Proceedings of International Congress on Bioactive Compounds and International Workshop on Bioactive Compounds
Proceedings of 1st International Congress on Bioactive Compounds and 2nd International Workshop on Bioactive Compounds - Vol. 1 - 2018

Introduction
Wheat bran, the main byproduct of flour production, is composed by a set of residues with different particle sizes named wheat middlings, fine and coarse wheat bran. The bioactive compounds as well as the dietary fiber content found in wheat bran have been associated with several beneficial properties to human health. Prebiotic compounds are substrates not metabolized by host enzymes, but by its microbiota, providing health benefits. Xylooligosaccharides (XOS) are emerging prebiotics derived from arabinoxylans, which are polysaccharides present in cereals.
Objectives
This study aimed to characterize and quantify the produced XOS from the bioprocessing of wheat middlings, using a probiotic Bacillus subtilis strain, during the 72h cultivation.
Methods
The 5% wheat middlings solution was autoclaved, then inoculated with B. subtilis FTC01 at a concentration of 108 CFU/mL and incubated at 37°C for 72h at 125 rpm. Aliquots were collected after inoculation (time 0) and 12, 24, 36, 48, and 72h of cultivation, then centrifuged at 10000g for 15 min at 4°C, filtered by 0.22 µm membranes and frozen at -20°C. The yield and identification of XOS and xylose content of samples were determined using a liquid chromatograph with a refractive index detector. Xylose (X1) and XOS (X2, X3, X4 and X5) were used as reference standards by preparing calibration curves.
Results and Discussion
With respect to the profile, control sample showed the presence of xylose and XOS with degree of polymerization (DP) between 2 and 4, whereas XOS with higher DP (4-5) were present in greater amount after 36h of bioprocessing. Xylopentose (X5) appears to be three times more concentrated in 72h than in 12h of cultivation and was not even identified in control sample. Xylotriose (X3) and xylotetrose (X4) were present in higher concentrations in the 48h of bacterial bioprocessing sample. However, xylobiose (X2) and xylose (X1) were found in low amount, where the bioprocessed samples had lower concentrations than control. Those differences are probably because the B. subtilis FTC01 is continuously producing xylanolytic enzymes, but also consuming the sugars. The presence of xylose in control samples may be caused by the autoclaving pretreatment. Regarding the total amount of the analyzed sugars, calculated by the sum of the concentrations for each sample and each sugar, the XOS with the highest concentration found was X3 (3.13 mg/mL) and the sample was that one bioprocessed for 48h (3.25 mg/mL). Although the presence of xylose in the medium is not desirable, since it is not prebiotic, this sugar is fermentable and can be converted into xylitol, a natural sweetener used as sucrose substitute.
Conclusions
Wheat middlings appears to be a good substrate for production of prebiotic compounds like XOS. The profile and concentration of those oligosaccharides varied considerably between control and bioprocessed samples and among these at different culture times. B. subtilis FTC01 appears to be a great source of xylanolytic enzymes, and its use for bioprocessing the wheat middlings was able to improve this waste material by given it potential prebiotic claims and value-added.