Influence of heat treatments on the functionality of soy protein hydrolysates in animal cell cultures.

Soy protein hydrolysates enhance integral viable cell density (IVCD) and recombinant protein production (Immunoglobulin, IgG) in cell cultures, but their functionality varies from batch-to-batch. This is undesirable since it affects both quantity and characteristics of the recombinant proteins. It is hypothesized that the variability of hydrolysates is due to variations in meal and hydrolysate processing treatments. To study this, hydrolysates were produced from meals heated at 121 °C/0-120 min. The heating decreased free amino acid and reducing monosaccharide contents in meals (0.72-0.27% and 3.3-2.6%) and hydrolysates (14.7-7.1% and 16.9-7.9%). Dry heating introduced large variation in the IVCD ((115-316%), but additional heating in suspension reduced it (131-159%). The decrease in IVCD variation corresponded with decreased variation in carboxymethyl-lysine (CML) and lysinoalanine (LAL) contents. Thus, meal and hydrolysate processing induced substantial variation in hydrolysate functionality. It is therefore critical to establish strict process controls for meal and hydrolysate production to ensure consistency.

Modulation of Glucosinolate Composition in Brassicaceae Seeds by Germination and Fungal Elicitation.

Glucosinolates (GSLs) are of interest for potential antimicrobial activity of their degradation products and exclusive presence in Brassicaceae. Compositional changes of aliphatic, benzenic, and indolic GSLs of Sinapis alba, Brassica napus, and B. juncea seeds by germination and fungal elicitation were studied. Rhizopus oryzae (nonpathogenic), Fusarium graminearum (nonpathogenic), and F. oxysporum (pathogenic) were employed. Thirty-one GSLs were detected by reversed-phase ultrahigh-performance liquid chromatography photodiode array with in-line electrospray ionization mass spectrometry (RP-UHPLC-PDA-ESI-MSn). Aromatic-acylated derivatives of 3-butenyl GSL, p-hydroxybenzyl GSL, and indol-3-ylmethyl GSL were for the first time tentatively annotated and confirmed to be not artifacts. For S. alba, germination, Rhizopus elicitation, and F. graminearum elicitation increased total GSL content, mainly consisting of p-hydroxybenzyl GSL, by 2-3 fold. For B. napus and B. juncea, total GSL content was unaffected by germination or elicitation. In all treatments, aliphatic GSL content was decreased (≥50%) in B. napus and remained unchanged in B. juncea. Indolic GSLs were induced in all species by germination and nonpathogenic elicitation.

Effect of oat and soybean rich in distinct non-starch polysaccharides on fermentation, appetite regulation and fat accumulation in rat.

Consumption of non-starch polysaccharides (NSP) is associated with reduced risk of obesity. This study aimed to compare the effects of cereals (oats) and legumes (soybean), rich in different classes of NSP, on appetite regulation and fat accumulation in rats. Soy pectin fermented more efficient than cereal arabinoxylan in rats. Soy pectin and oat ß-glucan were utilized mainly in the caecum of rats. Only small amount of maltodextrin, cello-oligosaccharides and xylo-oligosaccharides were detected in the digesta. Caecal fermentation of soy pectin produced significantly higher concentration of short chain fatty acids (SCFAs) compared to the control. Retroperitoneal (RP) fat-pad weight was significantly lower for rats fed with soybean meal enriched diet than for controls. An inverse correlation between rat RP fat-pad weight and concentration (and proportion) of butyrate was observed. Consumption of soy pectin and oat ß-glucan enriched foods to produce targeted SCFAs in vivo could be a potential strategy to lower fat mass accumulation and a potential tool to manage obesity.

Maillard induced aggregation of individual milk proteins and interactions involved.

