In vitrostudies on the main beer protein Z4 ofHordeum vulgareconcerning heat stability, protease inhibition and gushing

Purification and Identification of Lipid-Lowering Protein from Barley Extract after Lactiplantibacillus plantarum dy-1 fermentation

Previous studies have found that the protein in barley extract fermented by Lactiplantibacillus plantarum dy-1 has the ability to inhibit lipid accumulation. However, the isolation, purification, and structural identification of the protein with lipid-lowering activity were still needed. In the present study, barley protein fermented by L. plantarum dy-1 with the optimal lipid-lowering ability was isolated and purified in three steps: using ammonium sulfate precipitation, anion-exchange chromatography, and size-exclusion chromatography. Combined with the model of HepG2 cells induced by oleic acid, the results showed that the pure protein LFBEP-C1 had the best lipid-lowering potential. Furthermore, our research found that LFBEP-C1 enriched the content of hydrophobic amino acids in LFBEP-C1. Ultraviolet spectroscopy analysis indicated that the glycosidic bond in LFBEP-C1 was an O-type glycosidic bond. The FTIR and circular dichroism spectra indicated that α-helix and random coil were the main secondary structures of LFBEP-C1. Mass spectrometry determined the theoretical molecular weight of LFBEP-C1 as 48 kDa, and its amino acid coverage was 63%. These findings suggest that the protein LFBEP-C1 with the best lipid-lowering activity was isolated and purified, and its structural characteristics were identified.

Genome Wide Identification and Comparative Analysis of the Serpin Gene Family in Brachypodium and Barley

Serpins (serine protease inhibitors) constitute one of the largest and most widely distributed superfamilies of protease inhibitors and have been identified in nearly all organisms. To gain significant insights, a comprehensive in silico analysis of the serpin gene family was carried out in the model plant for temperate grasses Brachypodium distachyon and barley Hordeum vulgare using bioinformatic tools at the genome level for the first time. We identified a total of 27 BdSRPs and 25 HvSRP genes in Brachypodium and barley, respectively, showing an unexpectedly high gene number in these model plants. Gene structure, conserved motifs and phylogenetic comparisons of serpin genes supported the role of duplication events in the expansion and evolution of serpin gene family. Further, purifying selection pressure was found to be a main driving force in the evolution of serpin genes. Genome synteny analysis indicated that BdSRP genes were present in syntenic regions of barley, rice, sorghum and maize, suggesting that they evolved before the divergence of these species from common ancestor. The distinct expression pattern in specific tissues further suggested a specialization of functions during development and in plant defense. These results suggest that the LR serpins (serpins with Leu-Arg residues at P2-P1') identified here can be utilized as candidates for exploitation in disease resistance, pest control and preventing stress-induced cell death. Additionally, serpins were identified that could lead to further research aimed at validating and functionally characterizing the role of potential serpin genes from other plants.

Sonicated extracts from the Quorn fermentation co-product as oil-lowering emulsifiers and foaming agents

Abstract

This study assessed the impact of sonication on the structure and properties of a functional extract (retentate 100 or R100) from the Quorn fermentation co-product (centrate). In a previous study, we reported that the R100 fraction displayed good foaming, emulsifying and rheological properties. Sonication of a R100 solution led to the breakdown of the large hyphal structures characteristic of this extract into smaller fragments. Foams prepared with sonicated R100 displayed a higher foaming ability than with untreated R100 and a high foam stability but lower than untreated R100 ones. Oil-in-water emulsions prepared with sonicated R100 displayed smaller oil droplet size distributions than with untreated R100. Confocal micrographs suggested that small fungal fragments contributed to the stabilisation of oil droplets. 50% oil-reduced R100 emulsions were prepared by mixing R100 emulsions (untreated or sonicated) with a sonicated R100 solution at a 1:1 ratio. Smaller oil droplet size distributions were reported for the oil-reduced emulsions. These results showed that the addition of small hyphal fragments or surface-active molecules and molecular aggregates released during sonication contributed to the formation and stabilisation of smaller oil droplets. This study highlighted the potential to modulate the structure, emulsifying and foaming properties of functional extracts from the Quorn fermentation co-product by sonication and the potential of these extracts as oil-lowering agents in emulsion-based products through the reduction of oil droplet size and their stabilisation.

