Traditionally, direct‐reading instruments have been used to directly determine the concentrations of indoor air pollutants that may exceed the regulation limits. However, these instruments cannot directly assess the potential health hazards of these pollutants to humans. In this study, we developed and improved a bacterial reverse mutation assay (Ames test) by using a direct gas exposure module to directly determine the mutagenicity of indoor air quality using five tester bacterial strains (TA98, TA100, TA102, TA1535, and TA1537). Thereafter, the module was used to evaluate the effects of exposure time, different concentrations of HCHO or toluene, and mutagenic activities. We found that TA100 was the most sensitive strain and was reverted by relatively lower concentrations of 0.035 ppm HCHO. Furthermore, 50 ppm of toluene exposures caused a significant increase in the number of revertant colonies of TA100 without S9 activation at the 1.5–8‐h exposure time intervals. Our findings provide new evidence that gaseous HCHO exposure could display weak but direct, time‐dependent, and dose‐dependent mutagenic activities. The weak, direct‐acting, indirect‐acting, and time‐dependent mutagen of 50 ppm toluene was also confirmed. Moreover, our improved Ames module and the exposure conditions provided in this study can be further applied to evaluate the mutagenicity of indoor air quality.

Lactoferrin (LF) is a multifunctional protein found in mammals, and it shows broad-spectrum antimicrobial activity. To improve the functional properties of specific probiotics in order to provide both the beneficial characteristics of lactic acid bacteria and the biological activity of LF, cDNAs of bovine LF (BLF), human LF (HLF), or porcine LF (PLF) were cloned into a nisin-inducible plasmid. These were then transformed into the selected eight probiotics, which are LF-resistant hosts. Expression of recombinant LFs (rLFs) was analyzed via SDS-PAGE and Western blot analysis. Although the selected host strains may not contain the nisRK genes (NisK, the sensor kinase; NisR, the regulator protein), the components of autoregulation, a low level of LFs expression can be successfully induced by using nisin within bacterial cells in a time-dependent manner in three engineered clones, including Lactobacillus delbrueckii/HLF, L. delbrueckii/BLF, and L. gasseri/BLF. Lactobacillus delbrueckii and Lactobacillus gasseri originate from yogurt and human milk, respectively, and both strains are functional probiotic strains. Therefore, we further compared the antibacterial activities of disrupted recombinant probiotic clones, conventional strains (host control), and vector control ones by using agar diffusion and broth inhibition analysis, and the expression of rLFs in the above three clones considerately improved their antibacterial efficacies against four important food-borne pathogens, namely, Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, and Salmonellaenterica. In conclusion, this study provides a simple strategy for the production of functional LFs (BLF and HLF) in both functional and LF-resistant hosts for applications in the field.

We had previously developed an improved Ames module to directly determine the mutagenicity of gaseous formaldehyde (HCHO) and toluene without liquid extraction. This study further evaluated the suitability and sensitivity of this module on whole and real polluted air samples. For this, two common brands of stick incense (A and B) and cigarettes (A and B) were harvested, and various types of incense smoke (IS) and sidestream cigarette smoke (SCS) samples were generated by lighting 3, 6, 12, 24, 30, or 36 incense sticks, and by lighting 1, 2, or 3 cigarettes, respectively, in an acrylic box. CO2, CO, total volatile organic compound (TVOC), PM1.0, and HCHO concentrations in the air samples were determined, and all air samples did not partially fit the requirements of the air quality standards. The smoke samples were then directly exposed to TA100 for 10, 20, 30, or 60 min in our exposure module. Exposure to IS (brand A) for 30 to 60 min and exposure to IS (brand B) for 60 min led to statistically (p < 0.05) weak (below the twofold rule) but dose‐dependent mutagenic activities either with or without metabolic activation. Furthermore, a short‐term exposure (10–60 min) to SCS (brands A and B) displayed statistically significant (p < 0.05) direct‐acting, indirect‐acting, time‐ and dose‐dependent mutagenic activities. Furthermore, our data also support that the liver S9 enzyme could enhance the mutagenic activities in most IS and SCS samples. This study confirmed that the modified Ames module can be applied to directly detect the mutagenic activities of real polluted air samples.