Protease Treatment Research Articles

Effect of enzyme‐assisted hydrolysis on brewer's spent grain protein solubilization – peptide composition and sensory properties

This study aimed to valorize brewer's spent grain (BSG) from a side-stream into protein ingredients suitable for human consumption. The impact of protease treatments was studied for solubilizing BSG proteins. Treatment with Protamex or simultaneous co-incubation of Protamex and Flavourzyme solubilized up to 60% of the total protein in BSG, whereas co-incubation with Flavourzyme increased the availability of hydrophobic amino acids (Val, Phe, Ala, Leu, Ile) in extracts. The scale-up of protease treatments demonstrated comparable solubilized protein fractions in 0.1 L and 10 L reaction volumes. Thorough sequence-based peptide analysis by liquid chromatography-ion mobility-mass spectrometry resulted in the identification of 479 and 451 water-soluble peptides in the hydrolysates obtained with Protamex or co-incubation of Protamex and Flavourzyme, respectively. Main cutting sites on BSG proteins were identified between Leu-Gln, Tyr-Phe, Pro-X (Protamex), complementing with a variety of cutting sites mainly next to Gln, Pro, Ile, and Phe when combined with Flavourzyme. Uniform protease activity throughout the entire B-hordein sequence and the formation of peptides with varying sequence lengths did not increase the bitterness of the hydrolysates compared to the BSG sample with water extraction. These results support the characterization of enzymatic treatments in plant-based materials and the production of hydrolysates with desired composition.

Newly Designed Decellularized Scaffolds for Scaffold-based Gene Therapy from Elastic Cartilages via Supercritical Carbon Dioxide Fluid and Alkaline/ Protease Treatments.

Scaffold-based gene therapy provides a promising approach for tissue engineering, which was important and popular as it combined medical applications and engineering materials' knowledge. The decellularization techniques were employed to remove the cellular components from porcine elastic cartilages, leaving a native decellularized Extracellular Matrix (dECM) composition and architecture integrity of largely insoluble collagen, elastin, and tightly bound glycosaminoglycans. For newly designed collagen scaffold samples, elastic cartilages were hydrolyzed by protease with different concentrations to gain state completely and clearly. An extraction process of Supercritical Carbon Dioxide (ScCO2) was used to remove cellular components from porcine elastic cartilage. The dECM scaffolds with collagen must be characterized by Fourier transform infrared spectroscopy(FTIR), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscope (SEM). The study provided a new treatment combined with supercritical carbon dioxide and alkaline/ protease to prepare dECM scaffolds with hole-scaffold microstructures and introduce into a potential application on osteochondral tissue engineering using scaffold-based gene therapy. The new process is simple and efficient. The pore-scaffold microstructures were observed in dECM scaffolds derived from porcine elastic cartilages. The Tdmax values of the resulting dECM scaffolds were observed at over 330oC. A series of new scaffolds were successfully obtained from porcine tissue by using ScCO2 and alkaline/enzyme treatments such as a mixing aqueous solution of NH4OH and papain. The dECM scaffolds with high thermal stability were obtained. The resulting scaffold with clean pore-scaffold microstructure could be a potential application for scaffold-based gene therapy.

Proteolytic enzyme-treated seaweed co-product (Ulva laetevirens) inclusion in corn-soybean and European broiler diets to improve digestibility, health, and performance

