scholarly journals Endolysins from Antarctic Pseudomonas Display Lysozyme Activity at Low Temperature

Marine Drugs ◽  
2020 ◽  
Vol 18 (11) ◽  
pp. 579
Author(s):  
Marco Orlando ◽  
Sandra Pucciarelli ◽  
Marina Lotti
Keyword(s):  
Low Temperature ◽  
Thermal Inactivation ◽  
Residual Activity ◽  
Heat Stability ◽  
Evolutionary Analysis ◽  
Glycosyl Hydrolases ◽  
Bioinformatics Analyses ◽  
Cold Environments ◽  
Local Flexibility ◽  
Cold Activity

Organisms specialized to thrive in cold environments (so-called psychrophiles) produce enzymes with the remarkable ability to catalyze chemical reactions at low temperature. Cold activity relies on adaptive changes in the proteins’ sequence and structural organization that result in high conformational flexibility. As a consequence of flexibility, several such enzymes are inherently heat sensitive. Cold-active enzymes are of interest for application in a number of bioprocesses, where cold activity coupled with easy thermal inactivation can be of advantage. We describe the biochemical and functional properties of two glycosyl hydrolases (named LYS177 and LYS188) of family 19 (GH19), identified in the genome of an Antarctic marine Pseudomonas. Molecular evolutionary analysis placed them in a group of characterized GH19 endolysins active on lysozyme substrates, such as peptidoglycan. Enzyme activity peaks at about 25–35 °C and 40% residual activity is retained at 5 °C. LYS177 and LYS188 are thermolabile, with Tm of 52 and 45 °C and half-lives of 48 and 12 h at 37 °C, respectively. Bioinformatics analyses suggest that low heat stability may be associated to temperature-driven increases in local flexibility occurring mainly in a specific region of the polypeptide that is predicted to contain hot spots for aggregation.

scholarly journals The Candidate Genes Underlying a Stably Expressed QTL for Low Temperature Germinability in Rice (Oryza sativa L.)

Rice ◽  
2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Tifeng Yang ◽  
Lian Zhou ◽  
Junliang Zhao ◽  
Jingfang Dong ◽  
Qing Liu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Differential Expression ◽  
Candidate Genes ◽  
Complex Traits ◽  
Molecular Breeding ◽  
Genome Wide Association Study ◽  
Oryza Sativa L ◽  
Sequence Comparisons ◽  
Cold Environments ◽  
Promising Source

Abstract Background Direct seeding is an efficient cultivation technique in rice. However, poor low temperature germinability (LTG) of modern rice cultivars limits its application. Identifying the genes associated with LTG and performing molecular breeding is the fundamental way to address this issue. However, few LTG QTLs have been fine mapped and cloned so far. Results In the present study, the LTG evaluation of 375 rice accessions selected from the Rice Diversity Panel 2 showed that there were large LTG variations within the population, and the LTG of Indica group was significantly higher than that of Japonica and Aus groups (p < 0.01). In total, eleven QTLs for LTG were identified through genome-wide association study (GWAS). Among them, qLTG_sRDP2–3/qLTG_JAP-3, qLTG_AUS-3 and qLTG_sRDP2–12 are first reported in the present study. The QTL on chromosome 10, qLTG_sRDP2–10a had the largest contribution to LTG variations in 375 rice accessions, and was further validated using single segment substitution line (SSSL). The presence of qLTG_sRDP2–10a could result in 59.8% increase in LTG under 15 °C low temperature. The expression analysis of the genes within qLTG_sRDP2–10a region indicated that LOC_Os10g22520 and LOC_Os10g22484 exhibited differential expression between the high and low LTG lines. Further sequence comparisons revealed that there were insertion and deletion sequence differences in the promoter and intron region of LOC_Os10g22520, and an about 6 kb variation at the 3′ end of LOC_Os10g22484 between the high and low LTG lines, suggesting that the sequence variations of the two genes could be the cause for their differential expression in high and low LTG lines. Conclusion Among the 11 QTLs identified in this study, qLTG_sRDP2–10a could also be detected in other three studies using different germplasm under different cold environments. Its large effect and stable expression make qLTG_sRDP2–10a particularly valuable in rice breeding. The two genes, LOC_Os10g22484 and LOC_Os10g22520, were considered as the candidate genes underlying qLTG_sRDP2–10a. Our results suggest that integrating GWAS and SSSL can facilitate identification of QTL for complex traits in rice. The identification of qLTG_sRDP2–10a and its candidate genes provide a promising source for gene cloning of LTG and molecular breeding for LTG in rice.

