Glucosyltransferase activities, produced by batch culture of Leuconostoc mesenteroides NRRL B-1299, were recovered both in the culture supernatant (SGT) and associated with the insoluble part of the culture (IGT). A total glucosyltransferase activity of 3.5 U/mL was measured in batch culture. The enzymes from the supernatant were purified 313 times using aqueous two-phase partition between dextran and PEG phases, yielding a preparation with 18.8 U/mg protein. It was shown that both SGT and IGT preparations catalyze acceptor reactions and transfer the glucose unit from sucrose onto maltose to produce glucooligosaccharides. Some of the glucooligosaccharides synthesized (Ln series) contain alpha-(1-->6) osidic linkages and a maltose residue at the reducing end. They were completely hydrolyzed by glucoamylase and dextranase. The other glucooligosaccharides synthesized (Bn series) resisted the action of these enzymes. The tetrasaccharide of this series has been characterized by 13C NMR. Its structure was determined as 2-O-alpha-D-glucosylpanose. The oligosaccharides synthesized by the maltose acceptor reaction with the SGT and IGT preparations only differed in the relative amounts in which they were produced. The difference may arise from diffusional limitations appearing when the insoluble catalyst is used. Under the assay conditions, the glucanase resistant oligosaccharide yield was 35% with both glucosyltransferase preparations.
Glucovanillin was extracted from green pods and simultaneously transformed to vanillin by a combination of enzyme activities involving cell wall degradation and glucovanillin hydrolysis. The reaction is best carried out with 47.5% v/v aqueous ethanol solution during 8 h at 70 degrees C, in a two-step enzymatic reaction using Viscozyme followed by Celluclast, two commercial enzymatic products containing mainly pectinase and cellulase activities, respectively. The extractive reaction proceeded with high efficiency with an amount of extracted vanillin 3.13 times higher than the one obtained with the Soxhlet method. The classical curing/extraction process results in 1.1-1.8 g of vanillin/100 g of dry pods. It is concluded that the enzymatic reaction may substitute the microbial process involved in tissue fermentation previous to vanillin extraction with the simultaneous hydrolysis of glucovanillin.
A modification of the process of oil extraction from rice bran is proposed, introducing one or two enzymatic reactions previous to solvent extraction. Although a total aqueous enzymatic extraction process did not result in reasonable oil extraction yields, an interesting alternative results from enzymatic reactions previous to solvent extraction or pressing. A thermal treatment of rice bran is first applied to deactivate lipase, but also to gelatinize starch previous to reaction with α‐amylase. This is followed by a saccharifying step with glucoamylase to produce glucose (28 g/100 g of rice bran treated), while the residual paste, 66.7% of the original bran, may be subjected to a proteolytic process for protein extraction or directly treated with the solvent to obtain bran oil. Finally, under the defined extraction conditions using hexane, yields of oil are 5% higher when rice bran has been previously treated with α‐amylase.
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