The aggregation of α-lactalbumin, ß-lactoglobulin and ß-casein after heating in dry state was studied in absence and presence of saccharides. In absence of saccharides, differences were observed in the extent of aggregation. Differences between the proteins were mostly due to differences in covalent aggregation. The presence of glucose during the heat treatment of milk proteins significantly increased the extent of aggregation, and decreased differences between proteins. α-Lactalbumin was selected as a model protein for the study of cross-links formed after heat treatment. In the presence of saccharides, these cross-links were found to consist of 36% of disulphide bridges (compared to >75% in the absence of glucose), followed by other cross-links such as lanthionine. Larger saccharides led to a decrease in Maillard induced aggregation; maltotriose actually even inhibited the formation of α-lactalbumin aggregates.

Mass spectrometric characterisation of avenanthramides and enhancing their production by germination of oat (Avena sativa).

Avenanthramides are amides, with a phenylalkenoic acid (PA) and an anthranilic acid (AA) subunit, which are secondary metabolites of oat. Oat seeds were germinated, extracted, and the avenanthramides analysed by a combination of UHPLC with ion trap and high resolution ESI-MS. Typical fragmentation pathways with corresponding diagnostic fragments belonging to the PA and AA subunits were identified and summarised in a decision guideline. Based on these findings 28 unique avenanthramides were annotated in the oat seed(ling) extracts, including the new avenanthramide 6f (with a 4/5-methoxy AA subunit). Avenanthramide content increased by 25 times from seed to seedling. Avenanthramides 2p, 2c, and 2f, which are commonly described as the major avenanthramides, represented less than 20% of the total content in the seedlings. Future quantitative analyses should, therefore, include a wider range of avenanthramides to avoid underestimation of the total avenanthramide content.

QSAR of 1,4-benzoxazin-3-one antimicrobials and their drug design perspectives.

Synthetic derivatives of 1,4-benzoxazin-3-ones have been shown to possess promising antimicrobial activity, whereas their natural counterparts were found lacking in this respect. In this work, quantitative structure-activity relationships (QSAR) of natural and synthetic 1,4-benzoxazin-3-ones as antimicrobials were established. Data published in literature were curated into an extensive dataset of 111 compounds. Descriptor selection was performed by a genetic algorithm. QSAR models revealed differences in requirements for activity against fungi, gram-positive and gram-negative bacteria. Shape, VolSurf, and H-bonding property descriptors were frequently picked in all models. The models obtained for gram-positive and gram-negative bacteria showed good predictive power (Q2Ext 0.88 and 0.85, respectively). Based on the models generated, an additional set of 1,4-benzoxazin-3-ones, for which no antimicrobial activity had been determined in literature, were evaluated in silico. Additionally, newly designed lead compounds with a 1,4-benzoxazin-3-one scaffold were generated in silico by varying the positions and combinations of substituents. Two of these were predicted to be up to 5 times more active than any of the compounds in the current dataset. The 1,4-benzoxazin-3-one scaffold was concluded to possess potential for the design of new antimicrobial compounds with potent antibacterial activity, a multitarget mode of action, and possibly reduced susceptibility to gram negatives' efflux pumps.

Structure Dependent-Immunomodulation by Sugar Beet Arabinans via a SYK Tyrosine Kinase-Dependent Signaling Pathway.

There is much interest in the immunomodulatory properties of dietary fibers but their activity may be influenced by contamination with microbial-associated molecular patterns (MAMPs) such as lipopolysaccharide (LPS) and lipoteichoic acids, which are difficult to remove completely from biological samples. Bone marrow-derived dendritic cells (BMDCs) from TLR2x4 double-KO mice were shown to be a reliable approach to analyse the immunomodulatory properties of a diverse range of dietary fibers, by avoiding immune cell activation due to contaminating MAMPs. Several of the 44 tested dietary fiber preparations induced cytokine responses in BMDCs from TLR2x4 double-KO mice. The particulate fractions of linear arabinan (LA) and branched arabinan (BA) from sugar beet pectin were shown to be strongly immune stimulatory with LA being more immune stimulatory than BA. Enzymatic debranching of BA increased its immune stimulatory activity, possibly due to increased particle formation by the alignment of debranched linear arabinan. Mechanistic studies showed that the immunostimulatory activity of LA and BA was independent of the Dectin-1 recognition but Syk kinase-dependent.

