Safety considerations of plant polysaccharides for food use: a case study on phenolic-rich softwood galactoglucomannan extract

A growing population and concern over the sufficiency of natural resources for feeding this population has motivated researchers and industries to search for alternative and complementary sources of food ingredients and additives. Numerous plant species and parts of plants are explored as raw materials for food production. An interesting example is wood; to date, few wood-based additives or ingredients are authorized for food use. Wood hemicelluloses, such as softwood galactoglucomannans (GGM), constitute an abundant bioresource that shows a highly potential functionality in edible materials. Spruce GGM—“spruce gum”—acts as a multi-functional emulsion stabilizer, and it could be used in various processed food products, replacing less effective, conventional emulsifiers. Before new materials can be released onto the food market, their safety must be evaluated, according to the Novel Food regulation. This review focuses on the safety aspects that must be considered before polysaccharide- and phenolic-rich plant extracts can be awarded the status of authorized food ingredients. In this review, GGM is presented as a case study and examples are given of plant-based polysaccharides that are already authorized for food purposes. The legislation regarding Novel Food ingredients in Europe is also briefly reviewed.Peer reviewe

The Resistome of Farmed Fish Feces Contributes to the Enrichment of Antibiotic Resistance Genes in Sediments below Baltic Sea Fish Farms

Our previous studies showed that particular antibiotic resistance genes (ARGs) were enriched locally in sediments below fish farms in the Northern Baltic Sea, Finland, even when the selection pressure from antibiotics was negligible. We assumed that a constant influx of farmed fish feces could be the plausible source of the ARGs enriched in the farm sediments. In the present study, we analyzed the composition of the antibiotic resistome from the intestinal contents of 20 fish from the Baltic Sea farms. We used a high-throughput method, WaferGen qPCR array with 364 primer sets to detect and quantify ARGs, mobile genetic elements (MGE), and the 16S rRNA gene. Despite a considerably wide selection of qPCR primer sets, only 28 genes were detected in the intestinal contents. The detected genes were ARGs encoding resistance to sulfonamide (sul1), trimethoprim (dfrA1), tetracycline [tet(32), tetM, tetO, tetW], aminoglycoside (aadA1, aadA2), chloramphenicol (catA1), and efflux-pumps resistance genes (emrB, matA, mefA, msrA). The detected genes also included class 1 integron-associated genes (intI1, qacE?1) and transposases (tnpA). Importantly, most of the detected genes were the same genes enriched in the farm sediments. This preliminary study suggests that feces from farmed fish contribute to the ARG enrichment in farm sediments despite the lack of contemporaneous antibiotic treatments at the farms. We observed that the intestinal contents of individual farmed fish had their own resistome compositions. Our result also showed that the total relative abundances of transposases and tet genes were significantly correlated (p = 0.001, R-2 = 0.71). In addition, we analyzed the mucosal skin and gill filament resistomes of the farmed fish but only one multidrug-efflux resistance gene (emrB) was detected. To our knowledge, this is the first study reporting the resistome of farmed fish using a culture-independent method. Determining the possible sources of ARGs, especially mobilized ARGs, is essential for controlling the occurrence and spread of ARGs at fish farming facilities and for lowering the risk of ARG spread from the farms to surrounding environments.Peer reviewe