The impact of addition of an Ulva laetevirens (previously Ulva rigida) co-product treated with a broad-spectrum endo-protease when added to a standard corn-soy (S) based diet and a diet based on European protein sources (EU) on performance, in vivo digestibility and multiple gastrointestinal characteristics was investigated in broilers. In total, 624 Ross 308 one-day-old male broilers were fed one of 6 experimental diets (8 replicates) consisting of a basal diet (S or EU), or a basal diet including the U. laetevirens co-product (U) treated without (U-) or with (U+) a proteolytic enzyme. Starter diets contained 0 (wk 1) and 2.5 (wk 2), and the grower diets (wk 3 and 4) 5% seaweed co-product. In the last 2 wk, birds fed the S vs. EU grower diets showed a higher BW, BWG, and FI, as well as a lower FCR (−0.05 g/g) in wk 3 (P < 0.05). Heavier gizzards (+13%; P < 0.001) and heavier gizzard contents (+92%; P < 0.001) were observed in birds fed the EU vs. S diets, as well as longer villi (+8%; P = 0.010). U diets had a higher water holding capacity than the basal diets (+19%). In wk 4, U inclusion resulted in increased FCR (+0.06 g/g; P < 0.001), water intake (+7%; P < 0.001), and duodenal cross section (+5%; P = 0.033). Enzyme treatment did not affect digestibility of any nutrients, except for ash which was increased in birds fed U+ vs. U- diets (+60%; P < 0.001). U in S diets led to higher, and U in EU diets led to lower apparent pre-cecal digestibility of all nutrients (P < 0.001 for all nutrients). Although for both diet types performance was decreased, dietary U. laetevirens inclusion had different effects when added to a standard corn-soy diet and a diet based on European protein sources. No obvious health effects were observed, leading to the conclusion of the absence of performance of health promoting bioactive components in the U. laetevirens co-product, or of diminishing of these effects due to the proteolytic enzyme treatment.

The effects of different protease treatments on the techno-functional, structural, and bioactive properties of bovine casein

In this study, bovine sodium caseinate (NaCas) was hydrolyzed with four proteases, alcalase, savinase, subtilisin A, and flavourzyme. In addition to the structural changes occurred through the enzymatic hydrolysis, the solubility, oil binding capacity, zeta potential, emulsification properties, and in vitro antioxidant capacity, anti-carcinogenic and antidiabetic properties of hydrolysates were determined. FTIR combined with hierarchical cluster analysis (HCA) made in Amide I region enable to classification of the samples based on the changes of the secondary structure depending on the enzyme type and degree of fragmentation. Technological properties of NaCas were enhanced through the enzymatic hydrolysis, and those were more prominent in serine-type enzymes, regardless of the enzyme type, all hydrolysates showed high antioxidant capacities. All hydrolysates, specifically those produced by savinase and alcalase, reduced the viability of the carcinogenic Caco-2 cells in a dose-dependent manner and showed a very low level of cytotoxicity against healthy HEK-293 cells. The hydrolysis treatment made a significant contribution to the antidiabetic activity of NaCas. Particularly alcalase and savinase hydrolysates suppressed the activity of α- amylase and α- glucosidase. Therefore, the generated milk protein hydrolysates could be used in functional food developments for specific dietary purposes.

Antimicrobial Activity of Zymomonas mobilis Is Related to Its Aerobic Catabolism and Acid Resistance

Zymomonas mobilis is an ethanologenic, facultatively anaerobic alpha-proteobacterium, known for its inhibitory effect on the growth of a wide variety of microorganisms. This property might be interesting for the design of novel antimicrobials, yet it has negative implications for biotechnology, as it hinders the use of Z. mobilis as a producer microorganism in cocultivation. So far, the chemical nature of its inhibitory compound(s) has not been established. In the present study, we demonstrate that the putative inhibitor is a low-molecular-weight (below 3 kDa), thermostable compound, resistant to protease treatment, which is synthesized under aerobic conditions in Z. mobilis strains via the active respiratory chain. It is also synthesized by aerated nongrowing, glucose-consuming cells in the presence of chloramphenicol, thus ruling out its bacteriocin-like peptide nature. The inhibitory activity is pH-dependent and strongly correlated with the accumulation of propionate and acetate in the culture medium. Although, in Z. mobilis, the synthesis pathways of these acids still need to be identified, the acid production depends on respiration, and is much less pronounced in the non-respiring mutant strain, which shows low inhibitory activity. We conclude that propionate and acetate play a central role in the antimicrobial effects of Z. mobilis, which itself is known to bear high resistance to organic acids.

