Hypocholesterolemic Effect of the Lignin-Rich Insoluble Residue of Brewer's Spent Grain in Mice Fed a High-Fat Diet.

Insoluble residue (INS) is a lignin-rich fraction of brewer's spent grain (BSG) that also contains β-glucan and arabinoxylan, the major constituents of dietary fiber. We investigated the effects of INS in diet-induced obese mice in terms of lipid metabolism and metabolic diseases. Male mice (C57bl6) were fed a high-fat diet (HFD), a HFD + 20% INS, a HFD + 20% cellulose (CEL), a HFD with a combination of 20% INS-CEL (1:1), or a control diet for 14 weeks.

Characterization of sulfhydryl oxidase from Aspergillus tubingensis.

Background: Despite of the presence of sulfhydryl oxidases (SOXs) in the secretomes of industrially relevant organisms and their many potential applications, only few of these enzymes have been biochemically characterized. In addition, basic functions of most of the SOX enzymes reported so far are not fully understood. In particular, the physiological role of secreted fungal SOXs is unclear.

Interactions of Insoluble Residue from Enzymatic Hydrolysis of Brewer's Spent Grain with Intestinal Microbiota in Mice.

Brewer's spent grain (BSG) is the major side-stream from brewing. As BSG is rich in dietary fiber and protein, it could be used in more valuable applications, such as nutritional additives for foods. Our aim was to elucidate whether an insoluble lignin-rich fraction (INS) from BSG is metabolized by mice gut microbiota and how it affects the microbiota.

Structure of Brewer's Spent Grain Lignin and Its Interactions with Gut Microbiota in Vitro.

Lignin is part of dietary fiber, but its conversion in the gastrointestinal tract is not well understood. The aim of this work was to obtain structural information on brewer's spent grain (BSG) lignin and to understand the behavior of the polymeric part of lignin exposed to fecal microbiota. The original BSG and different lignin fractions were characterized by pyrolysis-GC/MS with and without methylation.

Industrial potential of lipoxygenases.

Lipoxygenases (LOXs) are iron- or manganese-containing oxidative enzymes found in plants, animals, bacteria and fungi. LOXs catalyze the oxidation of polyunsaturated fatty acids to the corresponding highly reactive hydroperoxides. Production of hydroperoxides by LOX can be exploited in different applications such as in bleaching of colored components, modification of lipids originating from different raw materials, production of lipid derived chemicals and production of aroma compounds.

Sensitizing potential of enzymatically cross-linked peanut proteins in a mouse model of peanut allergy.

Scope: The cross-linking of proteins by enzymes to form high-molecular-weight protein, aggregates can be used to tailor the technological or physiological functionality of food products. Aggregation of dietary proteins by food processing may promote allergic sensitization, but the effects of enzymatic cross-linking of dietary proteins on the allergenic potential of food are not known. In this study, the bioavailability and the sensitizing or tolerizing potential of peanut proteins (PE) cross-linked with microbial tyrosinase from Trichoderma reesei and mushroom tyrosinase from Agaricus bisporus, were investigated.

Release of small phenolic compounds from brewer's spent grain and its lignin fractions by human intestinal microbiota in vitro.

Brewer's spent grain (BSG), the major side-stream from brewing, is rich in protein, lignin, and nonstarch polysaccharides. Lignin is a polyphenolic macromolecule considered resilient toward breakdown and utilization by colon microbiota, although some indications of release of small phenolic components from lignin in animals have been shown. The aim of this study was to investigate if the human intestinal microbiota can release lignans and small phenolic compounds from whole BSG, a lignin-enriched insoluble fraction from BSG and a deferuloylated fraction, in a metabolic in vitro colon model.

Interactions of a lignin-rich fraction from brewer's spent grain with gut microbiota in vitro.

Lignin is a constituent of plant cell walls and thus is classified as part of dietary fiber. However, little is known about the role of lignin in gastrointestinal fermentation. In this work, a lignin-rich fraction was prepared from brewer's spent grain and subjected to an in vitro colon model to study its potential bioconversions and interactions with fecal microbiota.

