Synergistic Hydrolysis of Crude Corn Starch by α‐Amylases and Glucoamylases of Various Origins

Four α‐amylases and two glucoamylases from various sources, in eight combinations, were used to study the synergistic hydrolysis of crude corn starch at various temperatures. At 40 and 50°C, the combinations containing Rhizopus mold glucoamylase enhanced hydrolysis of corn starch compared wth that obtained with the combinations from Aspergillus niger. At 60°C, Rhizopus mold combinations gave low reaction yields as the enzyme was inactivated. The differences observed between α‐amylases are smaller, with the exception of Bacillus licheniformis α‐amylase, which presented more than twice the productivity of the other α‐amylases, at all temperatures. In terms of substrate conversion at 5 hr of hydrolysis, the combination of B. licheniformis α‐amylase with Rhizopus mold glucoamylase at 50°C presents 76% substrate conversion, whereas, with all the other combinations, starch conversion was 13–73%. HPLC analysis of the reaction products obtained at 50°C showed that the main product of corn starch hydrolysis was glucose at 85–100%. Further experiments showed that A. niger glucoamylase and B. licheniformis α‐amylase were the only enzymes that retained their initial activity after incubation at the temperatures studied.     

Scale matters: performance of European sea bass,Dicentrarchus labrax,L. (1758), reared in cages of different volumes

The effects of rearing volume on on‐growing European sea bass performance and stress parameters were investigated for the first time in a pilot aquaculture farm. Fish were held under the same initial stocking densities in triplicate net‐pen cages of different sizes (1.4, 45 and 252 m³) for a period of 8 months. Results showed significant differences among the experimental groups in most parameters tested, with better performance in the two larger rearing volumes. In particular, growth rate showed a linear association with rearing volume, being 0.68 g day^?1 for the large cage group, 0.56 g day^?1 and 0.32 g day^?1 for the medium and the small groups respectively. The feed conversion ratio and per cent survival (%) were also better in the large cage group. Fish reared in the small and medium‐sized cages showed higher plasma cortisol concentrations than those reared in large cages, which showed low basal cortisol concentrations. Additionally, after an acute chasing stress challenge, fish in the large and small groups, but not the medium group, showed increased cortisol concentrations. Differences also occurred in the ratio of the expression of cortisol receptors, namely the mineralocorticoid (mr) and glucocorticoid receptors (gr). In specific, the ratio of mr to grmRNA expression in the liver was higher in fish reared in the small cages. These findings verify that experimental scale significantly affects experimental results and is a critical factor for the interpretation of results.     

Interrelationship among and repeatability of seven stability indices estimated from commercial cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) variety evaluation trials in three Mediterranean countries

Multi-environment trial data are required, to obtain variety stability performance parameters as selection tools for effective cultivar evaluation. The interrelationship among seven stability parameters and their association with mean yield, along with the repeatability of these parameters across consecutive years was the objective of this study. Cottonseed yield data of 31 cotton cultivars, proprietary of Delta and Pine Land Co and other companies, evaluated in 20 locations over the 1999–2005 year period in Greece, Spain and Turkey were used for combined analysis of variance in four datasets. Across locations in a single evaluation year (dataset A), across locations in each of two single consecutive evaluation year (dataset B), across locations and two consecutive years (dataset C) and across locations and three consecutive years (dataset D). For each dataset, cultivar phenotypic variance was appropriately partitioned in its components and the h² and component estimated. Furthermore, following the appropriate stability analysis and AMMI1 along with the GGE Biplot distance (GGED) and instability (GGEIN) parameters were obtained. The interrelationship among the parameters and their association with mean yield based on Spearman rank correlation was studied in each of the seven single evaluation years (dataset A). Rank correlation coefficients were also used as estimates of the repeatability of these stability parameters across consecutive year combinations (dataset B, C and D). The parameters GGED and YS_i were consistently highly correlated with each other and mean yield in five out of seven single evaluation years. The data provided evidence that single year evaluation across locations might be sufficient to reliably rank cotton cultivars, based on mean yield along with GGED and YS_i. Combined analysis across two consecutive years (dataset C) was more effective as compared to single year evaluation. GGED was relatively more repeatable than YS_i and mean yield in single (dataset B) and 2-year comparisons (dataset C). Although GGED is an index depended and proportional to yield, provides a superior way to integrate mean performance and stability into a single measure, which can be assessed visually on biplots. Regarding the other stability parameters, the results were contradicting and of low repeatability across single years and two consecutive years. Cultivar evaluation combined across locations in 3 years did not improve the repeatability of cultivar variance effects but resulted in very high repeatability of GGED, YS_i and mean yield.     

Assessment of the Possible Mutagenic Potential in Drinking Water Samples from Areas in SW Greece,Using the Ames Microsome Mutagenicity Assay

The mutagenic activity of thirty drinking water samples from 30 small communities in the districts of Achaia and Elia located in SW Greece as well as seven samples from the city of Patras (in the same area with 153 000 inhabitants) were examined during the years 1994–1995. The organic extract from 300–400 L of water was collected from each station and was subjected to the Ames mutagenicity assay using four genetically mutated strains of Salmonella typhimurium (TA97a, TA98, TA100, TA102) with or without metabolic acivation (10% S9). At the same time, several physicochemical characteristics of the samples were measured. Criteria for the mutagenic activity of the water samples were based on the two-fold rule and the significant non-zero slope of the linear dose response curve. In 84% of the samples at least one assay fulfilled both the two-fold rule and the significant slope and could be considered mutagenic. Thirty nine per cent (39%) of the samples were considered to show a strong mutagenic response, as in these samples the simultaneous satisfaction of the two criteria was observed in at least 3 assays out of eight. The mutagenic response was shown to be higher in chlorinated compared to untreated water samples. In the city of Patras, drinking water showed an increased mutagenic potential in comparison to an earlier study, regardless of the disinfecting process (chlorine or chlorine dioxide). The authors discuss the possibility that mutagenic activity was dependent on interaction among various organic compounds, metals and other water constituents.     