Graphical abstract

Functional fungal extracts from the Quorn fermentation co-product as novel partial egg white replacers

Abstract

The production of mycoprotein biomass by Marlow Foods for use in their meat alternative brand Quorn is a potential source of sustainable alternatives to functional ingredients of animal origin for the food industry. The conversion of this viscoelastic biomass into the Quorn meat-like texture relies on functional synergy with egg white (EW), effectively forming a fibre gel composite. In a previous study, we reported that an extract (retentate 100 or R100) obtained from the Quorn fermentation co-product (centrate) via ultrafiltration displayed good foaming, emulsifying, and rheological properties. This current study investigated if a possible similar synergy between EW and R100 could be exploited to partially replace EW as foaming and/or gelling ingredient. The large hyphal structures characteristic of R100 solutions were observed in EW–R100 mixtures, while EW–R100 gels showed dense networks of entangled hyphal aggregates and filaments. R100 foams prepared by frothing proved less stable than EW ones; however, a 75/25 w/w EW–R100 mixture displayed a similar foam stability to EW. Simlarly, R100 hydrogels proved less viscoelastic than EW ones; however, the viscoelasticity of gels prepared with 50/50 w/w and 75/25 w/w EW–R100 proved similar to those of EW gels, while 75/25 w/w EW–R100 gels displayed similar hardness to EW ones. Both results highlighted a functional synergy between the R100 material and EW proteins. In parallel tensiometry measurements highlighted the presence of surface-active material in EW–R100 mixtures contributing to their high foaming properties. These results highlighted the potential of functional extracts from the Quorn fermentation process for partial EW replacement as foaming and gelling agent, and the complex nature of the functional profile of EW–R100 mixtures, with contributions reported for both hyphal structures and surface-active material.

Graphic abstract

Plant serpin protease inhibitors: specificity and duality of function

The serpins are a family of structurally conserved protease inhibitors found in all animal and plant kingdoms. After interaction with their cognate substrate(s), their native energetically stressed state is relaxed by hydrolysis, resulting in a semi-stable covalent bond that disables the protease. The inherent flexible serpin structure supports additional non-inhibitory functions. This review will focus on several biological functions attributed to plant serpins, ranging from specific cell death protease inhibitors to a stabilizing role for β-amylase in seeds. Functional conservation of a particular serpin type, the LR serpins, is suggested by its compelling ubiquity throughout the plant kingdom. The multiple target specificity of plant serpins including the LR serpins enables them to perform dual functions that are not mutually exclusive both as a regulator of cell death and as a protective anti-pathogenic protein.

Noncanonical interactions between serpin and β-amylase in barley grain improve β-amylase activity in vitro

Serpin protease inhibitors and β-amylase starch hydrolases are very abundant seed proteins in the endosperm of grasses. β-amylase is a crucial enzyme in the beer industry providing maltose for fermenting yeast. In animals and plants, inhibitory serpins form covalent linkages that inactivate their cognate proteases. Additionally, in animals, noninhibitory functions for serpins are observed such as metabolite carriers and chaperones. The function of serpins in seeds has yet to be unveiled. In developing endosperm, serpin Z4 and β-amylase showed similar in vivo spatio-temporal accumulation properties and colocalize in the cytosol of transformed tobacco leaves. A molecular interaction between recombinant proteins of serpin Z4 and β-amylase was revealed by surface plasmon resonance and microscale thermophoresis yielding a dissociation constant of 10-7 M. Importantly, the addition of serpin Z4 significantly changes β-amylase enzymatic properties by increasing its maximal catalytic velocity. The presence of serpin Z4 stabilizes β-amylase activity during heat treatment without affecting its critical denaturing temperature. Oxidative stress, simulated by the addition of CuCl2, leads to the formation of high molecular weight polymers of β-amylase similar to those detected in vivo. The polymers were cross-linked through disulfide bonds, the formation of which was repressed when serpin Z4 was present. The results suggest an unprecedented function for a plant seed serpin as a β-amylase-specific chaperone-like partner that could optimize β-amylase activity upon germination. This report is the first to describe a noninhibitory function for a serpin in plants.

Proteomic profiling of barley spent grains guides enzymatic solubilization of the remaining proteins

Within the brewing industry, malted barley is being increasingly replaced by raw barley supplemented with exogenous enzymes to lessen reliance on the time-consuming, high water and energy cost of malting. Regardless of the initial grain of choice, malted or raw, the resultant bulk spent grains are rich in proteins (up to 25% dry weight). Efficient enzymatic solubilization of these proteins requires knowledge of the protein composition within the spent grains. Therefore, a comprehensive proteomic profiling was performed on spent grains derived from (i) malted barley (spent grain A, SGA) and (ii) enzymatically treated raw barley (spent grain B, SGB); data are available via ProteomeXchange with identifier PXD008090. Results from complementary shotgun proteomics and 2D gel electrophoresis showed that the most abundant proteins in both spent grains were storage proteins (hordeins and embryo globulins); these were present at an average of two fold higher in spent grain B. Quantities of other major proteins were generally consistent in both spent grains A and B. Subsequent in silico protein sequence analysis of the predominant proteins facilitated knowledge-based protease selection to enhance spent grain solubilization. Among tested proteases, Alcalase 2.4 L digestion resulted in the highest remaining protein solubilization with 9.2 and 11.7% net dry weight loss in SGA and SGB respectively within 2 h. Thus, Alcalase alone can significantly reduce spent grain side stream, which makes it a possible solution to increase the value of this low-value side stream from the brewing and malt extract beverage manufacturing industry.