A proteolytic enzyme treatment to improve Ulva laetevirens and Solieria chordalis seaweed co-product digestibility, performance, and health in broilers

To explore the potential use of seaweed co-products for broiler diets, this study investigates whether an enzyme treatment of seaweed co-products improves performance, in vivo digestibility and health in broilers. In total, 360 Ross 308 male broilers were fed one of 5 experimental diets: a basal diet, or a basal diet including the U. laetevirens or S. chordalis co-product, with or without proteolytic enzyme treatment of the seaweed, using 6 replicate pens of 12 birds each. The starter (d 0–13) and grower (d 14–21) diet contained 5 and 10% (w/w) seaweed product, respectively. A general linear model with contrast statements was used after model assumptions and goodness of fit were evaluated through normal distribution of residuals. Inclusion of seaweed in the broiler diets increased body weight gain (+14%; P = 0.002), and feed intake (+12%; P = 0.001) in the third week of the experiment. Birds fed the U. laetevirens compared to the S. chordalis diets had a higher body weight gain (+11%; P = 0.007), and a lower feed conversion ratio (FCR; -7%; P < 0.001). Seaweed inclusion reduced apparent pre-cecal digestibility of all nutrients (P < 0.05). Birds fed U. laetevirens vs. S. chordalis diets had a 10% reduced villus length (P < 0.001). Enzymatic treatment reduced the digestibility of most nutrients, and increased crypt depth in birds fed the U. laetevirens diets, whereas the opposite was observed for the birds fed the S. chordalis diets (Seaweed × Enzyme P = 0.035). Untreated vs. treated seaweed in the diets led to lower (−60%) plasma Interleukin-13 levels (P = 0.035). In conclusion, the proteolytic enzyme treatment of the seaweed co-products did not improve performance nor health-related parameters, and reduced digestibility of the diets. Dietary inclusion of U. laetevirens co-products did improve performance based on growth and FCR, whereas inclusion of S. chordalis did not. Inclusion of U. laetevirens in broiler diets slightly reduced duodenal villus length and crypt depth. The inflammation response was strongly reduced, specifically in birds fed the untreated U. laetevirens diet, making the U. laetevirens co-product of interest for future research.

Transmitted light imaging reveals sarcomeric ultrastructure is preserved in expansion microscopy

Expansion Microscopy is a superresolution technique that employs a swellable hydrogel to physically expand a sample to approximately 4x its original size in each dimension. A labeled sample is crosslinked and embedded into acrylamide gel, then cleaved into fragments by a protease. As the gel absorbs water, it expands and pulls protein fragments apart from each other by an equal amount in all directions, enabling increased imaging resolution. Although the relative positions of fluorescent labels are maintained through the process, the optical properties of the proteins themselves were previously thought to be disrupted after protease treatment and expansion.

Optimization of fish oil extraction from Lophius litulon liver and fatty acid composition analysis

The Lophius litulon liver was used as raw material for the extraction of fish oil via various extraction methods. The extraction rate by water extraction, potassium hydroxide (KOH) hydrolysis and protease hydrolysis were compared and the results revealed the protease hydrolysis extraction had a higher extraction rate with good protein-lipid separation as observed by opticalmicroscope.Furthermore, subsequent experiments determined neutrase to be the best hydrolytic enzyme in terms of extraction rate and cost. The extraction conditions of neutrase hydrolysis were optimized by single-factor experiment and response surface analysis, and the optimal extraction rate was 58.40 ± 0.25% with the following conditions: enzyme concentration 2,000 IU/g, extraction time 1.0 h, liquid-solid ratio 1.95:1, extraction temperature 40.5°C and pH 6.5. The fatty acids composition in fish oil from optimized extraction condition was composed of 19.75% saturated fatty acids and 80.25% unsaturated fatty acids. The content of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were 8.06% and 1.19%, respectively, with the ratio (6.77:1) surpassed to the recommendation in current researches (5:1). The results in this study suggest protease treatment is an efficient method for high-quality fish oil extraction from Lophius litulon liver with a satisfactory ratio of DHA and EPA.