Plant regeneration of Nerium oleander L. from alginate-encapsulated shoot explants after short-term cold storage

In this study, an efficient protocol for the regeneration of encapsulated explants of oleander (Nerium oleander L.) has been developed. Shoot tips and 1st nodal segments below the shoot tip, from in vitro-derived oleander microshoots, were encapsulated in 2.5% sodium alginate prepared in liquid MS sucrose-free nutrient medium and hardened in 50 mM of calcium chloride producing solid beads, uniform in shape. These artificial seeds, irrespective of their maintenance under light or in darkness, germinated at frequencies of 38.8–42.2%, producing 3.0–3.3 microshoots per bead. In the case of using 100 mM of calcium chloride for hardening, the beads were firm, of uniform globular shape and suitable for handling, exhibiting a germination response of 68.9%. Encapsulated shoot tip explants, following storage at 4°C for 8 weeks, exhibited a higher regeneration response (60.0%) than non-encapsulated similar explants stored under the same conditions (11.1%). Microshoots, excised from cold-stored encapsulated explants after germination, rooted easily in agar-solidified MS medium with 2 μΜ IBA and after their transplantation into a peat-perlite substrate (3:1, v/v), were acclimatised successfully and established in the greenhouse with minimal losses. The present encapsulation procedure could be applied as an alternative method of micropropagation of desirable elite clones of oleander.     

Left-right dynein motor implicated in selective chromatid segregation in mouse cells

During cell division, copies of mouse chromosome 7 are segregated selectively or randomly to daughter cells depending on the cell type. The mechanism for differential segregation is unknown. Because mouse left-right dynein (LRD) gene mutations result in randomization of visceral organs' laterality, we hypothesized that LRD may also function in selective chromatid segregation. Indeed, upon knock-down by RNA interference methods, LRD depletion disrupts biased segregation. LRD messenger RNA presence or absence correlates with the observed segregation patterns. This work supports the claim that LRD functions in a mechanism for selective chromatid segregation.     

Evolution of volatile byproducts during wine fermentations using immobilized cells on grape skins

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae cells on grape skins. Repeated batch fermentations were conducted using this biocatalyst as well as free cells, at 25, 20, 15, and 10 degrees C. Solid phase microextraction (SPME) was used in monitoring the evolution of volatile byproducts. The effect of immobilization and temperature on evolution patterns of volatiles was obvious. The major part of esters was formed after consumption of 40-50% of the sugars. Similar processes were observed for amyl alcohols and 2-phenylethanol, whereas 1-propanol and 2-methyl-1-propanol were formed during the whole alcoholic fermentation period at an almost constant formation rate. Acetaldehyde and acetoin were synthesized in the early stages of fermentation. Afterward, their amount decreased. In most cases, immobilized cells exhibited higher formation rates of volatiles than free cells. The final concentration of esters was higher in wines produced by immobilized biocatalyst. Their amount increased with temperature decrease. The opposite was observed for higher alcohols.     

A method for measuring cellular characteristics of wood

Summary A new method is presented for measuring fractional cell wall area by use of photomicrographs of cross sections of wood. The method is geometric in approach and measures, within a delineated area of complete cells, compound cell wall thickness of adjoining cells in systematically or randomly selected locations. In comparison to point sampling (dot grid method), applied with single or repeated trials, the proposed method is shown to require a lesser number of samples for the same statistical accuracy. In addition to fractional cell wall area, the method serves to determine mean cell and lumen area (or diameter).     

The role of glutathione S-transferases in the detoxification of some organophosphorus insecticides in larvae and pupae of the yellow mealworm,Tenebrio molitor (Coleoptera: Tenebrionidae)

The correlation between the natural levels of glutathione S-transferase (GST) and the tolerance to the organophosphorus insecticides parathion-methyl and paraoxon-methyl, as well as the interaction of affinity-purified enzyme and the insecticides were investigated in order to collect further information on the role of the glutathione S-transferase system as a mechanism of defence against insecticides in insects. The studies were carried out on the larvae and pupae of the coleopteran Tenebrio molitor L, which exhibit varying natural levels of GST activity. Stage-dependent susceptibility of the insect against insecticides was observed during the first 24 h. However, 48 h after treatment, the KD₅₀ value increased significantly due to the recovery of some individuals. Simultaneous injection of insecticide with compounds which inhibit GST activity in vitro caused an alteration in susceptibility of insects 24 or 48 h post-treatment, depending on stage and insecticide used. Inhibition studies combined with competitive fluorescence spectroscopy revealed that the insecticides probably bind to the active site of the enzyme, thus inhibiting its activity towards 1-chloro-2,4-dinitrobenzene in a competitive manner. High-performance liquid chromatography and gas chromatography revealed that T molitor GST catalyses the conjugation of the insecticides studied to a reduced form of glutathione (GSH). From the above experimental results, it is considered that GST offers a protection against the organophosphorus insecticides studied by active site binding and subsequent conjugation with GSH. © 2001 Society of Chemical Industry