Microbial biosensors are analytical devices composed of a biological recognition element (microorganism) integrated to a signal transduction element (i.e. bioluminescence), converting a biochemical signal into quantifiable response. Due to their molecular properties they can be diversely designed in order to fulfill the needs of different fields, from environmental sciences to food industry. Moreover, they can be an answer for the need of novel, less expensive and environmentally neutral methods of analysis particularly in food ingredients assessment.
The aim of this PhD thesis was to develop, optimize and characterize various reporter strains utilizing different signal transducers and targeting carbohydrate constituents of pectin and arabinoxylan. Addit onally, the objective was to assess the potential suitability of microbial biosensors for food ingredients analysis.
Pectin is a plant heteropolysaccharide commonly used in food industry as a gelling agent and food stabilizer. The chemical analysis of the pectin carbohydrate composition is a significant issue during the study of its function and properties. Arabinoxylan is one of the main non-starch polysaccharide derived from the cell wall of cereal grains. It is a dietary fiber, with potential as a functional food ingredient. In this study, reporter strains targeting specifically L-rhamnose, L-arabinose and Dxylose
using three different signal transducers: bioluminescence (luxCDABE), fluorescence (gfp) and ice nucleation (inaZ) were developed. In some cases, due to the unsatisfactory initial signal readings, enhancement of the reporter signal was necessary. In order to achieve that promoter length manipulation method was implemented and proved to be effective. Obtained reporter strains were selective towards respective target analytes and responded quantitatively in selected detection
ranges. Verification of performance of arabinoxylan targeting reporter strains revealed 9-18% difference between the results obtained by biosensors and by High Performance Anion-Exchange Chromatography.
Results of this research suggest that microbial biosensors could be in the future an alternative method for carbohydrate analysis techniques. The use of microbial biosensors is quite simple, costeffective and has a minute environmental impact. Regrettably on this stage of development they cannot be utilized as a reliable tool in food ingredient analysis. Nonetheless, the outcomes of the presented study are promising and indicate great potential of the discussed technology