Functionality of spruce galactoglucomannans in oil-in-water emulsions

For a sustainable food chain, the demand for plant-based, functional, and cost-effective food hydrocolloids is on a high-rise. Hemicelluloses from the renewable lignocellulosic biomass are available in abundance from side-streams of the forestry industry to fulfill this demand. Their effective valorization requires a safe, economic extraction method that can be up-scaled to an industrial scale and, simultaneously, understanding of their functionality to develop applications. In this study, an aqueous-based extraction method, pressurized hot water extraction (PHWE) of spruce saw meal was used to obtain galactoglucomannans (GGM), "spruce gum". Ethanol precipitation was performed to remove non-polysaccharide extractives such as free phenolic compounds, and the emulsion component ratio-dependent interfacial saturation capacity of the remaining purified fraction was studied to understand its functionality. GGM resulted in good to excellent emulsification and stabilization of oil-in-water emulsions and exhibited adsorption at the oil droplet interface, which depended on the amount of oil and droplet size of emulsions. The adsorbed GGM content was determined by gas chromatography after acid methanolysis, and their macromolecular characteristics were studied by size-exclusion chromatography. At GGM to oil ratios 2, 1, and 0.4, stable emulsions with predicted several months of shelf life at room temperature were achieved. The results indicated mechanisms affecting the physical stabilization and breakdown of emulsions containing spruce gum, a novel sustainable hydrocolloid. (C) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

The Glanville fritillary genome retains ancient karyotype and reveals selective chromosomal fusions in Lepidoptera

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Neural retina limits the nonviral gene transfer to retinal pigment epithelium in an in vitro bovine eye model

We investigated the permeation of liposomal and polymeric gene delivery systems through neural retina into retinal pigment epithelium (RPE) and determined the roles of various factors in permeation and subsequent uptake of the delivery systems by RPE. Anterior parts and vitreous of fresh bovine eyes were removed. Retina was left intact or peeled away. Complexes of ethidium monoazide (EMA)-labeled plasmid DNA and cationic carriers (polyethyleneimine, poly-L-lysine, DOTAP liposomes) were pipetted on the retina or RPE. Two hours later the neural retina was removed, if present, and the RPE cells were detached. Contaminants were removed by sucrose centrifugation, and the RPE cells were analyzed for DNA uptake by flow cytometry. Cellular uptake of FITC-dextrans (molecular weight [mw] 20 000, 500 000 and 2 000 000), FITC-poly-L-lysine (mw 20 000), FITC-labeled oligonucleotide (15-mer), and naked EMA-labeled plasmid DNA was determined after pipetting the solutions on the RPE or neural retina. Location of the fluorescent materials in the retina was visualized with fluorescence microscopy. Neural retina decreased the cellular uptake of DNA complexes by an order of magnitude, the uptake of FITC-dextrans slightly, whereas delivery of polycationic FITC-poly-L-lysine to RPE was almost completely inhibibited. Neural retina decreased the cellular uptake of FITC-oligonucleotides, while the uptake of uncomplexed plasmid was always negligible. conclusions from FACS and fluorescence microscopy were similar: delivery of polymeric and liposomal DNA complexes into RPE are limited by the neural retina. This is due to the size and positive charge of the complexes

Overexpression of NADH-dependent fumarate reductase improves d-xylose fermentation in recombinant Saccharomyces cerevisiae

Deviation from optimal levels and ratios of redox cofactors NAD(H) and NADP(H) is common when microbes are metabolically engineered. The resulting redox imbalance often reduces the rate of substrate utilization as well as biomass and product formation. An example is the metabolism of D-xylose by recombinant Saccharomyces cerevisiae strains expressing xylose reductase and xylitol dehydrogenase encoding genes from Scheffersomyces stipitis. This pathway requires both NADPH and NAD+. The effect of overexpressing the glycosomal NADH-dependent fumarate reductase (FRD) of Trypanosoma brucei in D-xylose-utilizing S. cerevisiae alone and together with an endogenous, cytosol directed NADH-kinase (POS5∆17) was studied as one possible solution to overcome this imbalance. Expression of FRD and FRD + POS5∆17 resulted in 60 and 23 % increase in ethanol yield, respectively, on D-xylose under anaerobic conditions. At the same time, xylitol yield decreased in the FRD strain suggesting an improvement in redox balance. We show that fumarate reductase of T. brucei can provide an important source of NAD+ in yeast under anaerobic conditions, and can be useful for metabolic engineering strategies where the redox cofactors need to be balanced. The effects of FRD and NADH-kinase on aerobic and anaerobic D-xylose and D-glucose metabolism are discussed