Pre-hydrolysis with carbohydrases facilitates the release of protein from brewer's spent grain.

Brewer's spent grain (BSG) is the most abundant side-stream from brewing. It is food-grade being rich in dietary fibre and protein and thus having potential as their source for both food and non-food applications. Initial treatment of milled BSG with a carbohydrase cocktail from Humicola insolens significantly enhanced the subsequent solubilisation of protein from the residual biomass.

Screening of microbes for novel acidic cutinases and cloning and expression of an acidic cutinase from Aspergillus niger CBS 513.88.

Isolates from gardening waste compost and 38 culture collection microbes were grown on agar plates at pH 4.0 with the cutinase model substrate polycaprolactone as a carbon source. The strains showing polycaprolactone hydrolysis were cultivated in liquid at acidic pH and the cultivations were monitored by assaying the p-nitrophenyl butyrate esterase activities.

Discovery of novel secreted fungal sulfhydryl oxidases with a plate test screen.

Sulfhydryl oxidases (SOX) are FAD-dependent enzymes capable of oxidising free thiol groups and forming disulphide bonds. Although the quantity of scientific papers and suggested applications for SOX is constantly increasing, only a limited number of microbial SOX have been reported and are commercially available. Hence, the aim of this study was to develop a fast and reliable qualitative plate test for screening novel secreted fungal SOX.

Characterization of lipids and lignans in brewer's spent grain and its enzymatically extracted fraction.

Brewer's spent grain (BSG), the major side stream of brewing, consists of the husks and the residual parts of malts after the mashing process. BSG was enzymatically fractionated by a two-step treatment with carbohydrate- and protein-degrading enzymes, which solubilized 66% of BSG. BSG contained 11% lipids, which were mostly triglycerides, but also a notable amount of free fatty acids was present.

Impact of cell wall-degrading enzymes on water-holding capacity and solubility of dietary fibre in rye and wheat bran.

Background: Rye and wheat bran were treated with several xylanases and endoglucanases, and the effects on physicochemical properties such as solubility, viscosity, water-holding capacity and particle size as well as the chemical composition of the soluble and insoluble fractions of the bran were studied. A large number of enzymes with well-defined activities were used. This enabled a comparison between enzymes of different origins and with different activities as well as a comparison between the effects of the enzymes on rye and wheat bran.

Transglutaminase catalyzed cross-linking of sodium caseinate improves oxidative stability of flaxseed oil emulsion.

Sodium caseinate was modified by transglutaminase catalyzed cross-linking reaction prior to the emulsification process in order to study the effect of cross-linking on the oxidative stability of protein stabilized emulsions. The extent of the cross-linking catalyzed by different dosages of transglutaminase was investigated by following the ammonia production during the reaction and using SDS-PAGE gel. O/W emulsions prepared with the cross-linked and non-cross-linked sodium caseinates were stored for 30 days under the same conditions.

Effect of a milling pre-treatment on the enzymatic hydrolysis of carbohydrates in brewer's spent grain.

Millions of tonnes of brewer's spent grain (BSG) are annually produced worldwide as a by-product of the brewing industry. BSG has the potential to be a valuable source of food, chemicals and energy if cost-efficient fractionation methods can be developed. A 2-fold improvement in carbohydrate solubilisation could be achieved through the introduction of a milling step prior to enzymatic hydrolysis.

Methods for identifying lipoxygenase producing microorganisms on agar plates.

Plate assays for lipoxygenase producing microorganisms on agar plates have been developed. Both potassium iodide-starch and indamine dye formation methods were effective for detecting soybean lipoxygenase activity on agar plates. A positive result was also achieved using the β-carotene bleaching method, but the sensitivity of this method was lower than the other two methods.

Extracellular tyrosinase from the fungus Trichoderma reesei shows product inhibition and different inhibition mechanism from the intracellular tyrosinase from Agaricus bisporus.

