Low Incubation Temperatures Research Articles

Rhamnolipids Enhance Bioremediation of Petroleum-Contaminated Soil

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215952, “Enhancing Bioremediation of Petroleum-Contaminated Soil Using Rhamnolipids: A Combined Laboratory and Field Study,” by Pan Ni, Lehigh University; Yonglin Ren, SPE, Stepan Oilfield Solutions; and Derick G. Brown, Lehigh University, et al. The paper has not been peer reviewed. _ Hydrocarbon spills can occur at various stages of the oil and gas exploration and production process. Treating these spills onsite to avoid more-expensive excavation and incineration processes would be beneficial. The study outlined in the complete paper aims to optimize the use of rhamnolipid biosurfactants for enhancing the bioremediation of hydrocarbon-contaminated soil. The goal of this work was to explore the effects of rhamnolipid application on hydrocarbon degradation rate under both laboratory and field conditions and to examine the effects of this treatment on the indigenous soil microorganism population. Introduction The authors write that, to the best of their knowledge, previous research studies on rhamnolipid-based soil remediation focused on either laboratory or field tests and that comparison between laboratory-scale and field-scale tests is overlooked but necessary for practical applications. Materials and Methods Materials and Chemicals. The soil used for this work (23 kg for the laboratory test, 10 metric tons for the field test) was obtained from a contaminated site in Longford Mills, Canada. The soil properties are presented in Table 1 of the complete paper. The rhamnolipid stock solution featured 9.8 wt% rhamnolipid blends in deionized water. Another commercial remediation agent (enzyme-based) was used in the field test to compare with the performance of rhamnolipid. Ammonium chloride (NH4Cl) and potassium hydrogen phosphate (K2HPO4) also were used along with sodium hydroxide (NaOH). Experimental Setup. Both laboratory and field tests were ex-situ tests using simulated soil piles. The laboratory test was conducted for 193 days. For the laboratory experiments, an aerobic/anaerobic respirometer system equipped with a low-temperature incubator was used to monitor the in-situ oxygen uptake inside eight reactors (Fig. 1). Each reactor contained 250 g of soil with rhamnolipid doses of 0, 0.1, 0.5, and 1 g/kg. The temperature was set to 25°C. Inside each reactor was placed 10 mL of 4-M NaOH in a 20-mL glass beaker to adsorb the produced CO2. A parallel set of eight reactors was prepared and operated under the same conditions. The nutrients of nitrogen and phosphorous (NH4Cl and K2HPO4) were added at specific times based on the oxygen uptake rate monitored by the respirometer. To avoid the possible inhibition of the microbes in the soil as a result of high ionic strength (greater than 160 mM) in the soil pore water, NH4Cl and K2HPO4 were added so that the molar concentration in the soil pore water did not exceed 100 mM. The field test is being conducted in Longford Mills, Ontario, Canada, and is ongoing at the time of writing. For the field test, 10 metric tons of soil were mixed to achieve homogeneity before the preparation of the soil piles. Five different treatment conditions were examined using duplicate soil piles (10 piles total), with each consisting of 1 metric ton of soil. Nutrient addition was similar to that used in the laboratory tests. Temperature and moisture were monitored every few days at five points in each soil pile, and the pH was monitored once every month at five points.

Assessment of Survival Kinetics for Emergent Highly Pathogenic Clade 2.3.4.4 H5Nx Avian Influenza Viruses.

High pathogenicity avian influenza viruses (HPAIVs) cause high morbidity and mortality in poultry species. HPAIV prevalence means high numbers of infected wild birds could lead to spill over events for farmed poultry. How these pathogens survive in the environment is important for disease maintenance and potential dissemination. We evaluated the temperature-associated survival kinetics for five clade 2.3.4.4 H5Nx HPAIVs (UK field strains between 2014 and 2021) incubated at up to three temperatures for up to ten weeks. The selected temperatures represented northern European winter (4 °C) and summer (20 °C); and a southern European summer temperature (30 °C). For each clade 2.3.4.4 HPAIV, the time in days to reduce the viral infectivity by 90% at temperature T was established (DT), showing that a lower incubation temperature prolonged virus survival (stability), where DT ranged from days to weeks. The fastest loss of viral infectivity was observed at 30 °C. Extrapolation of the graphical DT plots to the x-axis intercept provided the corresponding time to extinction for viral decay. Statistical tests of the difference between the DT values and extinction times of each clade 2.3.4.4 strain at each temperature indicated that the majority displayed different survival kinetics from the other strains at 4 °C and 20 °C.