scholarly journals Optimization of β-1,4-Endoxylanase Production by an Aspergillus niger Strain Growing on Wheat Straw and Application in Xylooligosaccharides Production

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2527
Author(s):  
Zahra Azzouz ◽  
Azzeddine Bettache ◽  
Nawel Boucherba ◽  
Alicia Prieto ◽  
Maria Jesus Martinez ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Wheat Straw ◽  
Plant Biomass ◽  
Residual Activity ◽  
Exchange Chromatography ◽  
Glycosyl Hydrolases ◽  
Biomass Degradation ◽  
Xylan Hydrolysis ◽  
Rsm Optimization ◽  
Single Carbon Source

Plant biomass constitutes the main source of renewable carbon on the planet. Its valorization has traditionally been focused on the use of cellulose, although hemicellulose is the second most abundant group of polysaccharides on Earth. The main enzymes involved in plant biomass degradation are glycosyl hydrolases, and filamentous fungi are good producers of these enzymes. In this study, a new strain of Aspergillus niger was used for hemicellulase production under solid-state fermentation using wheat straw as single-carbon source. Physicochemical parameters for the production of an endoxylanase were optimized by using a One-Factor-at-a-Time (OFAT) approach and response surface methodology (RSM). Maximum xylanase yield after RSM optimization was increased 3-fold, and 1.41- fold purification was achieved after ultrafiltration and ion-exchange chromatography, with about 6.2% yield. The highest activity of the purified xylanase was observed at 50 °C and pH 6. The enzyme displayed high thermal and pH stability, with more than 90% residual activity between pH 3.0–9.0 and between 30–40 °C, after 24 h of incubation, with half-lives of 30 min at 50 and 60 °C. The enzyme was mostly active against wheat arabinoxylan, and its kinetic parameters were analyzed (Km = 26.06 mg·mL−1 and Vmax = 5.647 U·mg−1). Wheat straw xylan hydrolysis with the purified β-1,4 endoxylanase showed that it was able to release xylooligosaccharides, making it suitable for different applications in food technology.

scholarly journals Kinetic and Thermodynamic Analysis of Two Carboxymethylcellulases from Macrotermes subhyalinus Little Soldier

2017 ◽  
Vol 9 (4) ◽  
pp. 17
Author(s):  
Jean B. Fagbohoun ◽  
Mankambou J. Gnanwa ◽  
Fankroma M. T. Kone ◽  
S. Dabonne ◽  
Patrice L. Kouame
Keyword(s):  
Thermodynamic Parameters ◽  
Thermal Inactivation ◽  
Molecular Conformation ◽  
Residual Activity ◽  
Degradation Kinetic ◽  
Macrotermes Subhyalinus ◽  
Kinetic And Thermodynamic Parameters ◽  
Technology Applications ◽  
Kinetic And Thermodynamic Analysis ◽  
Increasing Temperature

Optimization of thermal processes relies on adequate degradation kinetic models to warrant food safety and quality. The knowledge on thermal inactivation of enzymes is necessary to allow their proper utilization in food industry and technology applications, enabling the reduction of heating times and optimization of heating temperatures. In this work, the kinetic of thermal inactivation was studied for the previously characterized carboxylmethylcellulases Ab-CX1 and Ab-CX2 from Macrotermes subhyalinus little soldier. Samples of carboxymethylcellulases were treated at different time-temperature combinations in the range of 5-60 min at 50-65°C and the kinetic and thermodynamic parameters for carboxymethylcellulases were calculated. Results showed that inactivation followed a first-order reaction with k-values between 0.0103 ± 0.0003 to 0.1217 ± 0.0005 and 0.0149 ± 0.0007 to 0.0416 ± 0.0003 min-1 for Ab-CX1 and Ab-CX2, respectively. At high temperatures, Ab-CX2 was less resistant, with a significant decrease in residual activity compared to Ab-CX1. The D- and k-values decreased and increased, respectively, with increasing temperature, indicating faster inactivation of carboxymethylcellulases. Activation energy (Ea) and Z-values were estimated to 76.74 ± 1.98 kJ.mol-1 and 24.21 ± 1.92 °C for Ab-CX1, 62.80 ± 2.05 kJ.mol-1 and 33.33 ± 2.78 °C for Ab-CX2. Thermodynamic parameters (ΔH#, ΔS# and ΔG#) were also calculated. The high value obtained for the variation in enthalpy of activation indicates that a high amount of energy is required to initiate denaturation, probably due to the molecular conformation of carboxymethylcellulases. All results suggest that both carboxymethylcellulases are relatively resistant to long heat treatments up to 50°C.