Structure and biosynthesis of benzoxazinoids: Plant defence metabolites with potential as antimicrobial scaffolds.

Benzoxazinoids, comprising the classes of benzoxazinones and benzoxazolinones, are a set of specialised metabolites produced by the plant family Poaceae (formerly Gramineae), and some dicots. The family Poaceae in particular contains several important crops like maize and wheat. Benzoxazinoids play a role in allelopathy and as defence compounds against (micro)biological threats. The effectivity of benzoxazinones in these functionalities is largely imposed by the subclasses (determined by N substituent). In this review, we provide an overview of all currently known natural benzoxazinoids and a summary of the current state of knowledge of their biosynthesis. We also evaluated their antimicrobial activity based on minimum inhibitory concentration (MIC) values reported in literature. Monomeric natural benzoxazinoids seem to lack potency as antimicrobial agents. The 1,4-benzoxazin-3-one backbone, however, has been shown to be a potential scaffold for designing new antimicrobial compounds. This has been demonstrated by a number of studies that report potent activity of synthetic derivatives of 1,4-benzoxazin-3-one, which possess MIC values down to 6.25 µg mL-1 against pathogenic fungi (e.g. C. albicans) and 16 µg mL-1 against bacteria (e.g. S. aureus and E. coli). Observations on the structural requirements for allelopathy, insecticidal, and antimicrobial activity suggest that they are not necessarily conferred by similar mechanisms.

Apparent ileal digestibility of Maillard reaction products in growing pigs.

The absorption of Maillard reaction products (MRP) from dietary origin has been linked to the occurrence of chronic diseases. The aim of the present study was to determine the effects of toasting time of rapeseed meal (RSM) and the processing method of the diets (pelleting and extrusion) that included RSM on the apparent ileal digestibility (AID) of total lysine, fructosyl-lysine (FL), carboxymethyl-lysine (CML), carboxyethyl-lysine (CEL), lanthionine (LAN) and lysinoalanine (LAL) in growing pigs. The study consisted of a 2×3 factorial design with toasting time of RSM (60, 120 min) and diet processing method (mash, pelleted, extruded) as factors. Fifty growing pigs were individually fed one of the experimental diets for 4.5 consecutive days. Following euthanasia, samples of digesta were collected from the terminal 1.5 m of the small intestine. Increasing the toasting time of RSM increased the contents of FL, CML and CEL, whereas the additional effects of the diet processing methods were relatively small. Lysinoalanine and lanthionine were not detected in the diets; therefore, digestibility of these compounds could not be determined. The contents of FL, CML and CEL in the ileal chyme were positively correlated to their contents in the diets. The AID of the MRP from thermally-treated RSM were overall low and were not related to their contents in the diets. The AID of FL ranged between -8.5 and 19.1%, whilst AID of CML and CEL ranged from -0.2 to 18.3 and 3.6 to 30%, respectively. In conclusion, thermal treatments have clear effects on the contents of MRP in the diets. These compounds have relatively low digestibility in growing pigs.

QSAR-based molecular signatures of prenylated (iso)flavonoids underlying antimicrobial potency against and membrane-disruption in Gram positive and Gram negative bacteria.

Prenylated flavonoids and isoflavonoids are phytochemicals with remarkable antibacterial activity. In this study, 30 prenylated (iso)flavonoids were tested against Listeria monocytogenes and Escherichia coli (the latter in combination with an efflux pump inhibitor). Minimum inhibitory concentrations of the most active compounds ranged between 6.3-15.0 µg/mL. Quantitative structure-activity relationships (QSAR) analysis was performed and linear regression models were proposed with R2 between 0.77-0.80, average R2m between 0.70-0.75, Q2LOO between 0.66-0.69, and relatively low amount of descriptors. Shape descriptors (related to flexibility and globularity), together with hydrophilic/hydrophobic volume and surface area descriptors, were identified as important molecular characteristics related to activity. A 3D pharmacophore model explaining the effect of the prenyl position on the activity of compounds was developed for each bacterium. These models predicted active compounds with an accuracy of 71-88%. With regard to the mode of action, good antibacterial prenylated (iso)flavonoids with low relative hydrophobic surface area caused remarkable membrane permeabilization, whereas those with higher relative hydrophobic surface area did not. Based on the QSAR and membrane permeabilization studies, the mode of action of antibacterial prenylated (iso)flavonoids was putatively rationalized.