An Ultra-broadband Metallic Plasmonic Antenna for Ultrasensitive Molecular Fingerprint Identification.

Near-field enhanced mid-infrared light-matter interactions via metallic plasmonic antennae (PA) have attracted much attention but are inevitably limited by the detuning between their narrow band and the broad applied spectral range. Here, we develop a new low-temperature incubation synthetic method to acquire uniform Ag microparticles (MPs) with numerous hotspots. Their plasmonic band is remarkably extended by the plasmonic coupling of numerous hotspots and covers the entire mid-infrared range (400-4000 cm-1). Hence, the almost complete molecular fingerprint of 4-mercaptobenzonitrile was successfully probed for the first time via resonant surface-enhanced infrared absorption (rSEIRA), and the rSEIRA spectra of different essential amino acids were further detected and exhibit a high spectral identification degree assisted by machine learning. This work changes the inertia perception of "narrow band and large size but small hotspot area" of mid-infrared metallic PA and paves the way for the ultrasensitive mid-infrared optical sensing.

Lipid Quality Assessment of Virgin Coconut Oil Produced with Different Blanching Methods

Virgin Coconut Oil (VCO) is prone to oxidation due to the natural enzymes present in the coconut. Blanching has been studied to inactivate lipase and peroxidase enzymes that create deterioration in the product. Adding citric acid in hot water during blanching resulted in a higher quality product due to complexing agent properties to chelate metal substances and lowering the pH to reduce the enzymatic activities of the products. This research aims to analyze the effect of different blanching methods on VCO's lipid quality, antioxidant properties, and total phenolic content. Fresh coconut was subjected to water blanching at 95ºC for 5 minutes and 80ºC for 10 minutes with and without 0.05% citric acid addition. After that, VCO was produced using the chilling thawing method, which combines centrifugation and low-temperature incubation. VCO was analyzed in the free fatty acid (FFA), iodine value (IV), peroxide value (PV), TBARS value, the antioxidant activities by ABTS and DPPH, and total phenolic content (TPC). The results showed that water blanching with 0.05% citric acid at 80ºC for 10 minutes obtained better lipid quality compared to control with high IV (6.612±0.085 g iodine/g sample), low FFA (0.0241±0.0023 mg KOH/g sample), and low TBARS value (2.76±0.23 mg MDA/g sample). However, there is a contrary result between antioxidant activities and TPC that might reveal exciting findings. Despite a decrease in the antioxidant activities (DPPH: 39.93±3.11%RSA, ABTS: 9.80±0.91%RSA), the TPC value was increased (9.16±1.56 mg GAE/g sample). Therefore, hot water blanching with 0.05% citric acid addition can be conducted as a pre-treatment in the production of VCO to maintain the lipid quality, even though there is a contradiction in the TPC and antioxidant results.

Manipulation Strategy to Increase Expression Level of Soluble Recombinant Protein Penicillin G Acylase (PGA) in Bacterial Host Escherichia coli: A Review Article

The strategy of producing PGA on a massive scale with high levels of soluble protein can be through recombinant genetic techniques and expressed in a certain host. E. coli is still a popular bacterial host to produce a recombinant protein which has advantages such as fast growth, low production cost, and high expression rate. Apart from its advantages, E. coli as a production host also has disadvantages including the expression of recombinant proteins often failing to form the proper folding conformation which makes the protein biologically inactive. Many strategies can be developed to overcome these problems, such as the selection of the host strain (E. coli HB101 & JM109), fusion protein to enhance the recovery of soluble protein (MBP & NusA), optimization of fermentation (low-temperature incubation), and optimization of the protein isolation process for the recovery of active PGA (Freeze-thawing method).

