Antioxidant properties of bovine liver protein hydrolysates and their practical application in biphasic systems.

BACKGROUND: The influence of protein hydrolysate produced from bovine liver protein hydrolysate (LPH) by enzymatic hydrolysis, using Alcalase/Protamex (1:1), on lipid dispersions was investigated. LPH production was optimized to maximize the antioxidant activity (at 45, 50, and 55 °C for 12, 18, and 24 h). Different concentrations of LPHs (1, 3, and 5 mg/g) were added to emulsions and to liposomes. Lipid oxidation level and particle size of the lipid dispersions were monitored for 14 days of storage at 25 °C. RESULTS: Radical scavenging activity and reducing power were the highest at 45 °C after 24 h of hydrolysis. Electrophoresis pattern showed that the antioxidant activity was arising from the peptides with molecular weight around 10 kDa. Lipid oxidation occurred more rapidly in samples without LPH during storage. In emulsions, lower thiobarbituric acid-reactive substance and conjugated diene values were measured with increasing concentrations of LPH at day 14. Accordingly, particle size of the samples containing 5 mg/g of LPH was smaller than those of other groups. Phase separation was observed only in lecithin emulsion without LPH at day 14. The use of LPH in liposome limited the lipid oxidation and maintained the size of the particles independently from the concentration. CONCLUSION: This study highlights the potential applications of animal by-products as natural antioxidants in complex food systems. The results demonstrate that LPH, particularly when hydrolyzed at optimized conditions, can effectively inhibit lipid oxidation. The findings suggest that biphasic systems incorporating LPH have promising prospects for enhancing the stability and quality of food products. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of chitosan-essential oil, a surface mold inhibitor, on microbiological and physicochemical characteristics of semidried fermented sausages.

Mold growth on sausage casing during processing is an important problem in fermented sausages. In this work, sausages were dipped into 1% chitosan (C), 1% thyme essential oil in 1% chitosan (CT), 1% rosemary essential oil in 1% chitosan (CR), 20% potassium sorbate (PS) as chemical antifungal, and 1% acetic acid solution (AA) as chitosan solver, or distilled water (DW) as control after fermentation (at day 4). The changes in microbiological (total viable count, lactic acid bacteria [LAB], Micrococcaceae, Enterobacteriaceae, and mold and yeast counts) and physicochemical attributes of the sausages during 12 days of processing were monitored. As expected, LAB were the most dominant microbiota in fermented sausages and the dipping process did not have any negative effect. Additionally, the treatment with C, CT, and CR suppressed the growth of spoilage microorganisms, which resulted in a significant reduction (P < 0.01) of about 1.4 to 1.6 log CFU/g in Enterobacteriaceae counts at day 12. The C, CT, and CR similarly suppressed the growth of fungi in the interior of the sausages, and the antifungal treatment significantly reduced (P < 0.01) the load of fungi on the casing. Throughout the study, approximately log counts of 3 and 4 in lower molds and yeasts in the casings treated with PS and CR were found, respectively, as compared to DW. Finally, the microbial quality of the end product was notably improved. PRACTICAL APPLICATION: Processing conditions such as high humidity and O2 in the ripening chamber result in undesirable fungal growth on the casings of the sausages. Fermented sausages are usually treated with weak acids such as sorbic or benzoic acids or their salts to inhibit mold growth during the drying process. However, increasing consumer demand to reduce the use of chemicals encourages the applications of natural antifungals.

Effects of chitosan as a surface fungus inhibitor on microbiological, physicochemical, oxidative and sensory characteristics of dry fermented sausages.

The study aimed to improve the quality characteristics of Turkish dry-fermented sausages (sucuk) using different concentrations of chitosan (CH) coating as superficial mold inhibitor. The sausages were treated (w/w) with chitosan (0.2%, CH1; 0.5%, CH2 and 1%, CH3), potassium sorbate (20%, PS), acetic acid (1%, AA) and distilled water. Treatment with PS and CH3 resulted in a remarkable reduction of mold and yeast counts in the sausages and on casings at the end of ripening. Total aerobic mesophilic bacteria and lactic acid bacteria (LAB) varied from 7.19-7.29 to 9.01-9.27 and from 6.37-6.44 to 8.53-8.93 log CFU/g at day 0 and 12, respectively. Treatment with chitosan did not affect the natural microbiota of the sausages. Enterobacteriaceae counts were lowered from 5.79-5.89 to 2.08-2.53 log CFU/g by chitosan. Moreover, the rate of lipid oxidation in the sausages decreased by chitosan treatment. Sensory attributes were also notably enhanced in the cooked sausages treated with chitosan.