In Vitro and In Vivo Anti-Clostridioides difficile Effect of a Probiotic Bacillus amyloliquefaciens Strain.

Clostridioides difficile infection (CDI) is a significant cause of hospital-acquired and antibiotic-mediated intestinal diseases and is a growing global public health concern. Overuse of antibiotics and their effect on normal intestinal flora has increased the incidence and severity of infections. Thus, the development of new, effective, and safe treatment options is a high priority. Here, we report a new probiotic strain, Bacillus amyloliquefaciens (BA PMC-80), and its in vitro/in vivo anti-C. difficile effect as a prospective novel candidate for replacing conventional antibiotics. BA PMC-80 showed a significant anti-C. difficile effect in coculture assay, and its cell-free supernatant (CFS) also exhibited a considerable anti-C. difficile effect with an 89.06 μg/ml 50% minimal inhibitory concentration (MIC) in broth microdilution assay. The CFS was stable and equally functional under different pHs, heat, and proteinase treatments. It also exhibited a high sensitivity against current antibiotics and no toxicity in subchronic toxicity testing in hamsters. Finally, BA PMC-80 showed a moderate effect in a hamster CDI model with reduced infection severity and delayed death. However, further studies are required to optimize the treatment condition of the hamster CDI model for better efficacy and identify the antimicrobial compound produced by BA PMC-80.

Antifungal Activity of Lactobacillus plantarum ZZUA493 and Its Application to Extend the Shelf Life of Chinese Steamed Buns.

Lactic acid bacteria (LAB) can produce many kinds of antifungal substances, which have been widely proven to have antifungal activity. In this study, 359 strains of LAB were screened for antifungal activity against Aspergillus niger (A. niger) using the 96-well microtiter plate method, and three showed strong activity. Of these, ZZUA493 showed a broad-spectrum antifungal ability against A. niger, Aspergillus oryzae, Trichoderma longibrachiatum, Aspergillus flavus and Fusarium graminearum. ZZUA493 was identified as Lactobacillus plantarum. Protease treatment, the removal of hydrogen peroxide with catalase and heat treatment had no effect on the antifungal activity of the cell-free supernatant (CFS) of ZZUA493; organic acids produced by ZZUA493 appeared to have an important role in fungal growth inhibition. The contents of lactic acid, acetic acid and phenyllactic acid in the CFS tended to be stable at 48 h, and amounted to 28.5, 15.5 and 0.075 mg/mL, respectively. In addition, adding ZZUA493, as an ingredient during their preparation, prolonged the shelf life of Chinese steamed buns. Overall, ZZUA493 appears to have good potential as a fungal inhibitor for food preservation.

Inflammation at Site of Insulin Infusion Diminishes Glycemic Control

The approximation of euglycemia is the most effective means of preventing diabetic complications, which is achieved through effective insulin delivery. Recent reports indicate that insulin phenolic preservatives, which are found in all commercial insulin formulations, are cytotoxic, pro-inflammatory and induce secondary fibrosis. Therefore, we hypothesize that these preservatives induce an inflammatory response at the site of insulin infusion leading to diminished glycemic control and adverse pharmacokinetic outcomes. Insulin degradation by inflammatory cell proteases was quantitated following protease treatment in vitro. A modified murine air pouch model was utilized to evaluate the relative inflammatory responses following infusions of saline, insulin preservatives, and insulin, utilizing the adjuvant irritant thioglycolate. Blood glucose levels were monitored in diabetic mice with and without air pouch irritation. A pharmacokinetic analysis evaluated insulin effectiveness for diabetic mice between these two conditions.Inflammatory cells are significantly present in insulin preservative-induced inflammation, which effects diminished blood glucose control by both insulin uptake and degradation. Insulin containing these preservatives resulted in similar degrees of inflammation as observed with the irritant thioglycolate. These studies imply that the preservative agents found in commercial insulin formulations induce an intense localized inflammatory reaction. This inflammatory reaction may be responsible for the premature failure of insulin infusion devices. Future studies directed at reducing this inflammatory reaction may prove to be an important step in extending the lifespan of insulin infusion devices.

