Bioluminescence and ice-nucleation microbial biosensors for l-arabinose content analysis in arabinoxylans

Microbial biosensors are analytical devices converting a biochemical signal into a quantifiable response. Due to their molecular properties, they can be diversely designed in order to fulfill the needs of different fields, from food industry to environmental sciences. One of the possible applications of microbial biosensors concerns arabinoxylans, components of dietary fibers having potential as functional food ingredients, which are also used for biogas production. The aim of this study was to develop reporter strains capable to evaluate the content of l-arabinose monosaccharides in arabinoxylans. The bioluminescent strain DPDaraBAD contains a plasmid in which luxCDABE genes of Photorhabdus luminescens are inserted under the control of Escherichia coli arabinose operon promoter. The ice-nucleation-active strain NIaraBAD bears a similar fusion using the same promoter upstream of the inaZ gene of Pseudomonas syringae. Sufficient response of biosensor cells was obtained after NIaraBAD incubation at 29 A degrees C for 3 h and DPDaraBAD for 6 h, followed by 30-min incubation with l-arabinose. Both reporter strains responded specifically and quantitatively in the presence of the inducer with a detection limit of 0.009 and 0.015 g l(-1), respectively. Validation of reporter strains was performed in comparison with the l-arabinose concentration values obtained by high-performance anion-exchange chromatography (HPAEC) and demonstrated mean divergence of 9.59 % for bioluminescent strain and 15.86 % for ice-nucleation strain, which for microbial sensors is an acceptable dissimilarity. These l-arabinose microbial biosensors can be used as an alternative tool to chromatographic methods in monosaccharide content analysis of arabinoxylans.