scholarly journals Peroxidase from peach fruit: thermal Stability

1998 ◽  
Vol 41 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Valdir Augusto Neves ◽  
E. J. Lourenço
Keyword(s):  
Sucrose Concentration ◽  
Residual Activity ◽  
Deae Cellulose ◽  
Heat Stability ◽  
Initial Activity ◽  
Fast Inactivation ◽  
Peach Fruit ◽  
Optimum Ph ◽  
Calculated Activation Energy ◽  
Calculated Activation

Peroxidase from peach fruit was purified 28.9-fold by DEAE-cellulose, Sephadex G-100 and hydroxylapatite chromatography. The purified enzyme showed only one peak of activity with an optimum pH of 5.0 and temperature of 40ºC. The calculated activation energy (Ea) for the reaction was 7.97 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 80ºC with a fast inactivation at 80ºC. PAGE of the inactivation course at 70ºC showed only one band of activity. Different sugars increased the heat stability of the activity in the following order: sucrose>lactose>glucose>fructose. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (10 to 40%, w/w) with the Ea for inactivation increasing with sucrose concentration from 0 to 20% (w/w). After inactivation at 70ºC and 75ºC the enzyme was able to be reactivated by up to 40% of the initial activity when stored at 30ºC.

The cooler side of mycorrhizas: their occurrence and functioning at low temperatures

2007 ◽  
Vol 85 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Mark Tibbett ◽  
John W.G. Cairney
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Mycorrhizal Fungi ◽  
Nutrient Acquisition ◽  
Significant Part ◽  
Freezing Resistance ◽  
Ecological Consequences ◽  
Cold Environments ◽  
Edaphic Conditions ◽  
Mycorrhizal Associations

Mycorrhizal associations occur in a range of habitats in which soils are subject to low temperature (≤15 °C) for a significant part of the year. Despite this, most of our understanding of mycorrhizal fungi and their interactions with their plant hosts is based on physiological investigations conducted in the range 20–37 °C using fungi of temperate origin. Comparatively little consideration has been given to the cold edaphic conditions in which many mycorrhizas survive and prosper, and the physiological and ecological consequences of their low temperature environments. In this review, we consider the distribution and persistence of arbuscular and ectomycorrhizal mycorrhizal associations in cold environments and highlight progress in understanding adaptations to freezing resistance and nutrient acquisition at low temperature in mycorrhizal fungi.

scholarly journals Synthesis of Low Temperature Resistant Hydrogenated Nitrile Rubber Based on Esterification Reaction

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4096
Author(s):  
Lin Wang ◽  
Yanqiang Ni ◽  
Xin Qi ◽  
Liqun Zhang ◽  
Dongmei Yue
Keyword(s):  
Low Temperature ◽  
Nitrile Rubber ◽  
Petroleum Exploration ◽  
Esterification Reaction ◽  
Grafted Polymers ◽  
Scanning Calorimetry ◽  
Temperature Resistance ◽  
Molecular Weights ◽  
Cold Environments ◽  
Low Temperature Resistance