Genome-assisted Identification, Purification, and Characterization of Bacteriocins.

Bacteriocins are antimicrobial peptides with activity against antibiotic resistant bacterial pathogens. Here, we describe a set of methods aimed at purifying, identifying, and characterizing new bacteriocins. The purification consists of ammonium sulphate precipitation, cation-exchange chromatography, and reversed-phase chromatography. The yield of the bacteriocin is quantified by bacteriocin antimicrobial activity in a microtiter plate assay after each purification step. The mass of the purified bacteriocin is assessed by MALDI TOF MS analysis of the active fractions after reversed-phase chromatography. The mass is compared with the theoretical mass based on genetic information from the whole genome sequencing of the bacteriocin producer strain. Physicochemical characterization is performed by assessing antimicrobial activity following heat and protease treatments. Fluorescent techniques are used to examine the capacity of the bacteriocin to disrupt membrane integrity. Herein a set of protocols for purification and characterization of the bacteriocin nisin Z is used as a typical example in this paper.

A combined treatment of Proteinase K and biosynthesized ZnO-NPs for eradication of dairy biofilm of sporeformers.

Biofilms of sporeformers found in the dairy industry are the major contaminants during processing, as they withstand heat and chemical treatment that are used to control microbes. The present work is aimed to remove these resistant forms of bacterial community (biofilm) present in dairy production lines using ecofriendly agents based on proteinase K (Prot-K) coupled with Zinc oxide nanoparticles (ZnO-NPs). Some metal/metal oxide (Ag, CuO and ZnO) NPs were prepared microbially, and ZnO-NPs were characterized as the most effective ones among them. The produced ZnO-NPs were 15-25 nm in size with spherical shape, and FTIR analysis confirmed the presence of proteins and alkanes surrounding particles as capping agents. Application of Prot-K for eradication (removal) of a model biofilm of mixed sporeformers on food-grade stainless steel resulted in an 83% reduction in the absorbance of crystal violet-stained biofilm. When Prot-K was mixed with the biosynthesized NPs ZnO_G240, the reduction increased to 99.19%. This finding could contribute to an efficient cleaning approach combined with CIP to remove the recalcitrant biofilms in dairy production lines.

Expression and localization of tight junction-related proteins in adult rat pituitary stem/progenitor cell niches.

Pituitary endocrine cells are supplied by Sox2-expressing stem/progenitor cells in the anterior lobe of the adult pituitary gland. These SOX2-positive cells are maintained in two types of microenvironments (niches): the marginal cell layer (MCL)-niche and the parenchymal-niche. Recently, we isolated dense SOX2-positive cell clusters from the parenchymal-niche by taking advantage of their resistance to protease treatment as parenchymal stem/progenitor cell (PS)-clusters. In the present study, by analyzing these isolated PS-clusters, we attempted to identify novel structural characteristics of pituitary stem/progenitor cell niches. Quantitative real-time PCR showed that tight junction-related genes were distinctly expressed in the isolated PS-clusters. Immunocytostaining showed that the tight junction molecules, ZO-1 and occludin, were localized in the apical membrane facing the pseudo-follicle-like structure of the isolated PS-clusters regardless of the expression of S100β, which distinguishes the sub-population of SOX2-positive cells. Furthermore, immunohistochemistry of the pituitary glands of adult rats clearly demonstrated that ZO-1 and occludin were densely present in the parenchymal-niche encircling the pseudo-follicle, while they were observed in the apical membrane in the MCL-niche facing the residual lumen. Collectively, these tight junction-related proteins might be involved in the architecture and maintenance of the plasticity of pituitary stem/progenitor cell niches.

