Release Of Intracellular Compounds Research Articles

Non-thermal treatments of strawberry pulp: The relationship between quality attributes and microstructure

The relationship between quality attributes and microstructure in strawberry pulp after pasteurization (PS), ultrasound (US), electron beam irradiation (EB), and high pressure (HP) treatments was investigated. The results showed that US treatment decreased the viscosity to the lowest by 80.15% and increased the a* value, cloudy stability, and contents of titratable acid, total soluble solid, organic acids, total phenols, total flavonoids, and total anthocyanins (TAC), as well as its antioxidant capacity, due to the decrease in particle size, the destruction of microstructure, and the release of intracellular compounds. US and EB treatments could maintain the volatile compounds. The greatest deterioration in TAC and volatile compound content was found in the pulp treated with PS and HP treatments. HP treatment was beneficial to the enhancement of apparent viscosity, organic acids, and soluble sugar. These results provided insights into the enhancement of quality attributes in strawberry pulp due to the microstructure change.

Actinobacteria produce taste and odor in drinking water reservoir: Community composition dynamics, co-occurrence and inactivation models

Taste and odor (T&O) has become a significant concern for drinking water safety. Actinobacteria are believed to produce T&O during the non-algal bloom period; however, this has not been widely investigated. In this study, the seasonal dynamics of the actinobacterial community structure and inactivation of odor-producing actinobacteria were explored. The results indicated that the diversity and community composition of actinobacteria exhibited significant spatiotemporal distribution. Network analysis and structural equation modeling showed that the actinobacterial community occupied a similar environmental niche, and the major environmental attributes exhibited spatiotemporal dynamics, which affected the actinobacterial community. Furthermore, the two genera of odorous actinobacteria were inactivated in drinking water sources using chlorine. Amycolatopsis spp. have a stronger chlorine resistance ability than Streptomyces spp., indicating that chlorine inactivates actinobacteria by first destroying cell membranes and causing the release of intracellular compounds. Finally, we integrated the observed variability in the inactivation rate of actinobacteria into an expanded Chick-Watson model to estimate its effect on inactivation. These findings will deepen our understanding of the seasonal dynamics of actinobacterial community structure in drinking water reservoirs and provide a foundation for reservoir water quality management strategies.

Inactivation of fungal spores in water using ozone: Kinetics, influencing factors and mechanisms

Fungal contamination of drinking water sources is increasingly threatening the environment and human health. In this study, the inactivation of three genera of dominant fungi in drinking water sources using ozone was first reported. The inactivation of the fungal spores by ozone could be divided into two distinct stages: first a rapid reduction in survival, and then the inactivation at a slower rate. The secondary stage inactivation fitted the Chick–Watson model well, and there was no significant difference in the second-order inactivation rate constants of the three fungal spores (0.199–0.209 L mg−1 min−1). The inactivation rate constants of fungal spores by molecular ozone were much lower than those of viruses, which were equivalent to that of Cryptosporidium. The increase in pH and temperature showed a positive effect on the inactivation rate. Damage to cell membranes, leakage of intracellular compounds, and changes of reactive oxygen species and esterase activity in the spores were detected after inactivation. The results indicated that ozone inactivated fungal spores by firstly destroying cell walls and membranes and then causing the release of intracellular compounds. The fungicidal efficiency of ozone was superior to those of chlorine and chlorine dioxide. In addition, the inactivation efficiency of ozone on fungal spores in real water matrices was reduced to 50.7–91.2% of the efficiency in phosphate buffer. In conclusion, ozone showed high efficiency in the inactivation of fungal spores and could be used as an alternative disinfectant for fungal contamination in drinking water sources.

Effect of growth phase of cyanobacterium on release of intracellular geosmin from cells during microfiltration process