Acid-responsive polydiacetylene-Na+ assemblies with unique red-to-blue color transition

Polydiacetylenes (PDAs), conjugated and stimuli-responsive polymers, are of interest for colorimetric sensing technologies. Commercially available PDAs with carboxylic headgroup do not show any colorimetric response to acid. To achieve acid-responsive property, the headgroups of PDAs are often modified with some functional moieties, involving complicated synthetic processes. This contribution presents a facile approach to develop acid-responsive materials via co-assembly of PDA and excess sodium hydroxide (NaOH). After low-temperature incubation and photopolymerization, the mixtures of 10,12-tricosadiynoic acid (TCDA) and NaOH develop into red-phase poly (TCDA-Na+) assemblies. A unique red-to-blue color transition occurs when the poly (TCDA-Na+) assemblies are exposed to hydrogen chloride (HCl) acid both in aqueous solution and gas phase. Increasing the concentrations of NaOH and TCDA monomer during the self-assembly process affects the molecular organization and morphologies of the resultant poly (TCDA-Na+) assemblies, which in turn govern the sensitivity to acid. The results of this study offer a simple and inexpensive method for developing acid-responsive PDAs, extending their colorimetric sensing applications.

Studies of polyol production by the yeast Yarrowia lipolytica growing on crude glycerol under stressful conditions

Crude glycerol, the principal by-product of biodiesel production process, was employed as substrate by three wild-type Yarrowia lipolytica strains (ACA-YC 5030, LMBF 20 and NRRL Y-323). Stressful conditions (low pH value = 2.0 ± 0.3, low incubation temperature T = 20 ± 1 °C, non-aseptic conditions) were employed. Interesting production of yeast biomass and polyols (viz. erythritol, mannitol and arabitol) was noted at pH = 2.0 ± 0.3 and T = 20 ± 1 °C. Strains failed to produce significant quantities of cellular lipid, while variable quantities of intra-cellular polysaccharides were produced. Fermentations under previously pasteurized media supported significant biomass and polyols production for most of the tested strains, while only one strain (NRRL Y-323), managed to produce polyols at media that were not previously thermally treated at all. The production of mannitol was favored at low initial glycerol (Glol0) concentrations, whereas higher Glol0 quantities favored the biosynthesis of erythritol. For the strain NRRL Y-323, highly aerated / agitated bioreactor trials showed different physiological profiles as compared to the respective flask experiments. Finally, in flask experiments with the strain NRRL Y-323 at high Glol0 amounts (≈140 g/L) at low medium pH (=2.0 ± 0.3), a significant production of polyols (=84.2 g/L) with the corresponding remarkable conversion yield on glycerol consumed = 62 % w/w was achieved. Practical applicationRenewable and biodegradable fuels, such as biodiesel, are safer and environmentally friendlier than the conventional petroleum diesel. Glycerol is a cost-effective substrate obtained as the main side-product from biodiesel production process and is currently being employed in the realm of Industrial Microbiology and Biotechnology to produce metabolic products with added value. Current research focuses on using glycerol as a starting substrate for biotechnological conversions aiming at producing, amongst other compounds, polyols, microbial biomass, citric acid, etc. from selected strains of the Generally Recognized Αs Safe (GRAS) yeast Yarrowia lipolytica. In the current investigation therefore, we examined the capacity of new wild-type non-extensively studied strains of this yeast to grow and assimilate this inexpensive substrate. Specifically, we have performed the acclimatization of the mentioned strains to stressful environments (i.e., low pH, low incubation temperature, non-aseptic conditions, etc.) and remarkable quantities of the added-value compounds (polyols, yeast mass, citric acid) were produced.

Study on Improving in the Evaluation of Untreated Specimens in the Decay Resistance Effect of Wood Preservatives

This study emphasizes the importance of verifying the vitality of test fungi through the results of untreated specimens in the evaluation of the efficacy of wood preservatives. However, in many cases, the weight loss of the untreated specimens does not meet the criteria in the Korean standard(KS) test method, so we devised an efficient and simplified test method by cross-applying the American Wood Protection Association (AWPA) standard method. The study found that the feeder strip inoculation method specified in the soil block test(AWPA) was more effective than the KS standard, resulting in a higher weight loss (%) of the wood blocks. Among the strains used, <i>Trametes versicolor</i> KACC54448(white rot fungus) showed weight loss rate of 34.1% and <i>Tyromyces palustris</i> and <i>Fomitopsis pinicola</i> KACC53387(brown rot fungi) showed weight loss rates of 63.9%, 58.0%, respectively. Furthermore, we found that maintaining a relative humidity of around 50% by placing distilled water in a low-temperature incubator was sufficient to create an environment in which the test fungi could decay the wood blocks without using expensive equipment such as a constant temperature and humidity chamber. As a result, it was confirmed that the activity of the test fungi can be increased even under conditions of around 50% relative humidity without the shaking cultivation process of the test fungi.

