No abstract

BACKGROUNDFructooligosaccharides (FOS) are sweeteners produced through the use of enzymes called fructosyltransferases (FTases) (EC 2.4.1.9). However, FTase reuse is meagre and the cost of the enzyme production is high, making FOS production economically unfeasible. In order to address these issues, this study aims to immobilize cells from Aspergillus oryzae IPT‐301, containing FTase enzyme previously glutaraldehyde‐crosslinked, by means of entrapment in calcium alginate beads. The conditions to obtain the particles, such as alginate type, mycelium mechanical dispersion, degree of crosslinking, size of the beads, and their reflections on transfructosylation activity (AT) were evaluated previously.RESULTSThe highest AT used low‐viscosity alginate solution (4.0% w/w) crosslinked with calcium chloride (0.2 mol L−1) and beads of mean diameter 2.15 mm. The entrapment conditions were complemented by conducting the reaction under different temperatures, pH values, substrate concentrations and by reusing the beads. The highest transfructosylation activities were obtained under reaction conditions of 50 °C, pH 5.5 and substrate concentration 400 g L−1.CONCLUSIONThe AT levels found with the glutaraldehyde‐crosslinked and entrapped cells in calcium alginate were ≈70% higher than the ones obtained with free cells, not glutaraldehyde‐crosslinked. Moreover, the immobilized cells (crosslinked+entrapped) retained their AT up to the third cycle of total sucrose depletion in the reaction medium, attesting to the potential use of the beads in continuous FOS production. © 2020 Society of Chemical Industry

No abstract

No abstract

No abstract

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.

No abstract

No abstract