Comparison of Protein Hydrolysis Catalyzed by Bovine, Porcine, and Human Trypsins.

Based on trypsin specificity (for lysines and arginines), trypsins from different sources are expected to hydrolyze a given protein to the same theoretical maximum degree of hydrolysis (DHmax,theo). This is in contrast with experiments. Using α-lactalbumin and ß-casein, this study aims to reveal if the differences among experimental DHmax (DHmax,exp) by bovine, porcine, and human trypsins are due to their secondary specificity. Peptide analysis showed that ∼78% of all the cleavage sites were efficiently hydrolyzed by porcine trypsin, and ∼47 and ∼53% were efficiently hydrolyzed by bovine and human trypsins, respectively. These differences were explained by the enzyme secondary specificity, that is, their sensitivities to the amino acids around the cleavage sites. The DHmax predictions based on the secondary specificity were 4 times closer to the DHmax,exp than the predictions based on trypsin specificity alone (DHmax,theo). Proposed preliminary relations between binding sites and trypsin secondary specificity allow DHmax,exp estimations of tryptic hydrolysis of other proteins.

Maillard induced glycation behaviour of individual milk proteins.

This paper set out to differentiate the Maillard induced glycation reactivity of individual milk proteins using different saccharides under well-defined reaction conditions. α-Lactalbumin, ß-lactoglobulin and ß-casein were incubated with mono-, di- and trisaccharides in the dry state under standardised buffered conditions and glycation was expressed relative to the available reactive groups per protein (DG). Protein reactivity, described by the DGmax and initial speed of glycation (v), followed the same order for each protein-saccharide incubation: α-lactalbumin > ß-lactoglobulin ≫ ß-casein. Glycation of whey proteins by different monosaccharides was double that of ß-casein. Differences in DG between whey proteins and ß-casein decreased with increased saccharide size. A two-fold difference was found for glycation in the presence of the dimers lactose and maltose for ß-casein but not for the whey proteins. The percentage of glycated lysines increased with increased lysine to protein size ratio.

Laccase/Mediator Systems: Their Reactivity toward Phenolic Lignin Structures.

Laccase-mediator systems (LMS) have been widely studied for their capacity to oxidize the nonphenolic subunits of lignin (70-90% of the polymer). The phenolic subunits (10-30% of the polymer), which can also be oxidized without mediators, have received considerably less attention. Consequently, it remains unclear to what extent the presence of a mediator influences the reactions of the phenolic subunits of lignin. To get more insight in this, UHPLC-MS was used to study the reactions of a phenolic lignin dimer (GBG), initiated by a laccase from Trametes versicolor, alone or in combination with the mediators HBT and ABTS. The role of HBT was negligible, as its oxidation by laccase occurred slowly in comparison to that of GBG. Laccase and laccase/HBT oxidized GBG at a comparable rate, resulting in extensive polymerization of GBG. In contrast, laccase/ABTS converted GBG at a higher rate, as GBG was oxidized both directly by laccase but also by ABTS radical cations, which were rapidly formed by laccase. The laccase/ABTS system resulted in Cα oxidation of GBG and coupling of ABTS to GBG, rather than polymerization of GBG. Based on these results, we propose reaction pathways of phenolic lignin model compounds with laccase/HBT and laccase/ABTS.

Rapid membrane permeabilization of Listeria monocytogenes and Escherichia coli induced by antibacterial prenylated phenolic compounds from legumes.