Effect of Compound Protease Treatment on the Quality Characteristics of Wheat Germ Powder

Effect of Compound Protease Treatment on the Quality Characteristics of Wheat Germ Powder

The roles of brewers’ spent grain derivatives in coconut-based yogurt-alternatives: Microstructural characteristic and the evaluation of physico-chemical properties during the storage

Water soluble coconut extract (WSCE) was reported as a suitable matrix for probiotic delivery as yogurt alternatives. The study aimed to evaluate the roles of brewers’ spent grain (BSG) derivatives in enhancing the properties of WSCE-based yogurt alternatives. BSG flour (BSGF) and 3 different protein extracts (BSGPs) including protein control (BSGP-C), protamex treatment (BSGP-P), and protamex combined with flavourzyme treatment (BSGP-PF) were incorporated in WSCE-based yogurt alternatives. Confocal laser scanning microscopy showed that BSGPs prepared with protease treatment generated less dense fat distribution and more homogenous globules compared to that in WSCE control yogurt. It also resulted in a softer, denser and more homogenous matrix. The modification in microstructural properties was aligned with differences in several functional groups including ⍺-glycosidic bond and hydroxyl groups from polysaccharides, aliphatic ethers and acid functional groups as well as aromatic hydrocarbons of lignin, amide I, acetyl groups and amide III. BSGF and BSGPs increased the mechanical properties, viscosity and modified flow behaviour properties demonstrating its ability in maintaining textural and gel formation. After 14 days of storage, maintenance in flow behaviour, syneresis and mechanical properties was identified. Furthermore, BSG derivatives enhanced lactic acid production up to 3 folds. In conclusion, BSG derivatives maintained the microstructure and gel formation, improved the properties of WSCE-based yogurt alternatives and preserved its behaviour during 14 days of storage.

The role of endogenous serine proteinase on disintegration of collagen fibers from grass carp (Ctenopharyngodon idellus)

Softening, causing by the degradation of collagen, leads to serious quality deterioration of fish fillets during post-mortem storage. In order to study the role of endogenous enzymes in softening of fish muscle, collagen fibers from grass carp (Ctenopharyngodon idellus) were degraded by serine proteinase. The structural and biochemical changes of collagen fibers with serine proteinase digestion were investigated in terms of scanning electron microscopy, fourier transform infrared spectroscopy, electrophoresis and chemical analysis. In the present study, an endogenous proteinase (approximately 250 kDa) with gelatinolytic activity was isolated from grass carp muscle by ammonium sulfate precipitation and column chromatographies, and identified as serine proteinase. Collagen fibers were partly disaggregated into collagen fibrils after serine proteinase treatment for 48 h, coinciding with a release of hydroxyproline (5.56 ± 0.02%) and glycosaminoglycans (9.04 ± 0.03%). However, almost all gelatin and 40% of acid-soluble collagen were degraded within 1 h and 6 h, respectively. Meanwhile, serine proteinase-treated collagen fibers maintained the triple-helical structure of collagen molecule, while their thermal stability was gradually decreased with digestion time. All results indicated that disintegration of collage fibers by serine proteinase might be due to both the degradation of proteoglycans and collagen molecules during textural deterioration of chilled grass carp fillets.

Lysine β-Hydroxybutyrylation Improves Stability of COVID-19 Antibody.

