Characterization of luminous bacteria as a biosensing element for detection of acrylamide in food.

Abstract

World Health Organization (WHO) has called for further research into acrylamide, a known carcinogen and neurotoxin in animals, following emergency consultations to review data from studies that revealed the presence of acrylamide in starch-based foods fried and baked at high temperatures. The presence of acrylamide in food is recognized as a major concern in humans based on the ability to induce cancer and heritable mutations in laboratory animals. The objective of this study was to characterize the cellular-level damage of acrylamide by bioluminescence stress fingerprinting. Five genetically engineered strains containing selected stress-responsive E. coli promoters fused to the luxCDABE reporter were employed. One of the strains containing DNA damage responsive promoter, DPD2222, was also employed in conjunction with alkaline and neutral comet assay to assess respective single- and double-stranded DNA damages. Results showed that Luminous E. coli DPD2222 containing DNA damage responsive promoter, recA, yielded the highest response followed by luminous E. coli DPD2234 which contained protein damage responsive promoter, grpE. Moreover, acrylamide stress response of the cells up to 14 days old was the same as that of the overnight culture. Furthermore, it was revealed that the E. coli DPD2222 and DPD2234 were capable of detecting acrylamide between 1 and 10,000 μg/L upon contact, with the response signals proportional to acrylamide concentration. The most severe cellular damage of these two strains was achieved after 100 min of contact, as indicated by the highest signals. In addition, temperature-wise, 37 °C resulted in the most significant light emission of E. coli DPD2222. No single strand break was observed at acrylamide concentrations <1000 μg/L by using alkaline comet assay. However, neutral comet assay performed at acrylamide concentrations >10,000 μg/L (ambient temperature) showed a more severe DNA double strand breaks in the cells, so did 1000 μg/L acrylamide at 37 °C. Therefore, it is evident that exposure of bioluminescence sensing cells to acrylamide causes severe DNA damage at either high concentration at room temperature or reduced concentration at body temperature. Quantitative and fingerprint assessment of acrylamide damage could be achieved by optimizing bioluminescence cells constructed with different stress-responsive reporter plasmids.