Potential application of LASER/microbe bioassay technology for determining water-soluble vitamins in foods.

A microbiological technique was developed for quantitating niacin by determining microbial growth rates in response to the amount of vitamin available. Unlike the current official AOAC method, the new procedure for niacin measured the growth rates during the early exponential growth phase rather than during the stationary phase. Lactobacillus plantarum was used to determine niacin to a lower limit of 100 pg/mL. The assay time was approximately 6 h, compared with 16-24 h for the current AOAC method. The extent of microbial growth was determined by differential light scattering of a LASER beam. Multiple photodetectors were integrated with a computer system to collect and analyze the data. The use of differential light scattering to determine 8 water-soluble vitamins under stationary phase conditions demonstrated the potential application of the new technology for microorganisms and foods.

Quantitative bioassay using laser-monitored bacteria to assess toxicology and metabolism of bioactive Group IV compounds.

A new approach has been developed for assessing the toxicity and the metabolism of Group IV compounds and for other toxic substances that may interact with them at the molecular level. The approach is based upon the selective responses of sensitive biodetectors whose molecular interactions with a wide variety of toxic substances have been previously described and reported. Detection and quantitation of carbon, silicon, and tin-containing compounds has been accomplished using a laser-monitored bacterial bioassay. This system uses isogenic Bacillus subtilis strains that are genetically engineered to respond differentially to specific toxicants. The response of these biodetectors is monitored by differential light scattering of a laser that is integrated with a computerized system which collects and analyzes this data. The assay can routinely generate fully analyzed data for fixed time intervals, i.e. 60 or 90 min, or kinetic data so that the mechanisms of interactions can be elucidated.