During low-pressure membrane treatments of cyanobacterial cells, including microfiltration (MF) and ultrafiltration (UF), there have reportedly been releases of intracellular compounds including cyanotoxins and compounds with an earthy-musty odor into the water, probably owing to cyanobacterial cell breakage retained on the membrane. However, to our knowledge, no information was reported regarding the effect of growth phase of cyanobacterial cells on the release of the intracellular compounds. In the present study, we used a geosmin-producing cyanobacterium, Anabaena smithii, to investigate the effect of the growth phase of the cyanobacterium on the release of intracellular geosmin during laboratory-scale MF experiments with the cells in either the logarithmic growth or stationary phase. Separate detection of damaged and intact cells revealed that the extent of cell breakage on the MF membrane was almost the same for logarithmic growth and stationary phase cells. However, whereas the geosmin concentration in the MF permeate increased after 3 h of filtration with cells in the logarithmic growth phase, it did not increase during filtration with cells in the stationary phase: the trend in the geosmin concentration in the MF permeate with time was much different between the logarithmic growth and stationary phases. Adsorption of geosmin to algogenic organic matter (AOM) retained on the MF membrane and/or pore blocking with the AOM were greater when the cells were in the stationary phase versus the logarithmic growth phase, the result being a decrease in the apparent release of intracellular geosmin from the stationary phase cells. In actual drinking water treatment plants employing membrane processes, more attention should be paid to the cyanobacterial cells in logarithmic growth phase than in stationary phase from a viewpoint of preventing the leakage of intracellular earthy-musty odor compounds to finished water.

Oxidation of Microcystis aeruginosa and Anabaena flos-aquae by ozone: Impacts on cell integrity and chlorination by-product formation

Pre-ozonation of cyanobacterial (CB) cells in raw water and inter-ozonation of settled water can cause CB cell damage. However, there is limited information about the level of lysis or changes in cell properties after ozonation, release of intracellular compounds and their contribution to the formation of disinfection by-products (DBPs). This study aims to: (1) assess the extent of the pre-ozonation effects on CB cell properties; (2) determine the CT (ozone concentration × detention time) values required for complete loss of cell viability; and (3) study the DBPs formation associated with the pre-ozonation of cyanobacterial cells in laboratorial suspensions. To these ends, both Microcystis aeruginosa and Anabaena flos-aquae suspensions were prepared at concentrations of 250,000 cells mL−1 and 1,500,000 cells mL−1 and were subjected to ozone dosages of 0.5, 2.0 and 4.0 mg L−1 at pH 6 and pH 8. A quick and complete loss of viability was achieved for both CB species after exposure (CT) to ozone of <0.2 mg min L−1, although no significant decrease in total cell numbers was observed. Maximum dissolved organic carbon (DOC) releases of 0.96 mg L−1 and 1.63 mg L−1 were measured after ozonation of 250,000 cells mL−1 of M. aeruginosa and A. flos-aquae, respectively. DOC release was found to be pH and ozone dose dependent. Ozonation of CB cells increased formation of trihalomethanes (THM) and haloacetic acids (HAA), mainly for suspensions of A. flos-aquae at pH 8 (by 174% and 65% for THM and HAA respectively). Utilities considering using ozone for oxidising CB cells should weigh out the benefit of CB control with the potential increased formation of chlorinated DBPs.

Preparation of yeast cells for surface analysis by XPS

Analysis of the chemical composition of the surface of microbial cells by X-ray photoelectron spectroscopy (XPS) requires drying. The influence of the sample preparation procedure (washing, freezing, freeze drying, storage) has been examined with brewing yeasts. The recommended procedure involves washing at least once and pouring a concentrated suspension into a vial, precooled at liquid nitrogen temperature. The freeze-drying conditions are not critical provided that no melting occurs; this would cause cell lysis and release of intracellular compounds which alter the XPS results. Prolonged storage of freeze-dried samples prior to surface analysis leads to oxidation of surface groups. The cooling rate is high enough to prevent migration of intracellular constituents to the surface; however removal of surface polymers or appendages during washing or rearrangements of the polymer network at the surface, resulting from freezing, recrystallization or water removal, cannot be excluded.

Effects of hydrodynamic stress on cultured plant cells: A literature survey

In this paper a literature survey is presented on the effects of hydrodynamic stress (“shear stress”) on cultured plant cells. Hydrodynamic stress has mostly negative effects on cells, these effects can be designated as “damage.” Various symptoms of cell damage as damage indicator are discussed: alteration of morphology, release of intracellular compounds, alteration of metabolism and productivity, and loss of viability. A compilation is made of the experimental techniques that have been used to investigate the shear sensitivity of plant cells. From the literature reviewed it is clear that huge differences in hydrodynamic stress sensitivity exist among various plant cell lines. The opinion that plant cells are by all means sensitive to hydrodynamic stress has to be revised. It is concluded that for the development of a productiond system based on plant cells, hydrodynamic stress sensitivity should be determined preferably in a down-scaled version of the production system.