The Effect of Molecular Weight on the Antimicrobial Activity of Chitosan from Loligo opalescens for Food Packaging Applications

The growing requirement for sustainable processes has boosted the development of biodegradable plastic-based materials incorporating bioactive compounds obtained from waste, adding value to these products. Chitosan (Ch) is a biopolymer that can be obtained by deacetylation of chitin (found abundantly in waste from the fishery industry) and has valuable properties such as biocompatibility, biodegradability, antimicrobial activity, and easy film-forming ability. This study aimed to produce and characterize poly(lactic acid) (PLA) surfaces coated with β-chitosan and β-chitooligosaccharides from a Loligo opalescens pen with different molecular weights for application in the food industry. The PLA films with native and depolymerized Ch were functionalized through plasma oxygen treatment followed by dip-coating, and their physicochemical properties were assessed by Fourier-transform infrared spectroscopy, X-ray diffraction, water contact angle, and scanning electron microscopy. Their antimicrobial properties were assessed against Escherichia coli and Pseudomonas putida, where Ch-based surfaces reduced the number of biofilm viable, viable but nonculturable, and culturable cells by up to 73%, 74%, and 87%, respectively, compared to PLA. Biofilm growth inhibition was confirmed by confocal laser scanning microscopy. Results suggest that Ch films of higher molecular weight had higher antibiofilm activity under the food storage conditions mimicked in this work, contributing simultaneously to the reuse of marine waste.     

Hydrosedimentology of nested subtropical watersheds with native and eucalyptus forests

Purpose

Information on the effects of eucalyptus forests on hydrosedimentological processes is scarce, particularly at the catchment scale. Monitoring and mathematical modeling are efficient scientific tools used to address the lack of information for natural resource management and the representation and prediction of those processes. This study evaluates the effects of eucalyptus cultivation on hydrosedimentological processes in watersheds and to use the Limburg soil erosion model (LISEM) to represent and predict hydrological processes.

Material and methods

The study was conducted in two forested watersheds: the main watershed (94.46 ha) and a nested sub-watershed (38.86 ha), both cultivated with eucalyptus and residual riparian native forest, located in southern Brazil. Hydrosedimentalogical monitoring was conducted from 16th February 2011 to 31st December 2012, and LISEM model calibrations were performed on the bases of six storms events.

Results and discussion

The sediment yield for 2011 was 41.6 Mg km^?2 and 38.5 Mg km^?2 for the watershed and sub-watershed, respectively. An extreme event in 2012 provided greater sediment yield for the sub-watershed (99.8 Mg km^?2) than that for the watershed (51.7 Mg km^?2). Rainfall events with a greater maximum intensity generated rapid discharge and suspended sediment concentration responses in the sub-watershed due to the smaller drainage area and steeper landscape. In the main watershed, the accumulation of flood waves occurred for most events, with less steep hydrographs, and a later occurrence of the discharge peak after that of the sub-watershed. The LISEM adequately reproduced the peak discharge and runoff for the calibrated events; however, the peak time and the shape of the hydrograph were not adequately represented.

Conclusions

The hydrosedimentological patterns of the watershed and sub-watershed, both cultivated with eucalyptus, was characterized by sedimentographs preceding hydrographs during rainfall–runoff events where scale effects occur, with maximum discharge and specific sediment yield greater in the watershed than that in the sub-watershed. Empirical models based on hydrologic variables may be used for estimating the suspended sediment concentration and sediment yield. Therefore, LISEM may be used for the prediction of hydrological variables in these forested watersheds.     

Functional feed assessment on Litopenaeus vannamei using 100% fish meal replacement by soybean meal, high levels of complex carbohydrates and Bacillus probiotic strains

Functional feed supplemented with alternative-economic nutrient sources (protein, carbohydrates, lipids) and probiotics are being considered in shrimp/fish aquaculture production systems as an option to increase yield and profits and to reduce water pollution. In this study the probiotic potential to formulate functional feeds have been evaluated using four dietary treatments: Treatment 1 (B + Bs); Bacillus subtilis potential probiotic strain was supplemented to a soybeanmeal (SBM)-carbohydrates (CHO) basal feed. Treatment 2 (B + Bm); Bacillus megaterium potential probiotic strain was supplemented to the same SBM-CHO basal feed. In Treatment 3 (B); SBM-CHO basal feed was not supplemented with probiotic strains. Treatment 4 (C); fishmeal commercial feed (FM) was utilized as positive control. Feeding trials evaluated the survival, growth, and food conversion ratio and stress tolerance of juvenile Litopenaeus vannamei (Boone) Pacific white shrimp. Best overall shrimp performance was observed for animals fed with Treatment 1 (B+Bs); additionally, stress tolerance and hemolymph metabolites also showed the best performance in this treatment. SBM-CHO basal feed not supplemented with probiotic strains (B) presented smaller growth and lower feed conversion ratio (FCR). Shrimps fed with the fishmeal commercial feed (C) presented the lowest stress tolerance to high ammonia and low oxygen levels. Specifically selected B. subtilis strains are recommended to formulate functional and economical feeds containing high levels of vegetable; protein and carbohydrates as main dietary sources in L. vannamei cultures.     

Allergenic Content of New Alimentary Pasta Made of Lentils Compared with Lentil Seeds and Analysis of the Impact of Boiling Processing

Plant Foods for Human Nutrition - There is growing interest in legumes such as lentil as healthy ingredients in gluten-free products. In that respect, foods based on lentils, like alimentary pasta,...     