Prenylated phenolics from the Fabaceae are promising lead compounds for new antibacterials. Pools enriched in prenylated phenolics were made from lupine, peanut and soybean seedlings. One pool was rich in chain prenylated isoflavones (cIsf), one in chain prenylated stilbenoids (cSti), one in chain prenylated (cPta) and one in ring-closed prenylated pterocarpans (rPta), as characterized by RP-UHPLC-UV-MS. Antibacterial activity of the pools and membrane permeabilization was investigated. Pools showed high antibacterial activity against Listeria monocytogenes: cIsf pool had a minimum inhibitory concentration of 10µg/ml prenylated compounds, followed by cPta pool (25µg/ml) and cSti pool (35µg/ml). Activity against E. coli was found only when the pools were co-administered with an efflux pump inhibitor. The pool enriched in chain prenylated isoflavones permeabilized the bacterial membrane within minutes of exposure, whereas ampicillin did not. Bent conformation and chain prenylation, were molecular features of main prenylated phenolics found in pools with high antibacterial activity.

Laminaria digitata phlorotannins decrease protein degradation and methanogenesis during in vitro ruminal fermentation.

BACKGROUND: Phlorotannins (PhTs) are marine tannins consisting of phloroglucinol subunits connected via carbon-carbon and ether linkages. These have non-covalent protein binding properties and are, therefore, expected to be beneficial in protecting protein from hydrolysis during ruminal fermentation. In this study, the effectiveness of a methanolic PhTs extract from Laminaria digitata (10, 20, 40, 50, 75 and 100 g kg-1 tannin-free grass silage, with or without addition of polyethylene glycol (PEG), was investigated in vitro on protection of dietary protein and reduction of methane (CH4 ) in ruminal fluid. RESULTS: Addition of PhTs had linear (P < 0.0001) and quadratic (P = 0.0003) effects on gas and CH4 production, respectively. Optimal dosage of PhTs was 40 g kg-1 as at this point CH4 decreased (P < 0.0001) from 24.5 to 15.2 mL g-1 organic matter (OM), without affecting gas production (P = 0.3115) and total volatile fatty acids (P = 1.000). Ammonia trended (P = 0.0903) to decrease from 0.49 to 0.39 mmol g-1 OM, indicating protection of protein. Addition of PEG inhibited the effect of tannins at all dosage levels, and none of the fermentation parameters differed from the control. CONCLUSION: PhTs effectively protected protein from fermentation and reduced ruminal methanogenesis. © 2017 Society of Chemical Industry.

Quantification of the catalytic performance of C1-cellulose-specific lytic polysaccharide monooxygenases.

Lytic polysaccharide monooxygenases (LPMOs) have recently been shown to significantly enhance the degradation of recalcitrant polysaccharides and are of interest for the production of biochemicals and bioethanol from plant biomass. The copper-containing LPMOs utilize electrons, provided by reducing agents, to oxidatively cleave polysaccharides. Here, we report the development of a ß-glucosidase-assisted method to quantify the release of C1-oxidized gluco-oligosaccharides from cellulose by two C1-oxidizing LPMOs from Myceliophthora thermophila C1. Based on this quantification method, we demonstrate that the catalytic performance of both MtLPMOs is strongly dependent on pH and temperature. The obtained results indicate that the catalytic performance of LPMOs depends on the interaction of multiple factors, which are affected by both pH and temperature.

Resolubilization of Protein from Water-Insoluble Phlorotannin-Protein Complexes upon Acidification.

Marine phlorotannins (PhT) from Laminaria digitata might protect feed proteins from ruminal digestion by formation of insoluble non-covalent tannin-protein complexes at rumen pH (6-7). Formation and disintegration of PhT-protein complexes was studied with ß-casein (random coil) and bovine serum albumin (BSA, globular) at various pH. PhT had similar binding affinity for ß-casein and BSA as pentagalloyl glucose, as studied by fluorescence quenching. The affinity of PhT for both proteins was independent of pH (3.0, 6.0, and 8.0). In the presence of PhT, the pH range for precipitation of tannin-protein complexes widened to 0.5-1.5 pH units around the isoelectric point (pI) of the protein. Complete protein resolubilization from insoluble PhT-protein complexes was achieved at pH 7 and 2 for ß-casein and BSA, respectively. It was demonstrated that PhT modulate the solubility of proteins at neutral pH and that resolubilization of PhT-protein complexes at pH deviating from pI is mainly governed by the charge state of the protein.