Hydrogenated Nitrile Rubber (HNBR) is widely used in aerospace, petroleum exploration and other fields because of its excellent performances. However, there remains a challenge of balancing the oil resistance and the low temperature resistance for HNBR. In this work, a series of grafted carboxyl nitrile rubber (XNBR) was prepared by the esterification reaction between active functional groups (–COOH) of XNBR and alkanols of different molecular chain lengths (C8H17OH, C12H25OH, C16H33OH, C18H37OH) or Methoxypolyethylene glycols (MPEG) of different molecular weights (Mn = 350, 750, 1000). The structure and low temperature resistance of as-obtained grafted polymers were characterized by Fourier Transform Infrared (FTIR), 1H-NMR and Differential scanning calorimetry (DSC). It was found that the glass transition temperatures (Tg) of grafted XNBR were significantly decreased. MPEG grafted polymers with better low temperature resistance were then selected for hydrogenation. As-prepared hydrogenated XNBR grafted with MPEG-1000 (HXNBR-g-1000) showed the lowest Tg of −29.8 °C and the best low temperature resistance. This work provides a novel and simple preparation method for low temperature resistant HNBR, which might be used potentially in extremely cold environments.

Specific effects on strength and heat stability of intramuscular connective tissue during long time low temperature cooking

Meat Science ◽  
2019 ◽  
Vol 153 ◽  
pp. 109-116 ◽  
Author(s):  
María E. Latorre ◽  
María I. Palacio ◽  
Diego E. Velázquez ◽  
Peter P. Purslow
Keyword(s):  
Low Temperature ◽  
Connective Tissue ◽  
Heat Stability ◽  
Specific Effects ◽  
Long Time

Terrestrial models for extraterrestrial life: methanogens and halophiles at Martian temperatures

2006 ◽  
Vol 5 (2) ◽  
pp. 89-97 ◽  
Author(s):  
I.N. Reid ◽  
W.B. Sparks ◽  
S. Lubow ◽  
M. McGrath ◽  
M. Livio ◽  
...  
Keyword(s):  
Low Temperature ◽  
Extracellular Polymeric Substances ◽  
Halophilic Archaea ◽  
Methanosarcina Acetivorans ◽  
Extraterrestrial Life ◽  
Antarctic Species ◽  
Cold Temperatures ◽  
Cold Adapted ◽  
Cold Environments ◽  
The Galaxy

Cold environments are common throughout the Galaxy. We are conducting a series of experiments designed to probe the low-temperature limits for growth in selected methanogenic and halophilic Archaea. This paper presents initial results for two mesophiles, a methanogen, Methanosarcina acetivorans, and a halophile, Halobacterium sp. NRC-1, and for two Antarctic cold-adapted Archaea, a methanogen, Methanococcoides burtonii, and a halophile, Halorubrum lacusprofundi. Neither mesophile is active at temperatures below 5 °C, but both cold-adapted microorganisms show significant growth at sub-zero temperatures (−2 °C and −1 °C, respectively), extending previous low-temperature limits for both species by 4–5 °C. At low temperatures, both H. lacusprofundi and M. burtonii form multicellular aggregates, which appear to be embedded in extracellular polymeric substances. This is the first detection of this phenomenon in Antarctic species of Archaea at cold temperatures. The low-temperature limits for both psychrophilic species fall within the temperature range experienced on present-day Mars and could permit survival and growth, particularly in sub-surface environments. We also discuss the results of our experiments in the context of known exoplanet systems, several of which include planets that intersect the Habitable Zone. In most cases, those planets follow orbits with significant eccentricity, leading to substantial temperature excursions. However, a handful of the known gas giant exoplanets could potentially harbour habitable terrestrial moons.

scholarly journals Heat inactivation of the extracellular proteinase from Pseudomonas fluorescens 22F: inactivation during heating up and cooling periods

1999 ◽  
Vol 66 (3) ◽  
pp. 467-472 ◽  
Author(s):  
ERIX P. SCHOKKER ◽  
MARTINUS A. J. S. VAN BOEKEL
Keyword(s):  
Pseudomonas Fluorescens ◽  
Thermal Inactivation ◽  
Heating Temperature ◽  
Kinetic Modelling ◽  
Residual Activity ◽  
Heat Inactivation ◽  
Extracellular Proteinase ◽  
Inactivation Curve ◽  
Heating Up ◽  
Kinetics Of

