathogens in various foods. This affinity-based biosensor utilizes a phage oligonucleotide as the probe to capture target bacteria. In this study, the efficiencies of different pre-enrichment media for early detection of low Salmonella on spinach leaves and tomatoes use ME biosensors to shorten detection time. Four broths of modified peptone water, Lennox broth (LB), lactose broth, and UP broth were selected in this study. Various pre-enrichment times for ME biosensor detection were investigated. After spiking 4 cfu/g Salmonella on the tomatoes surfaces, the phage biosensor was able to detect Salmonella within 5 hours of pre-enrichment comparing to 24 hours in the FDA procedures. For Salmonella spiked spinach leaves, the same medium showed Salmonella positive within 7 hours. This study demonstrated that LB broth is the best medium to shorten pre-enrichment time to pass Salmonella number detection thresholds for ME biosensor detection in spinach and tomatoes when comparing to FDA procedures.

Use of LPS Extracts to Validate Phage Oligopeptide That Binds All <i>Salmonella enterica</i>Serovars

Phage Display technology provides a mechanism for us to make bio-recognition elements on biosensors for detection of Salmonella enterica serovars. In the procedure, the filamentous M13 bacteriophage is used for acquiring peptides that have a high affinity for the target recognition. Our approach in this study was to develop peptide structures in the pIII region of this thread-shaped virus. A phage pIII library was used to perform biopanning for the phage clones to bind the target Salmonella serovars. The clones were bound, washed, eluted and amplified four times. Then, the phage peptides were sequenced tested for specificity using ELISA procedures. In this project to make a biosensor for all relevant Salmonella enterica serovars, we used common LPS salmonellae antigens as targets in the biopanning procedure. This enabled us to have a phage probe specific for all serovars of Salmonella enterica excluding the typhoid organisms. The final phage was then immobilized onto an electromagnetic platform to complete the biosensor, which gives us the real-time ability to measure resonance changes that indicate mass loading. The mass loading is an indication of binding to the target cells. Our current data with an ELISA procedure show the phage probe’s high affinity for salmonellae, very low cross-reactivity with Escherichia coli, Shigella, and no cross-reactivity to Staphylococcus aureus and Listeria monocytogenes. The biosensor with the phage showed that the capture ability for Salmonella serovars is thirty times higher than the control sensor. This biosensor is a candidate for detection of Salmonella in food and other settings.

用于农业和食品工业的传感器

现代农业管理在很大程度上有赖于许多不同种类的传感方法，以提供关于作物、土壤、气候和环境条件的准确信息。几乎每一类传感技术都可以在农业和食品工业中得到应用。本文将对传感器在农业和食品工业中的应用作一简略评述。

Scanning Mode Application of Neutron-Gamma Analysis for Soil Carbon Mapping

Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage. Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed. A Global Positioning System(GPS) device and softwares required to simultaneously acquire gamma signals and geographical positions during scanning operations were added to an existing measurement system. The reliability of soil carbon measurements in scanning mode was demonstrated to be in agreement with results acquired from static mode. The error analysis indicated that scanning measurements can be conducted with the same accuracy as static measurements in approximately one fourth the time. To obtain results suitable for mapping analogous to traditional chemical analyses(i.e.,± 0.5 in weight percent or ± 0.5 w%), scanning time over a given site should be ca. 15 min using the current measurement system configuration. Based on this measurement time, a reasonable towing speed of 3–5 km h^-1, the necessity for complete site coverage during scanning, the number of sites(within the surveyed field), and the required total measurement time can be estimated. Soil carbon measurements for 28 field sites(total area ca. 2.5 ha) were conducted in ca. 8 h. Based on acquired data,a soil carbon distribution map was constructed utilizing various softwares. The surveyed field area included an asphalt road that had carbon readings higher than the surrounding land. The clarity with which these carbon-rich zones were delineated on the constructed map represents evidence supporting the veracity of this method. Neutron-gamma analysis technology can greatly facilitate timely construction of soil carbon maps.