Potential of a gypsum-free composting process of wheat straw for mushroom production.

Wheat straw based composting generates a selective substrate for mushroom production. The first phase of this process requires 5 days, and a reduction in time is wished. Here, we aim at understanding the effect of gypsum on the duration of the first phase and the mechanism behind it. Hereto, the regular process with gypsum addition and the same process without gypsum were studied during a 5-day period. The compost quality was evaluated based on compost lignin composition analysed by py-GC/MS and its degradability by a commercial (hemi-)cellulolytic enzyme cocktail. The composting phase lead to the decrease of the pyrolysis products 4-vinylphenol and 4-vinylguaiacol that can be associated with p-coumarates and ferulates linking xylan and lignin. In the regular compost, the enzymatic conversion reached 32 and 39% for cellulose, and 23 and 32% for xylan after 3 and 5 days, respectively. In absence of gypsum similar values were reached after 2 and 4 days, respectively. Thus, our data show that in absence of gypsum the desired compost quality was reached 20% earlier compared to the control process.

Quantification of Lignin and Its Structural Features in Plant Biomass Using 13C Lignin as Internal Standard for Pyrolysis-GC-SIM-MS.

Understanding the mechanisms underlying plant biomass recalcitrance at the molecular level can only be achieved by accurate analyses of both the content and structural features of the molecules involved. Current quantification of lignin is, however, majorly based on unspecific gravimetric analysis after sulfuric acid hydrolysis. Hence, our research aimed at specific lignin quantification with concurrent characterization of its structural features. Hereto, for the first time, a polymeric 13C lignin was used as internal standard (IS) for lignin quantification via analytical pyrolysis coupled to gas chromatography with mass-spectrometric detection in selected ion monitoring mode (py-GC-SIM-MS). In addition, relative response factors (RRFs) for the various pyrolysis products obtained were determined and applied. First, 12C and 13C lignin were isolated from nonlabeled and uniformly 13C labeled wheat straw, respectively, and characterized by heteronuclear single quantum coherence (HSQC), nuclear magnetic resonance (NMR), and py-GC/MS. The two lignin isolates were found to have identical structures. Second, 13C-IS based lignin quantification by py-GC-SIM-MS was validated in reconstituted biomass model systems with known contents of the 12C lignin analogue and was shown to be extremely accurate (>99.9%, R2 > 0.999) and precise (RSD < 1.5%). Third, 13C-IS based lignin quantification was applied to four common poaceous biomass sources (wheat straw, barley straw, corn stover, and sugar cane bagasse), and lignin contents were in good agreement with the total gravimetrically determined lignin contents. Our robust method proves to be a promising alternative for the high-throughput quantification of lignin in milled biomass samples directly and simultaneously provides a direct insight into the structural features of lignin.

Comparison of Protein Extracts from Various Unicellular Green Sources.

Photosynthetic unicellular organisms are considered as promising alternative protein sources. The aim of this study is to understand the extent to which these green sources differ with respect to their gross composition and how these differences affect the final protein isolate. Using mild isolation techniques, proteins were extracted and isolated from four different unicellular sources (Arthrospira (spirulina) maxima, Nannochloropsis gaditana, Tetraselmis impellucida, and Scenedesmus dimorphus). Despite differences in protein contents of the sources (27-62% w/w) and in protein extractability (17-74% w/w), final protein isolates were obtained that had similar protein contents (62-77% w/w) and protein yields (3-9% w/w). Protein solubility as a function of pH was different between the sources and in ionic strength dependency, especially at pH < 4.0. Overall, the characterization and extraction protocol used allows a relatively fast and well-described isolation of purified proteins from novel protein sources.