Development of heat-shock resistance in Legionella pneumophila modeled by experimental evolution.

Because it can grow in buildings with complex hot water distribution systems (HWDS), healthcare facilities recognize the waterborne bacterium Legionella pneumophila as a major nosocomial infection threat and often try to clear the systems with a pasteurization process known as superheat-and-flush. After this treatment, many facilities find that the contaminating populations slowly recover, suggesting the possibility of in situ evolution favoring increased survival in high-temperature conditions. To mimic this process in a controlled environment, an adaptive laboratory evolution model was used to select a wild-type strain of L. pneumophila for survival to transient exposures to temperatures characteristic of routine hot water use or failed pasteurization processes in HWDS. Over their evolution, these populations became insensitive to exposure to 55°C and developed the ability to survive short exposures to 59°C heat shock. Heat-adapted lineages maintained a higher expression of heat-shock genes during low-temperature incubation in freshwater, suggesting a pre-adaptation to heat stress. Although there were distinct mutation profiles in each of the heat-adapted lineages, each acquired multiple mutations in the DnaJ/DnaK/ClpB disaggregase complex, as well as mutations in chaperone htpG and protease clpX. These mutations were specific to heat-shock survival and were not seen in control lineages included in the experimental model without exposure to heat shock. This study supports in situ observations of adaptation to heat stress and demonstrates the potential of L. pneumophila to develop resistance to control measures. IMPORTANCE As a bacterium that thrives in warm water ecosystems, Legionella pneumophila is a key factor motivating regulations on hot water systems. Two major measures to control Legionella are high circulating temperatures intended to curtail growth and the use of superheat-and-flush pasteurization processes to eliminate established populations. Facilities often suffer recolonization of their hot water systems; hospitals are particularly at risk due to the severe nosocomial pneumoniae caused by Legionella. To understand these long-term survivors, we have used an adaptive laboratory evolution model to replicate this process. We find major differences between the mutational profiles of heat-adapted and heat-naïve L. pneumophila populations including mutations in major heat-shock genes like chaperones and proteases. This model demonstrates that well-validated treatment protocols are needed to clear contaminated systems and-in an analog to antibiotic resistance-the importance of complete eradication of the resident population to prevent selection for more persistent bacteria.

Screening of xylanase producing Bacillus species and optimization of xylanase process parameters in submerged fermentation

One of the main process inputs in the microbial enzyme, an environment friendly and an extraordinary catalyst, production is characteristics of the microorganism. This study aimed to screen newly isolated Bacillus species for the xylanase production potentiality and investigate crucial parameters that affect the xylanase producing process. Bacteria samples were isolated from potential agricultural and food sources such as soil, wheat bran, and sourdough. Eight xylanase producing isolates showed 99% homology to Bacillus species according to 16S rRNA sequence analysis. Isolate A67 has been found the best xylanase producer isolate and identified as Bacillus halotolerans DSM 8802. Incubation temperature, initial medium pH, and agitation speed parameters were optimized by RSM in the shake flask scale. The optimum xylanase production points were found as 30 °C, pH 8, and 127.27 rpm under submerged fermentation conditions. Xylanase activity was obtained experimentally as 23.47 U/mL resulting 4.21-fold increase with the statistical optimization. R2 and predicted R2 values that reflects the significance of the designed model were calculated as 0.9964 and 0.9674, respectively. Incubation temperature has been concluded as the most important parameter that affects the xylanase activity for isolate A67. As it has low incubation temperature demand, metabolizes xylan polymer as a carbon source and most of the Bacillus species do not produce any toxin, isolate A67 could have potential for the usage of the lignocellulosic biomass added media to make fermentation cost effective in food-grade xylanase production process.

