NoMoldAtlanta

Call Today For a Free Consultation 678-671-2251

Evaluation of Microbial Growth and Survival on Construction Materials Treated with "Microbial Shield"

INTRODUCTION

The NoMoldAtlanta, Scottsdale, Arizona, is marketing "Microbial Shield", to control microbial growth in residential and commercial buildings. A study was performed to evaluate the product against some of the most common microorganisms detected in indoor air samples in water-damaged building materials. The test microorganisms included three types of bacteria (Escherichia, Bacillus, and Salmonella) and two types of fungi (Penicillium and Stachybotrys). The test and control samples for this study were provided by NoMoldAtlanta. All the test material was treated with "Microbial Shield" by NoMoldAtlanta. The microbial challenge studies were conducted at the National Science Foundation Water Quality Center at Arizona State University. The study was planned to evaluate the potential for microbial growth on construction materials inoculated with selected microorganisms before and after treatment with “Microbial Shield” agent. Mycelial fragments, fungal spores, and bacterial cells are commonly detected in indoor air samples and on water-damaged building materials. These facts were considered in the experimental plan. For the mold challenge study, separate set of experiments were performed to test the "Microbial Shield" agent against fungal mycelium and fungal spores. Experiments with bacterial agents were performed using actively growing bacterial cells. Research was conducted in controlled environmental chambers, and temperature and relative humidity were monitored regularly. Experiments were designed to determine the ability of the Microbial Shield to both deflect microbial growth. The objective of this study was to verify the proof of concept for microbial inactivation capabilities of the Microbial Shield agent on drywall and pinewood.

MATERIAL AND METHODS

Test Microorganisms

The pure cultures of E. coli (ATCC 25922), Bacillus subtilis (ATCC 27689), Salmonella typhimurium (ATCC 700730), Penicillium chrysogenum (ATCC 10134) and Stachybotrys chartarum (ATCC 18541) were obtained from American Type Culture Collection (ATCC Manassas, VA). The standard procedures described in the Standard Methods for the Examination of Water and Wastewater, 19th Edition were followed for bacterial culture maintenance, propagation, and samples assays. The fungal cultures were maintained on culture media recommended by ATCC using standards methods (Table1).

The material tested in this study was provided by NoMoldAtlanta. The test material consisted 3x3" coupons of pinewood and drywall thoroughly treated with "Microbial Shield" agent. In this study, non-treated coupons of drywall and pinewood were included as control samples. The surface area of each coupon was divided into six inoculation zones (Figure1). Each inoculating zone was seeded with specified number of microorganisms.

Inoculation Strategy

For the mold challenge study, two strategies were used to inoculate the test and control samples. The first strategy included the use of actively growing fungal mycelium on agar media. One-centimeter diameter fungal-mycelial-mats were cut from actively growing pure cultures of Penicillium and Stachybotrys. The fungal mats were placed on samples in inverted position. In these positions, fungal mycelia were cushioned between samples surface and nutrient medium, which provided the best possible scenario for initiation to initiate fungi on samples. This scenario never happens in real world; however, the technique was employed to provide the worst test conditions.

The second strategy included the use of fungal spores to inoculate test material. Pure cultures of Penicillium and Stachybotrys were grown in petri dishes and maintained until full sporulation was achieved. Fungal spores were transferred onto coupons by direct contact methods. Approximately, 10 million spores were deposited on each sample points in all samples. This inoculation method represents the natural scenario where airborne spores land on building materials and initiate fungal growth under favorable conditions.

For bacterial challenge study, drywall and pinewood coupons treated with Microbial Shield agent were inoculated with high numbers (~10⁸) of each of the bacterial species. Control samples for drywall and pinewood materials were also inoculated with same number of test bacterial species. Samples were incubated for 15 days. Test and control samples were assayed from the respective bacterial species at specified time interval.

Scientific Results