Synthesis of Oligosaccharides Derived from Lactulose (OsLu) Using Soluble and Immobilized Aspergillus oryzae β-Galactosidase

β-Galactosidase from Aspergillus oryzae offers a high yield for the synthesis of oligosaccharides derived from lactulose (OsLu) by transgalactosylation. Oligosaccharides with degree of polymerization (DP) ≥ 3 have shown to possess higher in vitro bifidogenic effect than di- and tetrasaccharides. Thus, in this work, an optimization of reaction conditions affecting the specific selectivity of A. oryzae β-galactosidase for synthesis of OsLu has been carried out to enhance OsLu with DP ≥ 3 production. Assays with β-galactosidase immobilized onto a glutaraldehyde–agarose support were also carried out with the aim of making the process cost-effective and industrially viable. Optimal conditions with both soluble and immobilized enzyme for the synthesis of OsLu with DP ≥ 3 were 50 °C, pH 6.5, 450 g/L of lactulose, and 8 U/mL of enzyme, reaching yields of ca. 50% (w/v) of total OsLu and ca. 20% (w/v) of OsLu with DP 3, being 6′-galactosyl-lactulose the major one, after a short reaction time. Selective formation of disaccharides, however, was favored at 60 °C, pH 4.5, 450 g/L of lactulose and 8 U/mL of enzyme. Immobilization increased the enzymatic stability to temperature changes and allowed to reuse the enzyme. We can conclude that the use, under determined optimal conditions, of the A. oryzae β-galactosidase immobilized on a support of glutaraldehyde–agarose constitutes an efficient and cost-effective alternative to the use of soluble β-galactosidases for the synthesis of prebiotic OsLu mixturesThis work has been supported by projects AGL2014-53445-R from Ministerio de Economía y Competitividad; ALIBIRD-CM S-2013/ABI-2728 from Comunidad Autónoma de Madrid and COOPB20099 from CSI

Mathematical modeling and forecasting of COVID-19: experience in Santiago de Cuba province

In the province of Santiago de Cuba, Cuba, the COVID-19 epidemic has a limited progression that shows an early small-number peak of infections. Most published mathematical models fit data with high numbers of confirmed cases. In contrast, small numbers of cases make it difficult to predict the course of the epidemic. We present two known models adapted to capture the noisy dynamics of COVID-19 in the Santiago de Cuba province. Parameters of both models were estimated using the approximate-Bayesian-computation framework with dedicated error laws. One parameter of each model was updated on key dates of travel restrictions. Both models approximately predicted the infection peak and the end of the COVID-19 epidemic in Santiago de Cuba. The first model predicted 57 reported cases and 16 unreported cases. Additionally, it estimated six initially exposed persons. The second model forecasted 51 confirmed cases at the end of the epidemic. In conclusion, an opportune epidemiological investigation, along with the low number of initially exposed individuals, might partly explain the favorable evolution of the COVID-19 epidemic in Santiago de Cuba. With the available data, the simplest model predicted the epidemic evolution with greater precision, and the more complex model helped to explain the epidemic phenomenology

Characterization of Galactosyl Derivatives Obtained by Transgalactosylation of Lactose and Different Polyols Using Immobilized beta-Galactosidase from Aspergillus oryzae

The synthesis of novel galactosides is interesting because of their important role in several biological processes. Their properties greatly depend upon the configuration and type of galacto- side. Therefore, to study biological activity, it is essential to elucidate the structure of the products. Glycosidases are capable of catalyzing glycosidic linkages with absolute stereoselectivity of the anomeric center. We report the enzymatic synthesis of galactosyl-ethylene glycol, galactosyl- glycerol, and galactosyl-erythritol by immobilized β-galactosidase from Aspegillus oryzae. The obtained galactosides were isolated and fully characterized by an extensive nuclear magnetic resonance (NMR) study. Complete structure elucidation and full proton and carbon assignments were carried out using 1D (1H and 13C) and 2D (gCOSY, TOCSY, multiplicity-edited gHSQC, and gHMBC) NMR experiments. The β-galactosidase from A. oryzae showed a strong preference for primary alcohols. For galactosyl-glycerol and galactosyl-erythritol, this preference generated one and two chiral centers, respectively, and a mixture of stereoisomers was obtained as a consequence.Peer reviewe