Screening of exopolysaccharide-producing Enterobacter aerogenes NJ1023 and its cadaverine biosynthesis promotion.

Enterobacter aerogenes, the gram-negative bacteria belonging to the family Enterobacteriaceae, lacks the ability to synthesize chemicals. However, in this study, a strain of Enterobacter aerogenes NJ1023 screened from the soil containing petrochemicals was found to be capable of producing extracellular polysaccharides (EPSs). After purification of the polysaccharide, the chemical composition and physicochemical properties of the polysaccharide were analyzed by UV-Vis spectra, FTIR spectroscopy and GC-MS, etc. The results showed that: The molecular weight of the polysaccharide produced by this strain was only 2.7×103 Da, which was lower than that reported in other polysaccharides from the same genus. The polysaccharide produced by E. aerogenes NJ1023 mainly comprised xylose, glucose, galactose, and N-acetylglucosamine with a molar ratio of 0.27: 4.52: 1.74: 0.2, which differed from those reported from the same genus. The results demonstrated that lower incubation temperatures and shaking speeds were more favorable for EPSs synthesis, while higher incubation temperatures and shaking speeds favored cell growth. Additionally, the EPSs produced by E. aerogenes NJ1023 significantly protected the Escherichia coli cells against cadaverine stress. Overall, the discovery of EPSs produced by E. aerogenes increased the diversity of bacterial polysaccharides and broadened the potential applications of this species.

The effect of road salt (NaCl) treatment on the hatching success of Daphnia magna and Thamnocephalus platyurus

Salinization is an emerging problem for freshwater biodiversity. Road salt treatment results in salinization of local freshwater, influencing its entire ecosystem throughout the year. The present study examines the impact of road salt on the hatching success of two zooplankton species, Daphnia magna and Thamnocephalus platyurus, using pure laboratory lines from MicroBioTest. Hatching success was determined without incubation (T0) and after 3, 7 and 28 days of incubation at 5°C (T3, T7 and T28, respectively), at different NaCl concentrations. The low-temperature incubation was intended to simulate winter conditions - 5°C corresponds to the water temperature at the bottom of the ponds during winter in a temperate climate. The number of hatchings decreased with increasing NaCl concentration for T. platyurus, and decreased rapidly after a crucial value of 7 600 mg NaCl/L for D. magna. At the second hatching (eggs washed after first incubation and put into standard freshwater), D. magna demonstrated a low hatching rate regardless of NaCl concentration, while most T. platyurus hatchings were observed at the highest NaCl concentration; hence, the highest (15 200 mg/L) and lowest (1 900 mg/L) NaCl concentrations resulted in similar total hatching for the two species. The incubation time for three and seven days in NaCl at 5°C had no significant impact on hatching success; however, T28 resulted in significantly lower hatching success at all NaCl concentrations and controls. No significant differences in hatching success were noted if the eggs were first washed after incubation in NaCl and then put into the standard freshwater for hatching.

Contrasting responses to climate variability generate seasonal priority effects between native and invasive forest herbs

Abstract Invasive plants are often characterized by rapid germination and precocious phenology. Theory suggests that early germination may provide invaders with a competitive advantage over slower germinating natives, but the relative contribution of rapid germination versus other intrinsic competitive traits (e.g. rapid growth, high fecundity, broad environmental tolerance) to the success of invaders is poorly understood. Depending on the relationship between germination and competition, shifts in germination phenology due to climate change may increase the dominance of invaders or buffer communities against their impacts. We investigated the link between temperature variation, germination phenology and competitive interactions with a sequence of controlled environment experiments. First, we evaluated the relationships between temperature variation and germination phenology for two herbaceous species found in North American woodlands, the non‐native Hesperis matronalis and native Cryptotaenia canadensis. We then leveraged temperature‐response differences to manipulate the relative germination phenology of these taxa and quantified the effects of their phenological differences on competition. Seeds of the invasive H. matronalis germinated rapidly, reaching 50% germination in under 10 days in all treatment combinations. C. canadensis did not reach 50% germination with less than 7 weeks of cold stratification. However, with more than 10 weeks of cold stratification and low (20/10°C) incubation temperatures, the germination phenology of C. canadensis was well‐matched to that of H. matronalis. When grown together, we found that precocious germination phenology doubled the competitive impact of H. matronalis relative to its other intrinsic competitive traits. Phenological advantage of just 2–3 days relative to C. canadensis was enough to secure competitive dominance at the seedling stage. Synthesis. This study revealed that the mechanistic link between the germination phenology and competitive success of an invasive plant can be strongly mediated by climate sensitivity differences between introduced and native species. Climate change will likely exacerbate these differences, especially in regions where warming reduces cold stratification. Our findings suggest that phenological diversity in native plant communities is an important property of invasion resistance. The relationship between environmental variation, germination dynamics and competition provides a path forward for forecasting climate change impacts on seasonal community assembly and highlights the need to incorporate phenological diversity in restorations.

