Monitoring the composition of fruto-oligosaccharides during transfructosylation reactions by means of infrared spectroscopy

MOBILI P; GOMEZ-ZAVAGLIA A; LIEBEN P; ROMANO N; MARRO M

Caen

Conferencia; 22th Conference of Lactic Acid Bacteria Club; 2019

Lactic Acid Bacteria Club

Fructo-oligosaccharides (FOS) are small chain oligosaccharides composed of fructose units linked by (21)-β-glycosidic bonds and a single D-glucosyl unit at the non-reducing end, that showed to be efficient protectants during freeze-drying and storage of lactic acid bacteria (Romano 2015, 2016a,b, 2018). Their protective mechanism results from a balance between saccharides with low and high degree of polymerization (DP) in the mixtures: the smallest sugars are efficient in protecting lipid membranes by replacing water molecules, and the larger ones favor the formation of vitreous states.FOS can be obtained by transfructosylation reactions using sucrose as substrate. The obtained FOS are mixtures of oligosaccharides with DP from 3 to 5. Considering that the composition of FOS determines their protective capacity during dehydration and storage of lactic acid bacteria, and this composition is determined by the conditions of synthesis, the goals of this work, carried out within the frame of PREMIUM project, were:-to obtain FOS of different DP by adjusting the conditions of synthesis,-to define a model based on multivariate analysis to determine the composition of FOS directly from their FTIR spectra.Matériels et Méthodes/Materials and methodsSyntheses were carried out at 50°C using ViscozymeL as biocatalyst, sucrose (30 and 60 %w/v) as substrate, and 24 hours of reaction time. Samples taken at regular intervals were analyzed by HPLC (reference method) and FTIR. For each sample, eight FTIR spectra were registered in ATR mode (4000-500 cm-1 range) by co-adding 16 scans with 4 cm-1 spectral resolution.Résultats principaux/Main ResultsAround 40 samples were produced using different synthesis conditions. FOS mixtures with different compositions (containing or not monosaccharides), were further characterized.The composition of each sample was determined using a Partial Least Square (PLS) model, calibrated with 240 spectra, and validated with an independent set of data. The mean of predicted values fitted nicely the composition of FOS obtained by HPLC (R2>0.93), thus supporting the use of the PLS model to monitor transfructosylation reactions in situ and in real time.ConclusionConsidering the effect of FOS composition on bacterial stabilization, PREMIUM project will provide strategies for the formulation of specially selected compositions. The possibility of monitoring the composition of FOS directly from the FTIR in situ and in real time represents a useful tool to obtain reliable information with strong economic impact.