Effect of natural and controlled fermentation on chemical composition and nutrient dialyzability from beans (Phaseolus vulgaris L.)

The effect of natural and controlled fermentation with an inoculum of Lactobacillus plantarum and additional thermal treatment (dry heat at 120 degrees C for 20 min) on the availability of N, P, Fe, Cu, Zn, Ca, and Mg from Phaseolus vulgaris L. var. carrilla was estimated using an in vitro method based on equilibrium dialysis. Natural and controlled fermentations caused significant reductions in the pH and phytate content (36%) of the bean flours, with a concomitant increase in the titratable acidity and free phosphorus content, and had no effect on the other nutrients studied. The percentage of dialyzable N, P, Cu, and Mg was significantly improved by both types of fermentation, whereas Zn dialyzability was significantly reduced. The greatest reduction was observed for the bean flour fermented with an inoculum of L. plantarum. The percentage of dialyzable Fe improved significantly as a result of natural fermentation but was not affected by controlled fermentation. The application of dry heat at 120 degrees C for 20 min caused a significant increase in Fe dialyzability and a further reduction in the percentage of dialyzable Zn in fermented bean flours but did not affect the dialyzability of the other nutrients studied.     

Characterization of commercial iron chelates and their behavior in an alkaline and calcareous soil

Iron deficiency is a common problem for many plants grown in alkaline and calcareous soils. To correct this problem, iron is supplied to plants as chelates. Several iron chelates are sold under diverse trademarks with different characteristics. This work evaluated 18 commercial products containing the most representative chelated iron sources used in agricultural practice in Spain when the study was done, namely the ferric chelates of EDDHA, EDDHMA, EDDCHA, EDDHSA, EDTA, and DTPA. The chelates were comprehensively characterized and quantitated by several techniques, including several chromatographic methods. Iron and chelate dynamics in soil were also studied in a model alkaline and calcareous soil. Results indicate that, in this model soil, among the different iron compounds studied only FeEDDHA and analogues have the capacity to maintain soluble iron in soil solution over time. These results are in agreement with general experience under field conditions. Furthermore, among the different ortho-ortho isomers of FeEDDHA's, FeEDDHSA and FeEDDCHA showed greater capacity than FeEDDHA and FeEDDHMA to maintain the chelated iron in soil solution over time.     

Comparative transcriptional analyzes of Xanthomonas citri subsp. citri reveal mechanisms of adaptation and bacterial virulence in the early stage of citrus canker disease

European Journal of Plant Pathology - The Allium cepa L. (onion) crop is affected by leaf blight disease caused by Stemphylium vesicarium; the shifts that S. vesicarium infection causes in the...     

Atripes paspali gen. et sp. nov. (Magnaporthaceae) causing take-all disease on Paspalum guenoarum in Brazil

In Brazil, Paspalum species are commonly used in sports lawns, landscape projects, and as forage for livestock. Paspalum guenoarum plants showing symptoms of take-all disease were observed in the state of Rio Grande do Sul, Brazil. The fungus Gaeumannomyces graminis is the only species reported associated with this disease on Paspalum. In recent years, new species of Gaeumannomyces have been proposed based on molecular studies, which demonstrated the existence of a species complex. Take-all affects rice and wheat, but the aetiology of this disease on P. guenoarum is still unknown; this work aimed to elucidate the aetiology of the take-all on P. guenoarum in Brazil and evaluate possible alternative hosts of agricultural importance. Based on combined phylogenetic analyses of ITS, LSU, TEF-1α, and RPB1 sequences, the fungal pathogen was identified as Atripes paspali gen. et sp. nov., which is proposed as a new genus in the Magnaporthaceae family. A representative isolate of A. paspali was inoculated on healthy P. guenoarum plants and reproduced the same symptoms of take-all observed in the field. Furthermore, this fungus is also able to cause take-all on wheat plants; temperature directly affected the incidence and development of the disease in wheat. Take-all on P. guenoarum is caused by A. paspali.     

Validation and use of a qPCR protocol to quantify the spread of Ralstonia solanacearum in susceptible and resistant eucalypt plants

Bacterial wilt caused by Ralstonia solanacearum is a serious disease of eucalypt in humid and high temperature areas worldwide. Spreading of the bacterium in the field or to other nurseries occurs mainly by symptomless infected plant material. The use of pathogen-free propagating material as well as planting of resistant genotypes are currently the only strategies used for disease control. Therefore, a reliable and sensitive method for detection of low titres of R. solanacearum in infected plant tissue is essential for the success of management programmes. In this work, we adapted an efficient intercalating dye-based real-time PCR protocol to detect the bacterium in symptomless eucalypt plants as well as to investigate its movement in eucalypt clones CLR172 and CLR371, which exhibit resistant and susceptible phenotypes, respectively. We found that the bacterium translocates acropetally and basipetally in inoculated but symptomless cuttings of the resistant clone, as in cuttings of the susceptible clone displaying symptoms. Nevertheless, a smaller concentration of bacterial DNA was detected in tissues of the resistant clone. Mature biofilms occluding the xylem vessels were present in the susceptible clone whereas only single cells or small aggregates were observed in the resistant clone. This work contributes to improve our knowledge of the colonization process of R. solanacearum in eucalypt clones with different levels of susceptibility and to understand how the defence mechanisms against bacterial wilt in Eucalyptus work. Our findings could aid in the selection of the most resistant eucalypt clones to be used in wilt disease management programmes.