Flash heating boosts the potential for mechanochemical energy sources for subglacial ecosystems

Subglacial environments harbour a diversity of microbial ecosystems capable of influencing biogeochemical cycles. However, the darkness and isolation of subglacial environments limit the energy sources available for microbial metabolism. A recently recognised energy source for these microbes in wet-based regions is the rock-water reactions that occur after the mechanical fracturing of glacial bedrock. These mechanochemical reactions produce H2 and H2O2 at 0°C from reactions with mineral surface defects (Si• and SiO•) and release Fe from within the mineral structures, providing electron donors and acceptors for microbial metabolism. However, the production of H2O2 and H2 may be underestimated as temperatures at rock abrasion sites can increase substantially above 0°C as glaciers “slip and grind” rocks, potentially accelerating the rates of mechanochemical reactions. Despite this, the effect of rapid heating on subsequent low-temperature mechanochemical reactions has yet to be examined. Here, we investigate H2, H2O2, and Fe production during low-temperature (0 °C) incubations of water with a range of ground rocks and minerals following “flash heating” to 30, 60, or 121 °C. We show that transient increases (as little as 5–10 min of heating) to moderate temperatures (30 or 60 °C) can significantly increase the rate of H2 production, while short-term heating to 121 °C generates larger bursts of H2. In addition, pyrite is easily crushed, potentially releasing large quantities of Fe2+ into subglacial systems and promoting mechanochemical reactions due to the resulting large surface area (10× larger than other materials). We provide the first evidence for H2 production from water reactions with crushed pyrite and suggest that crushed pyrite has a greater influence on subglacial H2O2 production than silicates. We conclude that electron donors in the form of Fe2+ and H2 bursts can be produced in subglacial ecosystems, which may be coupled to substantial concentrations of H2O2 produced from crushed pyrite. This suggests that rock–water mechanochemical reactions may be a greater source of energy for subglacial environments than previously recognised.

Production of exopolysaccharides with a high emulsifying activity using an Idiomarina strain under different conditions of oxygen transfer and temperature

AbstractBackgroundMarine microbial exopolysaccharides are the most significant group of polymeric material biopolymers on earth; they exhibit many potential applications in industrial, medical, and environmental fields, due to their chemical structure, which determines their functional properties. This study aimed to evaluate the production and the emulsifying activity of the exopolysaccharides produced by Idiomarina sp. B7H2 cultured under different oxygen transfer rates (OTR) and incubation temperatures.ResultsIn cultures developed at low incubation temperatures (15 °C), an increase in OTRmax from 4.2 to 8 mmol L−1 h−1 promoted cellular growth and exopolysaccharide production, reaching a dry weight biomass of 7.7 ± 0.03 g L−1 and a maximal exopolysaccharide production of 4.28 ± 0.14 g L−1. In contrast, at high incubation temperature (25 °C) and at high OTRmax of 8 mmol L−1 h−1, a maximal emulsifying activity of 75.5% was obtained. This value was higher with respect to that obtained at the lower OTRmax (4.2 mmol L−1 h−1). However, higher emulsifying activity was not related to the synthesis of exopolysaccharides.ConclusionOverall, our results indicate that by controlling the OTRmax and incubation temperatures it is possible to manipulate the production and the emulsifying activity of the bacterial exopolysaccharide produced by B7H2 strain, mainly carrying out the fermentation process at high incubation temperatures and higher OTRmax. © 2023 Society of Chemical Industry (SCI).

