Fructo-oligosaccharides (FOS) obtained by fermentation of sucrose may be purified at large-scale by continuous chromatography (Simulated Moving Bed: SMB). In order to improve the efficiency of the subsequent SMB purification, the optimization of the fermentative broth composition in salts and sugars was investigated. Fermentations conducted at reduced amount of salts, using Aureobasidium pullulans whole cells, yielded 0.63 ± 0.03 g of FOS per gram of initial sucrose. Additionally, a microbial treatment was proposed to reduce the amount of small saccharides in the mixture. Two approaches were evaluated, namely a co-culture of A. pullulans with Saccharomyces cerevisiae; and a two-step fermentation in which FOS were first synthesized by A. pullulans and then the small saccharides were metabolized by S. cerevisiae. Assays were performed in 100mL shaken flasks and further scaled-up to a 3 L working volume bioreactor. Fermentations in two-step were found to be more efficient than the co-culture ones. FOS were obtained with a purity of 81.6 ± 0.8% (w/w), on a dry weight basis, after the second-step fermentation with S. cerevisiae. The sucrose amount was reduced from 13.5 to 5.4% in total sugars, which suggests that FOS from this culture broth will be more efficiently separated by SMB.

Stevia rebaudiana is known for its sweet-tasting ent-kaurene diterpenoid glycosides. Several manufacturing strategies are currently employed to obtain Stevia sweeteners with the lowest possible off-flavors. The chemical composition of four commercial S. rebaudiana extracts, obtained by different technologies, was characterized using UHPLC-ESI-MS(n). The composition of one of the ethanol-crystallized extracts (EC2) was entirely rebaudioside A, whereas the enzymatically modified (EM) extract contained the lowest concentration of this compound (2.7 mg/100 mg). The membrane-purified (MP) extract had the highest content of minor natural steviol glycosides (23.7 mg/100 mg total extract) versus an average of 2.4 mg/100 mg total extract for the EC samples. Thirteen trained panelists evaluated sweetness, bitterness, licorice, and metallic attributes of all four extracts. The highest licorice intensity (p ≤ 0.05) was found for MP. Both samples EC1 and EC2, despite their different chemical compositions, showed no significant differences in sensory perception.

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Metabolomics aims at gathering the maximum amount of metabolic information for a total interpretation of biological systems. A process analytical technology pipeline, combining gas chromatography-mass spectrometry data preprocessing with multivariate analysis, was applied to a Port wine "forced ageing" process under different oxygen saturation regimes at 60°C. It was found that extreme "forced ageing" conditions promote the occurrence of undesirable chemical reactions by production of dioxane and dioxolane isomers, furfural and 5-hydroxymethylfurfural, which affect the quality of the final product through the degradation of the wine aromatic profile, colour and taste. Also, were found high kinetical correlations between these key metabolites with benzaldehyde, sotolon, and many other metabolites that contribute for the final aromatic profile of the Port wine. The use of the kinetical correlations in time-dependent processes as wine ageing can further contribute to biological or chemical systems monitoring, new biomarkers discovery and metabolic network investigations.

Fructo-oligosaccharides (FOS) are non-digestible sweeteners with improved functional and technological properties for food and pharmaceutical industry applications. The immobilization of FOS-producing microorganism's whole cells can be used to improve the production of FOS and so, an accurate choice of the carrier is of crucial importance. Here we present a screening and selection of carriers for immobilization of Aureobasidium pullulans cells with potential for yielding high FOS production. Synthetic, agro-industrial by-products and mineral materials were tested and selected regarding their ability to immobilize cells, as well as their potential to produce FOS, through shaken-flask fermentations. Increased amounts of immobilized cells were found for carriers with higher porosity observed at the microscope, higher water absorption index (WAI) and lower critical humidity point (CHP). Reticulated polyurethane foam was one of the most efficient synthetic carriers immobilizing cells (over 75% (w/w) of the total cells were immobilized). Also, high FOS production was obtained: FOS concentration, purity and yield increased in 15, 8 and 12% (w/w), respectively, as compared to free cells conditions. Although walnut shell had a much lower immobilization efficiency, the high amount of cells grown while using this carrier led to a highest increment of FOS concentration, purity and yield, namely, 27, 10 and 25% (w/w). Cells immobilization with the selected carriers holds great promise for FOS production on a larger scale.

During must fermentation by Saccharomyces cerevisiae strains thousands of volatile aroma compounds are formed. The objective of the present work was to adapt computational approaches to analyze pheno-metabolomic diversity of a S. cerevisiae strain collection with different origins. Phenotypic and genetic characterization together with individual must fermentations were performed, and metabolites relevant to aromatic profiles were determined. Experimental results were projected onto a common coordinates system, revealing 17 statistical-relevant multi-dimensional modules, combining sets of most-correlated features of noteworthy biological importance. The present method allowed, as a breakthrough, to combine genetic, phenotypic and metabolomic data, which has not been possible so far due to difficulties in comparing different types of data. Therefore, the proposed computational approach revealed as successful to shed light into the holistic characterization of S. cerevisiae pheno-metabolome in must fermentative conditions. This will allow the identification of combined relevant features with application in selection of good winemaking strains.

The production of high-content fructo-oligosaccharides by fermentation in a fed-batch bioreactor is considered. Fed-batch scenario allows to reduce inhibition mechanisms caused by the presence of byproducts, such as glucose, while maximizing biomass production. The determination of the feed flow rate profile that maximizes the concentration of fructo-oligosaccharides is performed by resorting to the maximum principle of Pontryagin. The optimization procedure takes into account inequality constraints on the state and control variables and allows the determination of the unspecified final fermentation time corresponding to maximal fructo-oligosaccharides content. The performance of the approach is demonstrated by simulations in the case of fructo-oligosaccharide production by Aspergillus sp.

Fructo-oligosaccharide (FOS) mixtures produced by fermentation contain large amounts of non-prebiotic sugars. Here we propose a mixed culture of Aureobasidium pullulans and Saccharomyces cerevisiae cells to produce FOS and consume the small saccharides simultaneously, thereby increasing FOS purity in the mixture. The use of immobilised A. pullulans in co-culture with encapsulated S. cerevisiae, inoculated after 10 h fermentation, enhanced FOS production in a 5 L bioreactor. Using this strategy, a maximal FOS concentration of 119 g L −1 , and yield of 0.59 g FOS g sucrose −1 , were obtained after 20 h fermentation, increasing FOS productivity from about 4.9 to 5.9 g FOS L −1 h −1 compared to a control fermentation of immobilized A. pullulans in monoculture. In addition, the encapsulated S. cerevisiae cells were able to decrease the glucose in the medium to about 7.6% (w/w) after 63 h fermentation. This provided a final fermentation mixture with 2.0% (w/w) sucrose and a FOS purity of over 67.0% (w/w). Moreover, a concentration of up to 58.0 g L −1 of ethanol was obtained through the enzymatic transformation of glucose. The resulting pre-purified FOS mixture could improve the separation and purification of FOS in downstream treatments, such as simulated moving bed chromatography.