Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

 The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables. Received: 21 May 1997 / Revised version: 10 July 1997     

Thermal properties of doughs formulated with enzymes and starters

 Thermal properties (gelatinization, amylose-lipid complex dissociation and amylopectin retrogradation) of bread samples formulated with two different quality wheat flours, two enzymes (α-amylase/pentosanase, lipase and their mixture), and three microbial sourdough starters were studied with a differential scanning calorimeter. The carbohydrases modified gelatinization temperature and enthalpy, whilst the lipase modified the amylose-lipid complex dissociation. The enthalpy of amylopectin retrogradation was significantly influenced only by the storage of breads. Second-order interactive effects of enzymes with flour or starter were found for gelatinization and/or amylose-lipid complex dissociation parameters. Some interesting relationships were observed between thermal and textural properties of fresh and stored breads. Received: 22 September 1998 / Revised version: 28 October 1998     

生物技术与节能减排——酶在造纸工业中的应用

本文综述了酶在造纸工业中的应用,分别从酶法制浆、酶法脱墨、酶法漂白和废水处理四个方面说明了酶在其中起到的关键作用。在酶法制浆中,说明了漆酶、纤维素酶和半纤维素酶的作用;在酶法脱墨中,说明了纤维素酶和脂肪酶的作用;在酶法漂白中,说明了漆酶和半纤维素酶的作用;在废水处理中,说明了漆酶的作用。     

Some hydrolases in human schistosomiasis with special reference to arylsulfatase B

Among many tested enzymes, lipase was found to be the one most affected by schistosomiasis in human serum, where it is increased eightfold. Arylsulfatases A and B and aspartyl protease displayed a significant decrease in the serum, while other enzymes showed a significant increase. α‐Amylase and Leucine aminopeptidase were significantly increased and arylsulfatase B showed a significant decrease. Arylsulfatase B from a patient's leucocytes did not show either changed kinetic behaviour or temperature‐dependent conformational changes. These results indicate that the diminished activity of this enzyme may be attributed to an opposing mechanism of regulation.     

Early Dissimilar Fates of Liver Eicosapentaenoic Acid in Rats Fed Liposomes or Fish Oil and Gene Expression Related to Lipid Metabolism

The study was undertaken to determine whether eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3), esterified in phospholipids (PL) as liposomes or in triglycerides (TG) as oil, exhibited comparable fates in liver lipids and whether these fates were associated with gene expressions related to fatty acid (FA) metabolism. PL and TG mixtures with close contents in EPA and DHA were administered to rats over 2 weeks. Most relevant events occurred after 3 days for both treatments. At that time, liposomes, compared with oil, increased the liver content in PL with a FA composition enriched in n-6 FA, comparable in DHA and much lower in EPA. Moreover, liposomes increased the activity and mRNA levels of carnitine palmitoyltransferase (CPT) I. In contrast, fish oil exerted opposite effects on CPT I and increased the genic expression of lipogenic enzymes. Liposomes, unlike fish oil, apparently increased the mRNA levels of acyl-CoA oxidase and the activity of the peroxisomal FA-oxidising system. Concomitantly, mRNA levels of hepatic lipoprotein receptors were increased with both diets, but intracellular proteins involved in free FA uptake and lipid synthesis were up-regulated only with liposome-treated rats. The quasi absence of EPA in hepatic PL of liposome-treated rats on the short term could result from increased β-oxidation activities through metabolic regulations induced by more available free EPA and other PUFA.     

Self‐Immobilizing Oxidoreductases for Flow Biocatalysis in Miniaturized Packed‐Bed Reactors

The industrial implementation of enzymes in flow biocatalysis microreactors is expected to be essential for the emergence of a bio‐based circular economy. Major challenges concern the efficient immobilization of delicate enzymes inside miniaturized reactors without compromising their catalytic activity. We describe the exploitation of the widely used His‐tag system in a microfluidic packed‐bed reactor that contains ketoreductase‐functionalized magnetic beads. In a continuous process, these reactors produced highly stereoselective (R)‐configured alcohols (d.r. 99:1) with an average conversion of > 90 % for more than 4 days. We believe that such miniaturized flow reactors can be of great utility for future sustainable production processes.     

Creep of the eye sclera

 Irreversible stretching (creep) of the eye sclera, considered as a cause of the high myopia, has been studied experimentally. Both dramatic acceleration and significant deceleration of the sclera creep have been observed in the presence of some enzymes. Creep of various connective tissues caused by static and cyclic mechanical stresses (gravity, blood pressure, etc.) can manifest in many age and pathological changes in human body. Authors express the hope that investigations in this area and finding appropriate inhibitors may replace surgery (eye, cosmetic) by prophylactic therapy. Received: 21 July 1998 / Accepted: 28 August 1998     

Glycosidases of wheat

Glycosidases isolated from the mill fractions made from soft and hard wheat grists were studied. α-Arabinosidase, α-galactosidase, β-galactosidase, β-glucosidase, β-glucuronidase, β-mannosidase and β-xylosidase activities in wheat flour, germ and bran were determined under standard dough conditions. There were no significant differences between the level of glycosidase activities from hard and soft grists. The level of a particular glycosidase activity was generally highest in the germ and lowest in the flour.     

Evaluation of pectolytic activities of enological interest in industrial enzyme preparations

 The purpose of this research was to determine the activity of several pectolytic enzymes, such as pectin methyl esterase, endopolymethylgalacturonase, endopolygalacturonase, exopolymethylgalacturonase, endopolygalacturonase, pectin transeliminase and pectic acid transeliminase, from within preparations that are available on the Portuguese market. The selected preparations were as follows: 15 pectolytic enzyme preparations, one hemicellulolytic preparation and one glucanase preparation. The measurements of enzyme activity were carried out using model solutions with 50 mg·l^–1 SO₂, pH 3.2, 25°C, with and without 12% ethanol (v/v), and a 24-h incubation period. Quantitatively, the results proved to be heterogeneous, significantly varying from preparation to preparation: all pectolytic enzyme activities in the 17 preparations analysed in this study were significantly different. The presence of ethanol reduced the enzymatic activity, apart from that of endopolymethylgalacturonase, and, in general, an increase of enzyme concentration raised the pectolytic enzyme activity. Received: 17 March 1997 / Revised version: 11 June 1997