Workshops Without Walls: broadening access to science around the world.

The National Aeronautics and Space Administration (NASA) Astrobiology Institute (NAI) conducted two "Workshops Without Walls" during 2010 that enabled global scientific exchange--with no travel required. The second of these was on the topic "Molecular Paleontology and Resurrection: Rewinding the Tape of Life." Scientists from diverse disciplines and locations around the world were joined through an integrated suite of collaborative technologies to exchange information on the latest developments in this area of origin of life research. Through social media outlets and popular science blogs, participation in the workshop was broadened to include educators, science writers, and members of the general public. In total, over 560 people from 31 US states and 30 other nations were registered. Among the scientific disciplines represented were geochemistry, biochemistry, molecular biology and evolution, and microbial ecology. We present this workshop as a case study in how interdisciplinary collaborative research may be fostered, with substantial public engagement, without sustaining the deleterious environmental and economic impacts of travel.

Catalytic and inhibitor binding properties of zebrafish monoamine oxidase (zMAO): comparisons with human MAO A and MAO B.

A comparative investigation of substrate specificity and inhibitor binding properties of recombinant zebrafish (Danio rerio) monoamine oxidase (zMAO) with those of recombinant human monoamine oxidases A and B (hMAO A and hMAO B) is presented. zMAO oxidizes the neurotransmitter amines (serotonin, dopamine and tyramine) with k(cat) values that exceed those of hMAO A or of hMAO B. The enzyme is competitively inhibited by hMAO A selective reversible inhibitors with the exception of d-amphetamine where uncompetitive inhibition is exhibited. The enzyme is unreactive with most MAO B-specific reversible inhibitors with the exception of chlorostyrylcaffeine. zMAO catalyzes the oxidation of para-substituted benzylamine analogs exhibiting (D)k(cat) and (D)(k(cat)/K(m)) values ranging from 2 to 8. Structure-activity correlations show a dependence of log k(cat) with the electronic factor σ(p) with a ρ value of +1.55±0.34; a value close to that for hMAO A but not with MAO B. zMAO differs from hMAO A or hMAO B in benzylamine analog binding correlations where an electronic effect (ρ=+1.29±0.31) is observed. These data demonstrate zMAO exhibits functional properties similar to hMAO A as well as exhibits its own unique behavior. These results should be useful for studies of MAO function in zebrafish models of human disease states.

Expression of zebrafish (Danio rerio) monoamine oxidase (MAO) in Pichia pastoris: purification and comparison with human MAO A and MAO B.

The expression, purification and characterization of zebrafish monoamine oxidase (zMAO) using the methylotropic yeast Pichia pastoris expression system is described. A 1L fermentation culture of Pichia pastoris containing the gene encoding zMAO under control of the methanol oxidase promotor expresses approximately 200mg of zMAO exhibiting 300 U of total activity. The enzyme is found in the mitochondrial fraction of the expression host and is purified in a 30% yield as a homogenous species with a M(r) of approximately 60,000 on SDS-PAGE and a mass of 58,525+/-40 Da from MALDI-TOF measurements. The zMAO preparation contains one mole of covalent flavin cofactor per mole of enzyme and exhibits >80% functionality. The covalent flavin exhibits fluorescence and EPR spectral properties consistent with known properties of 8 alpha-S-cysteinyl FAD. Chemical degradation of the flavin peptide results in the liberation of FAD. zMAO exhibits no immuno-chemical cross-reactivity with polyclonal anti-sera raised against human MAO A. The enzyme preparation exhibits reasonable thermostability up to a temperature of 30 degrees C. Benzylamine is oxidized with a k(cat) value of 4.7+/-0.1 min(-1) (K(m)=82+/-9 microM) and the enzyme oxidizes phenylethylamine with a k(cat) value of 204 min(-1) (K(m)=86+/-13 microM). The K(m) (O(2)) values determined for zMAO using either benzylamine or phenylethylamine as substrates ranges from 108(+/-5) to 140(+/-21)microM. The functional behavior of this teleost MAO relative to human MAO A and MAO B is discussed.