β-Hydroxybutyrate (3HB) is a small molecule produced as a ketone body in mammalian animals. It has been found that 3HB provides not only energy for a body, it also participates in cell signal transduction events as a signal molecule. This study focuses on investigation of 3HB immunomodulatory mechanisms. Proteomic analysis indicates a new post-translational modification of β-hydroxybutyrylation (Kbhb) on antibodies. Because of the low level of Kbhb antibodies and the associated difficulty in purifying them, simulated Kbhb antibody was produced using chemical modification in vitro. The chemically modified Kbhb antibody was shown to improve the stability of antibodies to protease and heat treatments. Furthermore, Kbhb of antibodies stabilizes the antibodies in plasma. As a remarkable example, COVID-19 neutralizing antibody B38 produced by 293T cells was Kbhb modified and stabilized in vivo, providing a strategy for the possibility of extending the protection effects of COVID-19 antibodies.

Black soldier fly larval meal with exogenous protease in diets for rainbow trout (Oncorhynchus mykiss) production meeting consumer quality

A protein gap exists within the supply of fish feed ingredients due to intensifying global aquaculture production and demands. This is distinctly acute in salmonid farming where protein requirements are higher to other aquatic farmed species. In pursuit of a viable alternative, an eight-week feeding trial was conducted to evaluate the feasibility of including reared black soldier fly (BSF, Hermetia illucens ) larvae into rainbow trout ( Oncorhynchus mykiss ) diets. Five diets were formulated: a fish meal-based basal diet (CTRL), two diets of BSF incorporation at 15 and 30% (BSF15; BSF30), and two diets at the same incorporation level with the addition of a supplementary protease enzyme (BSF15P; BSF30P) assigned to test potential dietary enhancement. No significant growth performance between the dietary treatments was observed. The fish condition factor in BSF30 was higher than BSF30P ( P =0.025). Fillets showed increased muscle yellowness as dietary BSF increased ( P =0.004). Trout fed BSF displayed significantly lower lipid peroxidation post-harvest ( P < 0.001), with the level of malondialdehyde decreasing with increased dietary BSF, regardless of protease inclusion. BSF meal elevated the saturated fatty acid content of fillets significantly ( P < 0.001) while monounsaturated fatty acids decreased ( P < 0.001). BSF protease treatments elevated the total concentration of protein in the trout body content, reflecting potentially improved protein utilisation efficiency. BSF diet with protease inclusion is a feasible protein and energy concentrate to replace fish meal in rainbow trout diets up to 30%, without negative effects on the growth, proximate composition, fatty acid profile, lipid peroxidation and fillet colour stability of rainbow trout. • Inclusion of black solider fly larvae meal maintains trout growth performance. • Increase in fillet lauric fatty acid content was found in insect meal fed trout. • Use of protease elevated protein content in trout fed with black solider fly meal. • Black soldier fly meal decreased fillet lipid peroxidation. • An increase of fillet yellowness was found in solider fly meal fed trout.

Effect of bacteriocin-producing Pediococcus acidilactici strains on the immune system and intestinal flora of normal mice

This study was performed to determine the effects of bacteriocin-producing and non-bacteriocin-producing Pediococcusacidilactici strains on the immune system and intestinal flora of normal mice. Two P. acidilactici strains with antibacterial activity (P. acidilactici CCFM28 and CCFM18) were obtained based on the inhibition-zone assay. The produced components were identified as bacteriocins through protease treatment, pH adjustment and hydrogen peroxide treatment. Bacteriocin-producing and non-bacteriocin-producing P. acidilactici strains (P. acidilactici CCFM28, CCFM18 and NT17-3) caused significant changes in serum immune factors and intestinal flora of normal mice. After 14 days of intervention, the relative abundance of Firmicutes was significantly decreased, but that of Proteobacteria was significantly increased at the phylum level. At the genus level, the administration of three P. acidilactici strains resulted in the downregulation of Blautia and the upregulation of Ruminococcus and Lactobacillus. Furthermore, there were also different regulations on some probiotic strains, such as Bifidobacterium, Coprococcus and Akkermansia, which were closely related to the antibacterial ability of the bacteriocin and the type of strain. The results indicated that the intervention of different P. acidilactici strains could differently change the structure of intestinal flora in normal mice, which provided theoretical guidance for the selective use of bacteriocin-producing strains for health regulation in the future.