Tyrosinase (EC 1.14.18.

Loosening of globular structure under alkaline pH affects accessibility of β-lactoglobulin to tyrosinase-induced oxidation and subsequent cross-linking.

Globular proteins such as β-lactoglobulin (BLG) are poorly accessible to enzymes. We have studied susceptibility of BLG to oxidation by Trichoderma reesei (TrTyr) and Agaricus bisporus (AbTyr) tyrosinases and subsequent intermolecular cross-linking with respect to pH-induced structural changes. We evaluated pH-induced structural changes in BLG using circular dichroism, tryptophan fluorescence and small angle X-ray scattering (SAXS) measurements, where after these results were correlated with the analysis of cross-linking by sodium dodecyl sulphate polyacrylamide gel electrophoresis.

One-step method for isolation and purification of native β-lactoglobulin from bovine whey.

Background: The major whey protein β-lactoglobulin (BLG) has been widely studied for its functional properties. The aim of this study was to develop an efficient, inexpensive and rapid one-step method for the isolation and purification of BLG while preserving its native structure.

Results: BLG was purified from defatted whey obtained from raw cow's milk by anion exchange chromatography.

Charge modifications to improve the emulsifying properties of whey protein isolate.

Whey protein isolate was modified by ethylene diamine in order to shift its isoelectric point to an alkaline pH. The extent of the modification was studied using SDS-PAGE and MALDI-TOF mass spectrometry. The modified whey proteins were used as an emulsifier to stabilize oil-in-water emulsions at acidic and neutral pH ranges, and their emulsifying properties were compared with that of the unmodified whey proteins and with the previously studied ethylene diamine modified sodium caseinate.

Effects of tyrosinase and laccase on oat proteins and quality parameters of gluten-free oat breads.

Effects of a Trichoderma reesei tyrosinase (TYR) and a Trametes hirsuta laccase (LAC) on breadmaking performance of gluten-free oat flour were investigated by SDS-PAGE analysis of oat protein fractions, large deformation rheology, and microscopy of the doughs, as well as on the basis of specific volume and firmness of the gluten-free breads. TYR induced the formation of higher molecular weight proteins in the SDS-PAGE assay. Microscopical analysis showed more intensive protein aggregation in the TYR-treated dough than in the dough without TYR.

Sulfhydryl oxidases: sources, properties, production and applications.

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but also secreted SOXs are known.

Production and characterisation of AoSOX2 from Aspergillus oryzae, a novel flavin-dependent sulfhydryl oxidase with good pH and temperature stability.

Sulfhydryl oxidases have found application in the improvement of both dairy and baking products due to their ability to oxidise thiol groups in small molecules and cysteine residues in proteins. A genome mining study of the available fungal genomes had previously been performed by our group in order to identify novel sulfhydryl oxidases suitable for industrial applications and a representative enzyme was produced, AoSOX1 from Aspergillus oryzae (Faccio et al. BMC Biochem 11:31, 2010).

Improving laccase catalyzed cross-linking of whey protein isolate and their application as emulsifiers.

Whey protein isolate (WPI) was chemically modified by vanillic acid in order to enhance its cross-linkability by laccase enzyme. Incorporation of methoxyphenol groups created reactive sites for laccase on the surface of the protein and improved the efficiency of cross-linking. The vanillic acid modified WPI (Van-WPI) was characterized using MALDI-TOF mass spectrometry, and the laccase-catalyzed cross-linking of Van-WPI was studied.

Protein analysis by 31p NMR spectroscopy in ionic liquid: quantitative determination of enzymatically created cross-links.

Cross-linking of β-casein by Trichoderma reesei tyrosinase (TrTyr) and Streptoverticillium mobaraense transglutaminase (Tgase) was analyzed by (31)P nuclear magnetic resonance (NMR) spectroscopy in ionic liquid (IL). According to (31)P NMR, 91% of the tyrosine side chains were cross-linked by TrTyr at high dosages. When Tgase was used, no changes were observed because a different cross-linking mechanism was operational.