We have reported previously on the kinetics of thermal inactivation at 80–120°C of the extracellular proteinase from Pseudomonas fluorescens 22F (Schokker & van Boekel, 1997, 1999b). During these studies, we noted some inactivation during the heating up and cooling periods, but allowed for this by calculating the residual activity as a fraction of the activity after the heating up period of 2 min followed by cooling to 0°C. However, it may be of interest to evaluate the extent of inactivation during these heating up and cooling periods. If the temperature dependence of the reaction rate behaves according to Eyring's theory, inactivation would, of course, be slower than at the final heating temperature. However, during the heating and cooling of the enzyme solution, the temperature also passes the region in which autoproteolysis occurs (Schokker & van Boekel, 1998a). Prolonged residence time in the critical zone for autoproteolysis may cause increased inactivation, as has been demonstrated in electrophoresis experiments for proteinases from other Ps. fluorescens strains (Barach & Adams, 1977; Richardson, 1981; Diermayr et al. 1987). Consequently, the inactivation during the first few minutes would be dependent on factors influencing both autoproteolytic and thermal inactivation.In most of our heating experiments (Schokker & van Boekel, 1997, 1999b), inactivation during heating up was relatively rapid compared with inactivation at the final heating temperature, leading to a biphasic inactivation curve. This was also found for proteinases from many other Ps. fluorescens strains. In some studies the inactivation during heating up was not taken into account when analysing the kinetics of thermal inactivation (Patel et al. 1983; Yan et al. 1985; Fairbairn & Law, 1986), which led to misinterpretation of the mechanism or the kinetic values. Others explained the biphasic inactivation curve by autoproteolysis (Barach & Adams, 1977; Richardson, 1981; Stepaniak & Fox, 1983; Kroll & Klostermeyer, 1984; Diermayr et al. 1987), or stabilization by Ca2+ of a small portion of the proteinase to heat inactivation (Stepaniak & Fox, 1983; Azcona et al. 1988).In this paper we discuss the influence of protein, enzyme purification and Ca2+ activity on inactivation during the heating up and cooling periods. The aim of this study was to determine, using kinetic modelling, whether the inactivation during heating up and cooling periods could be explained by autoproteolysis and thermal inactivation, or whether other mechanisms are involved in the strong initial inactivation.

Heat stability of plasmin (milk proteinase) and plasminogen

1986 ◽  
Vol 53 (2) ◽  
pp. 259-269 ◽  
Author(s):  
Efstathios Alichanidis ◽  
Julia H. M. Wrathall ◽  
Anthony T. Andrews
Keyword(s):  
Blood Plasma ◽  
Whey Proteins ◽  
Residual Activity ◽  
Skim Milk ◽  
Heat Stability ◽  
Heating Time ◽  
Heat Inactivation ◽  
Plasmin Activity ◽  
Sh Groups ◽  
Substrate Protection

SUMMARYThe effect of heating on plasmin activity in various media, including phosphate buffer pH 7·0, skim milk, blood plasma, solutions of casein and solutions of whey proteins were investigated. Plots of log residual activity υ. heating time were linear at all temperatures from 63 to 143 °C. In buffer solutions the presence of casein led to substantial substrate protection, the Arrhenius plots being linear both in the presence and absence of casein. The activation energy, Ea, for the inactivation reaction, was 62·4 kJ/mol in buffer alone and 58·4 kJ/mol with casein present at 25 mg/ml. In skim milk, despite the presence of casein at a similar concentration, plasmin was no more stable to heat than in buffer alone, and a curved Arrhenius plot was obtained indicating a more complex inactivation mechanism. Heating in the presence of proteins having free -SH groups accelerated the inactivation of plasmin. The role of -SH groups was confirmed by experiments with added α-lactalbumin, in which no free -SH groups occur, and reduced carboxymethylated β-lactoglobulin, both of which were without effect. In blood plasma, plasmin was less stable to heat than in buffer (pH 7·0) or in skim milk. Plasminogen behaved very similarly to plasmin either when activated to plasmin with urokinase before heating or when activated afterwards. A hypothesis is presented to describe the heat inactivation and denaturation of plasmin. Technologically important findings are that in skim milk plasmin was largely unaffected by pasteurization conditions and 30–40% of its activity remained even after ultra high temperature processing conditions.

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