Effects of l‐lysine/l‐arginine on the emulsion stability,textural, rheological and microstructural characteristics of chicken sausages

The effects of l ‐lysine (Lys), l ‐arginine (Arg) and soya protein isolated (SPI) on the physicochemical properties of chicken sausages were investigated. The results showed that the addition of Lys/Arg significantly decreased total expressible fluid and expressible fat, but significantly increased hardness, springiness, cohesiveness and chewiness of chicken sausage. Moreover, Lys and Arg were more effective than SPI. Rheology indicated that Lys/Arg increased final storage modulus and final loss modulus. Also, scanning electron microscope and confocal laser scanning microscopy disclosed that Lys or Arg was conducive to the formation of regular and uniform oil droplet surrounded integrate membrane. Overall, Lys/Arg exhibited a potential in the preparation of emulsion‐type meat products.     

Fed‐batch l‐(+)‐lactic acid fermentation of brewer's spent grain hydrolysate

Brewer's spent grain (BSG) hydrolysates were used for l ‐(+)‐lactic acid (LA) fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate fed‐batch LA fermentation of BSG hydrolysate with the addition of glucose, glucose and yeast extract, and wort during LA fermentation and its effect on fermentation parameters such as LA concentration, its volumetric productivity and yield, and L. rhamnosus cell viability. The highest LA yield, volumetric productivity and concentration of 93.3%, 2.0 g/L/h, and 116.1 g/L, respectively, were achieved with glucose and yeast extract addition during fermentation. In fed‐batch fermentation with glucose and yeast extract addition significantly higher LA concentration, yield and volumetric productivity (by 194.8; 2.2, and 20.7%, respectively) were achieved compared with batch fermentation. The results indicated that fed‐batch fermentation could be used to increase LA fermentation efficiency. Copyright © 2017 The Institute of Brewing & Distilling     

3‐Hydroxypyridinone‐l‐phenylalanine conjugates with antimicrobial and tyrosinase inhibitory activities as potential shrimp preservatives

To explore the potential of novel tyrosinase inhibitors, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates, as shrimp preservatives, compounds 1 and 2 were evaluated for the antimicrobial activity, and compound 2 was investigated for the shrimp preservative efficacy. It was found that they both possess a stronger antibacterial effect than kojic acid against two Gram‐positive bacteria and three Gram‐negative bacteria. The minimum inhibitory concentrations (MICs) of compound 2 against Escherichia coli, Staphylococcous aureus, Salmonella gallinarum, Vibrio parahaemolyticus and Bacillus subtilis were determined as 18.5, 37, 148, 37 and 295 μg mL^?1, respectively, whereas MICs of kojic acid against the same 5 bacterial strains were determined to be 355, 178, 1420, 1420 and 355 μg mL^?1, respectively. It has also been demonstrated that treatment with compound 2 improves the sensory properties, retards the growth of spoilage bacteria, decreases the total volatile basic nitrogen (TVB‐N) and increases the pH of Penaeus vannamei Boone, thereby extending the shelf life to 10 days. In contrast, the shelf life of shrimp treated with kojic acid and the control group was 7 and 6 days, respectively. Clearly, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates could find application as shrimp preservatives by inhibiting melanosis and by preventing the growth of bacteria during the storage.     

α‐l‐Rhamnosidase from Aspergillus flavus MTCC‐9606 isolated from lemon fruit peel

An α‐l ‐rhamnosidase producing fungal strain has been isolated from decaying lemon fruit. The fungal strain has been identified as Aspergillus flavus. The α‐l ‐rhamnosidase has been purified from the culture filtrate of the fungal strain using ultra filtration and cation exchange chromatography on carboxy methyl (CM) cellulose. The molecular mass of the purified enzyme determined by SDS–PAGE analysis was 41 kDa. The K_m values of the enzyme using p‐nitrophenyl‐α‐l ‐rhamnopyranoside and naringin as the substrates were 1.89 and 1.6 mm respectively. The pH and temperature optima of the enzyme were 11.0 and 50 °C respectively. The effects of various chemical species present in grape fruit juice and wine on the activity of the enzyme have been determined.     