Hippuris vulgaris could replace Myriophyllum aquaticum for efficiently removing water phosphorus under low temperature conditions in China

Phytoremediation is widely used for the restoration of aquatic environments. However, the phytoremediation effects and mechanisms of special submerged species of native aquatic plants, especially under low-temperature conditions, are not yet clear. In this study, two typical submerged plants, Myriophyllum aquaticum (M. aquaticum; an exotic species) and Hippuris vulgaris (H. vulgaris; a native species), in China were investigated for their phosphorus (P) removal efficiencies (REp) and the related mechanisms of phytophysiology and microorganisms in a low-temperature incubator (10 °C during the day and 2 °C at night). At an initial P level of 0.5 mg L−1, the two plants exhibited similar REp, with the highest values (73.5%–92.1%) observed on days 3–6. After 18 days, the residual P concentration in the water was less than the Grade III limit value (0.2 mg L−1; GB 3838–2002). However, M. aquaticum had a faster REp velocity than H. vulgaris at an initial P level of 3.0 mg L−1, which was attributed to the mechanisms of plant and its interactions with microorganisms. Compared to the control group, the superoxide dismutase activity of H. vulgaris was significantly increased and its catalase activity was decreased, whereas for that of M. aquaticum was the opposite. Micro region X-ray fluorescence analysis revealed that there may be synergic absorption effects between P, S, and K, and antagonistic absorption action between P and Mn in H. vulgaris. In addition, Acinetobacter, Novosphingobium and Pseudomonas were enriched at 3.0 mg L−1 P level with these two plants, but Chlorophyta only accumulated with H. vulgaris, respectively. Overall, the native species, H. vulgaris, could replace the exotic M. aquaticum to efficiently remove P from polluted water at low temperatures. These findings provide a theoretical foundation for submerged plants P removal capabilities, and the protection of local ecosystem diversity at low temperatures.

Structural basis for the cold activation and adaptation of an α-agarase from marine bacterium Catenovulum agarivorans STB13

Enzymes have high activity at low temperatures are defined as cold-adapted enzymes, but few enzymes show an activation effect after low-temperature incubation. In this study, we cloned an agarase from the marine bacterium Catenovulum agarivorans STB13 (Ca-AGA) and expressed the protein in Bacillus subtilis. The enzyme exhibited a peculiar cold activation, which was enhanced by 5-fold after incubation at −20 °C or 4 °C for 6 h. Fluorescence and CD spectra studies confirmed the secondary and tertiary structural changes in Ca-AGA at low temperature, which formed compact protein structures after low-temperature treatment. The enzyme also showed outstanding cold adaptation, retaining approximately 60% of its maximum activity at 10 °C. Based on a bioinformatics analysis, the carbohydrate-binding modules (CBMs) and long linker region were presumed to play a crucial role in cold adaptation due to a relatively high percentage of acidic residues and a negative charge density compared to the catalytic domain. A mutation that truncated the linker-CBM region resulted in a 59.97% reduction of the activity at 10 °C. This study describes an α-agarase of cold activation and adaptation in detail, which may have great potential for producing functional agaro-oligosaccharides in food and pharmaceutical industrial applications at ambient temperature.

Utilizing in ovo telemetry to examine the effects of reduced incubation temperature on broiler embryo temperature and subsequent hatchability

The current commercial broiler embryo experiences a rapid metabolism and growth rate and may produce more heat than those of the past. Consequently, it may be beneficial to lower standard incubation temperature for commercial broiler hatching eggs. The purpose of this experiment was to determine if lowering incubation temperature at 12 d of incubation (DOI) would affect embryo temperature (ET) in embryonated Ross 708 broiler hatching eggs. From 0 to 12 DOI, eggs were incubated under standard conditions (37.50°C dry bulb, 29.76°C wet bulb). At 12 DOI, temperature transponders were aseptically placed on the inner air cell membrane to measure air cell temperature (ACT) as an estimate of ET in 120 eggs. The eggs were then randomly assigned to 4 separate still-air incubators, each containing 30 eggs. Two replicate incubators were maintained at a standard (STRT; 37.5°C) or low (LTRT; 35.6°C) temperature treatment between 12 and 21 DOI. A significant positive correlation existed between incubator air temperature (IAT) and ACT across temperature treatment and in the STRT. However, IAT was not significantly correlated with ACT in the LTRT. A significantly higher ACT was observed in the STRT than in the LTRT for 88% of the readings taken between 12 and 21 DOI. Percent egg weight loss (PEWL) between 13 and 17 DOI did not significantly differ between temperature treatments. From 13 to 17 DOI, there was a significant positive correlation between PEWL and ACT in the STRT, however, no significant correlation occurred between PEWL and ACT in the LTRT. Percent hatch of fertile eggs containing live embryos at 12 DOI was 93.3% in the STRT and 100% in the LTRT. However, time of hatch occurred 14 to 19 h later and hatchling BW was lower in the LTRT than in the STRT. Although lowering IAT at 12 DOI may improve hatchability, an associated delay in hatch and a decrease in hatchling BW may not be commercially acceptable.