Different response to acetic acid stress in Saccharomyces cerevisiae wild‐type and l‐ascorbic acid‐producing strains

Biotechnological processes are of increasing significance for industrial production of fine and bulk chemicals, including biofuels. Unfortunately, under operative conditions microorganisms meet multiple stresses, such as non‐optimal pH, temperature, oxygenation and osmotic stress. Moreover, they have to face inhibitory compounds released during the pretreatment of lignocellulosic biomasses, which constitute the preferential substrate for second‐generation processes. Inhibitors include furan derivatives, phenolic compounds and weak organic acids, among which acetic acid is one of the most abundant and detrimental for cells. They impair cellular metabolism and growth, reducing the productivity of the process: therefore, the development of robust cell factories with improved production rates and resistance is of crucial importance. Here we show that a yeast strain engineered to endogenously produce vitamin C exhibits an increased tolerance compared to the parental strain when exposed to acetic acid at moderately toxic concentrations, measured as viability on plates. Starting from this evidence, we investigated more deeply: (a) the nature and levels of reactive oxygen species (ROS); (b) the activation of enzymes that act directly as detoxifiers of reactive oxygen species, such as superoxide dismutase (SOD) and catalase, in parental and engineered strains during acetic acid stress. The data indicate that the engineered strain can better recover from stress by limiting ROS accumulation, independently from SOD activation. The engineered yeast can be proposed as a model for further investigating direct and indirect mechanism(s) by which an antioxidant can rescue cells from organic acid damage; moreover, these studies will possibly provide additional targets for further strain improvements. Copyright © 2013 John Wiley & Sons, Ltd.     

Purification,characterisation and application of α‐l‐rhamnosidase from Penicillium citrinum MTCC‐8897

An α‐l ‐rhamnosidase secreted by Penicillium citrinum MTCC‐8897 has been purified to homogeneity from the culture filtrate of the fungal strain using ammonium sulphate precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The sodium dodecyl sulphate/polyacrylamide gel electrophoresis analysis of the purified enzyme gave a single protein band corresponding to the molecular mass 51.0 kDa. The native polyacrylamide gel electrophoresis also gave a single protein band confirming the enzyme purity. The K_m and V_max values of the enzyme for p‐nitrophenyl α‐l ‐rhamnopyranoside were 0.36 mm and 22.54 μmole min^?1 mg^?1, respectively, and k_cat value was 17.1 s^?1 giving k_cat/K_m value of 4.75 × 10⁴ m ^?1 s^?1. The pH and temperature optima of the enzyme were 7.0 and 60 °C, respectively. The purified enzyme liberated l ‐rhamnose from naringin, rutin, hesperidin and wine, indicating that it has biotechnological application potential for the preparation of l ‐rhamnose and other pharmaceutically important compounds from natural glycosides containing terminal α‐l ‐rhamnose and also in the enhancement of wine aroma.     

Purification and functional characterisation of an α‐l‐rhamnosidase from Penicillium citrinum MTCC‐3565

An extracellular α‐l ‐rhamnosidase from Penicillium citrinum MTCC‐3565 has purified to homogeneity from its culture filtrate using ethanol precipitation and cation‐exchange chromatography on carboxymethyl cellulose. The purified enzyme gave a single protein band corresponding to molecular mass of 45.0 kDa in SDS‐PAGE analysis showing the purity of the enzyme preparation. The native PAGE analysis showed the monomeric nature of the purified enzyme. Using p‐nitrophenyl α‐l ‐rhamnopyranoside as substrate, K_m and V_max values of the enzyme were 0.30 mm and 27.0 μm min mg^?1, respectively. The k_cat value was 20.1 s giving k_cat/K_m value of 67.0 mm s^?1 for the same substrate. The pH and temperature optima of the enzyme were 8.5 and 50 °C, respectively. The activation energy for the thermal denaturation of the enzyme was 29.9 KJ mol^?1. The α‐l ‐rhamnosidase was able to hydrolyse naringin, rutin and hesperidin and liberated l ‐rhamnose, indicating that the purified enzyme can be used for the preparation of α‐l ‐rhamnose and pharmaceutically important compounds by derhamnosylation of natural glycosides containing terminal α‐l ‐rhamnose. The α‐l ‐rhamnosidase was active at the level of ethanol concentration present in wine, indicating that it can be used for improving wine aroma.     

Role of Heavy Meromyosin in Heat‐Induced Gelation in Low Ionic Strength Solution Containing l‐Histidine

The gelation of myosin has a very important role in meat products. We have already shown that myosin in low ionic strength solution containing l ‐histidine forms a transparent gel after heating. To clarify the mechanism of this unique gelation, we investigated the changes in the nature of myosin subfragments during heating in solutions with low and high ionic strengths with and without l ‐histidine. The hydrophobicity of myosin and heavy meromyosin (HMM) in low ionic strength solution containing l ‐histidine was lower than in high ionic strength solution. The SH contents of myosin and HMM in low ionic strength solution containing l ‐histidine did not change during the heating process, whereas in high ionic strength solution they decreased slightly. The heat‐induced globular masses of HMM in low ionic strength solution containing l ‐histidine were smaller than those in high ionic strength solution. These findings suggested that the polymerization of HMM molecules by heating was suppressed in low ionic strength solution containing l ‐histidine, resulting in formation of the unique gel.     

Diverse Profiles of N‐acyl Homoserine l‐Lactones,Biofilm, Virulence Genes and Integrons in Food‐Borne Aeromonas Isolates

Aeromonas are regarded as opportunistic as well as primary pathogens of humans and fish, and are associated with gastroenteritis and septicemia in humans. Production of N‐acyl‐homoserine lactone (AHL) signal molecules and biofilm was determined in 22 Aeromonas isolates, from different food products in India, using thin‐layer chromatography (TLC) analysis and microtiter‐plate assay, respectively. Overall, highly heterogeneous patterns of AHL production were observed, with the production of N‐butanoyl homoserine lactone (C4‐HSL) and N‐hexanoyl homoserine lactone (C6‐HSL) by the majority (81.8%) of Aeromonas food isolates. Moreover, putative N‐pentanoyl homoserine lactone (C5‐HSL), N‐heptanoyl homoserine lactone (C7‐HSL), and N‐octanoyl homoserine lactone (C8‐HSL) were produced by 72.7%, 27.3%, and 9.1% of isolates, respectively. This is the 1st report of production of C7‐HSL by Aeromonas species. Aeromonas food isolates were highly variable in their biofilm forming abilities with majority of them as weak biofilm producers in 2 different media, TSB and M9 minimal medium supplemented with 0.4% glucose. The genes encoding for putative virulence factors, glycerophospholipid cholesterol acyltransferase (gcat), heat‐labile cytotonic enterotoxin (alt), heat‐stable cytotonic enterotoxin (ast), serine protease (ser), polar flagella (fla), and lateral flagella (lafA) were present in 95.5%, 59.1%, 22.7%, 81.8%, 77.3%, and 22.7% of the strains, respectively. Class 1 integrons (100 to 3000 bp) were found in 68.2% of food isolates; whereas, 50% isolates contained class 2 integrons (150 to 1600 bp). This study provides a baseline data on the diversity of AHLs, biofilm forming ability and presence of virulence genes and integrons in Aeromonas food isolates from India.     

An α‐l‐rhamnosidase from Aspergillus awamori MTCC‐2879 and its role in debittering of orange juice

The extracellular α‐l ‐rhamnosidase has been purified by growing a new fungal strain Aspergillus awamori MTCC‐2879 in the liquid culture growth medium containing orange peel. The purification procedure involved ultrafiltration using PM‐10 membrane and anion‐exchange chromatography on diethyl amino ethyl cellulose. The purified enzyme gave single protein band in SDS‐PAGE analysis corresponding to molecular mass 75.0 kDa. The native PAGE analysis of the purified enzyme also gave a single protein band, confirming the purity of the enzyme. The K_m and V_max values of the enzyme for p‐nitrophenyl‐α‐l ‐rhamnopyranoside were 0.62 mm and 27.06 μmole min^?1 mg^?1, respectively, yielding k_cat and k_cat/k_m values 39.90 s^?1 and 54.70 mm ^?1 s^?1, respectively. The enzyme had an optimum pH of 7.0 and optimum temperature of 60 °C. The activation energy for the thermal denaturation of the enzyme was 35.65 kJ^?1 mol^?1 K^?1. The purified enzyme can be used for specifically cleaving terminal α‐l ‐rhamnose from the natural glycosides, thereby contributing to the preparation of pharmaceutically important compounds like prunin and l ‐rhamnose.     

Lycopene‐derived bioactive retinoic acid receptors/retinoid‐X receptors‐activating metabolites may be relevant for lycopene's anti‐cancer potential

Dietary consumption of tomato products and especially the red tomato pigment lycopene has been associated with lower risk of cancer. New evidence is emerging toward metabolic pathways mediating the anti‐cancer activities of lycopene. In this review, we explore associations between tomatoes and lycopene intake and cancer and relate this to the metabolic activation pathways of lycopene via carotene oxygenases and further carotenoid/retinoid‐metabolizing enzymes to apo‐lycopenoids. Several of these apo‐lycopenoids have already been identified but up to date no direct connection between lycopene metabolism and apo‐lycopenoids mediated receptor activation pathways has been established. Retinoic acid receptors/retinoid‐X receptors activation pathways in particular, may be mediated via lycopene metabolites that are related to retinoic acids. Various studies have shown an association between lower concentration of insulin‐like growth factor‐1 upon lycopene treatment, cancer incidences, and retinoid‐mediated signaling. In this review, we interrelate tomato/lycopene ingestion and cancer incidence, with metabolic activation of lycopene and retinoid‐mediated signaling. The aim is to discuss a potential mechanism to explain lycopene related anti‐cancer activities by modulation of insulin‐like growth factor‐1 concentrations via lycopene metabolite activation of retinoid‐mediated signaling.