Effects of ambient temperature and available sugar on bacterial community of Pennisetum sinese leaf: An in vitro study.

The present in vitro study investigated the effects of temperature and available sugar on the bacterial community of Pennisetum sinese leaf during fermentation. P. sinese leaves were cultured in MRS broth containing 0.4 and 1.6 g sugar and incubated at 25°C and 45°C for 9, 18, and 36 h. The results showed that the dominant phyla during sugar fermentation were Firmicutes, followed by Proteobacteria and Bacteroidetes. Compared to a low incubation temperature (25°C), a high incubation temperature (45°C) decreased the relative abundances of Exiguobacterium and Acinetobacter and increased those of Bacillus and Paenibacillus. Leaf samples incubated at 25°C showed higher bacterial alpha diversity indices than those incubated at 45°C. Principal coordinate analysis revealed that the bacterial community structure was altered by the high incubation temperature. Sugar concentration of 1.6 g/50 ml increased the relative abundances of Bacillus and Klebsiella but decreased those of Paenibacillus and Serratia as compared to sugar concentration of 0.4 g/50 ml. pH was the primary factor that influenced the succession of bacterial communities during sugar fermentation in P. sinese leaves. In conclusion, ambient temperatures (25°C and 45°C) and high sugar concentration restructured the bacterial communities on P. sinese leaves by facilitating the dominance of Bacillus and Paenibacillus. This study provided insights into the mechanisms by which bacterial communities on P. sinese leaves are enriched.

Quantification of N and C cycling during aerobic composting, including automated direct measurement of N2, N2O, NO, NH3, CO2 and CH4 emissions

Closing the carbon (C) and nitrogen (N) balance has yet to be achieved in aerobic bioprocess due to current methodological drawbacks in the frequency of sampling and detection and the challenge in direct measurement of instantaneous N2 emission. To address this issue, a novel system was developed enabling simultaneous and online determination of gaseous C and N species (N2, N2O, NO, NH3, CO2 and CH4) from aerobic composting at a high frequency of 120 times·d−1. A helium‑oxygen gas mixture was used to replace the air in the system to enable direct measurement of N2 emission, and three different gas exchange methods were assessed in their ability to minimize atmospheric background N2: 1) the N2-free gas purging method; 2) one cycle of the evacuation-refilling procedure; 3) one cycle of evacuating and refilling followed by N2-free gas purging. Method 3 was demonstrated as an optimum N2-removal method, and background N2 concentrations decreased to ~66 μmol·mol−1 within 11.6 h. During the N2-free gas purging period, low temperature incubation at 15 °C reduced CO2, CH4, NO, N2O and NH3 losses by 80.5 %, 41-fold, 10-fold, 11,403-fold and 61.4 %, respectively, compared with incubation at 30 °C. Therefore, a fast and low-perturbation N2 removal method was developed, namely the evacuating/refilling-low temperature purging method. Notably, all C and N gases exhibited large within-day variations during the peak emission period, which can be addressed by high-frequency measurement. Based on the developed method, up to 97.8 % of gaseous C and 95.6 % of gaseous N losses were quantified over a 43-day compost incubation, with N2 emission accounting (on average) for 5.8 % of the initial total N. This system for high frequency measurement of multiple gases (including N2) provides a novel tool for obtaining a deeper understanding of C and N turnover and more accurate estimation of reactive N and greenhouse gas emissions during composting.