Variability of hydrolysis of β-, αs1-, and αs2-caseins by 10 strains of Streptococcus thermophilus and resulting bioactive peptides

Milk proteins contain numerous potential bioactive peptides, which may be released by digestive proteases or by the proteolytic system of lactic acid bacteria during food processing. The capacity of Streptococcus thermophilus to generate peptides, especially bioactive peptides, from bovine caseins was investigated. Strains expressing various levels of the cell envelope proteinase, PrtS, were incubated with α(s1)-, α(s2)-, or β-casein. Analysis of the supernatants by LC-ESI-MS/MS showed that the β-casein was preferentially hydrolyzed, followed by α(s2)-casein and then α(s1)-casein. Numbers and types of peptides released were strain-dependent. Hydrolysis appeared to be linked with the accessibility of different casein regions by protease. Analysis of bonds hydrolyzed in the region 1-23 of α(s1)-casein suggests that PrtS is at least in part responsible for the peptide production. Finally, among the generated peptides, 13 peptides from β-casein, 5 from α(s2)-casein, and 2 from α(s1)-casein have been reported as bioactive, 15 of them being angiotensin-converting enzyme inhibitors.     

Effects of Protein Concentration,Plasticiser, and pH on the Properties of Protein Films from Whitemouth Croaker (Micropogonias furnieri) Residues

ABSTRACT

Proteins have been used extensively because of their relative abundance, nutritional qualities, and film-forming ability with a good structural integrity and mechanical properties. This study investigated the effects of protein isolate and glycerol concentration and pH on the properties of protein films obtained from Whitemouth croaker (Micropogonias furnieri) residues. The films were evaluated for mechanical properties, thickness, water solubility, water vapor permeability (WVP), and morphological properties. The lowest water solubility of the films occurred at low pHs and low glycerol concentrations. The films had high elongation and higher tensile strength when prepared with higher concentrations of protein isolate, lower concentrations of glycerol, and at lower pHs. The WVP and thickness of the films had a low correlation coefficient. The films were rough and had irregular surfaces. These results indicated that protein isolates from fish of low commercial value can be used as a component of new polymeric films for packaging. However, more studies are needed to assess their barrier action against oxygen, thermal behaviors, and their performance in different types of packaging.     

Brandt's cormorant diet (1994–2012) indicates the importance of fall ocean conditions for northern anchovy in central California

Effective ecosystem‐based management requires a comprehensive understanding of the functional links in the system. In many marine systems, forage species constitute a critical link between primary production and upper trophic level marine predators. As top predators, seabirds can be indicators of the forage species they consume and the ocean processes that influence these populations. We analyzed the diet and breeding success for the years 1994, 2003, 2005, and 2007–2012 of the Brandt's cormorant (Phalacrocorax penicillatus), a piscivorous diving seabird, breeding in central California, to evaluate the extent to which cormorant diet composition relates to prey availability, and how diet composition relates to breeding success and ocean conditions. Cormorant diet was primarily composed of young‐of‐the‐year (YOY) northern anchovy (Engraulis mordax), YOY rockfish (Sebastes spp.), and several species of small flatfish (order Pleuronectiformes). YOY rockfish consumption was positively related to their abundance as measured in a late spring pelagic midwater trawl survey. Northern anchovy appeared to be the most important prey as its consumption was positively related to cormorant breeding success. More northern anchovy were consumed in years where warm‐water conditions prevailed in the fall season before cormorant breeding. Thus, warm ocean conditions in the fall appear to be an important contributing factor in producing a strong year‐class of northern anchovy in central California and consequently a strong‐year class of Brandt's cormorant on the Farallon Islands.     

The effect of root and shoot pruning on early growth of hybrid poplars

Planting stock type and quality can have an important impact on early growth rates of plantations. The goal of this study was to evaluate early growth and root/shoot development of different planting materials in typical heavy clay soils of northwestern Quebec. Using one-year-old bareroot hybrid poplar dormant stock, four planting materials were compared: (1) regular bareroot stock, (2) rootstock (stem pruned before planting), (3) whips (roots pruned before planting), and (4) cuttings (30 cm stem sections taken from the basal portion of bareroot trees, i.e. roots and shoot pruned). Rooted stock types (bareroot and rootstock) produced, on average, 1.2 times larger trees than unrooted stock types (cuttings and whips). However, shoot-pruned stock types (rootstocks and cuttings) reached similar heights and basal diameters as unpruned stock types (bareroots and whips), during the first growing season. Shoot pruning reduced leaf carbon isotopic ratios, suggesting that unpruned stock types were water-stressed during the first growing season. The stress was most likely caused by early leaf development while root growth occurred later in the summer. We conclude that shoot pruning bareroot stock is a useful management option to reduce planting stress without compromising early growth rates of hybrid poplars.     

Spatial distribution,architecture, and development of the root system of Pinus banksiana Lamb. in natural and planted stands

In the province of Québec, Canada, the majority of planted jack pine (Pinus banksiana Lamb.) seedlings are produced in rigid wall containers. More than 95% of them exhibit deformations of the root system which may induce stem instability. Studies of the root architecture of planted jack pine have been limited to a 30 cm radius from the stem, as barely any studies have been devoted to naturally regenerated stands. Moreover, only a few researches have focused on temporal evolution of root systems. The aim of the present study was to characterize the architectural, spatial, and temporal development of jack pine roots in natural and planted stands. Study sites were located in the continuous boreal forest of Quebec. The plantation was done in 1987, so that the trees were 15 years old at the time of sampling. Trees from natural stand had regenerated after a fire in 1983 and were 13–16 years old. The root systems of 14 jack pine trees per site were manually excavated up to a <5 mm diameter, without regard to their distance from the stem. The number, length, diameter, and the spatial and temporal development of roots were analyzed according to three scales of root architecture: the root system, axes, and segments. Overall, the numbers and lengths of roots were higher with planted pines. However, naturally regenerated trees displayed a better distribution of their roots around the stem and at depth, combined with more rapid length growth during the first years. In natural stands, all the trees had a taproot and 30% of the main roots originated at a depth of more than 20 cm, and they are regularly distributed around the stems. Planted trees did not present a taproot and 97% of the main roots originated in the first 20 cm beneath the soil surface. Moreover, 50% of root length was located in one-third of the area surrounding the stems, an area that corresponded to the furrow. Finally, the annual development of lateral roots in planted stand displayed a 5-year delay when compared with natural stand, which also affected maximum growth length and development of the branching pattern. Root distribution and temporal development are known to play a major role in the stability of aerial parts. Seedling production methods, container type, site preparation and planting techniques need to be examined in greater detail in order to assess their effect throughout the development of the root system. It is necessary to compare different sylvicultural practices and with natural/planted stands to gain a clearer understanding of this problem.     

Early growth and nutrition of hybrid poplars fertilized at planting in the boreal forest of western Quebec

In order to maximize growth and diagnose nutritional requirements of hybrid poplars (Populus spp.) grown in the boreal forest of western Quebec, the Diagnosis and Recommendation Integrated System (DRIS) was evaluated in conjunction with N:P ratios of trees fertilized at planting. Three hybrid poplar clones (747210; P. balsamifera × trichocarpa, 915005; P. balsamifera × maximowiczii, and 915319; P. maximowiczii × balsamifera) were fertilized with 18 combinations of nitrogen (N), phosphorus (P) and potassium (K). Fertilizers used were granules of ammonium nitrate (34.5-0-0) at 3 levels (0, 20 and 40 g tree⁻¹ of N), triple-superphosphate (0-45-0) at 3 levels (0, 25 and 50 g tree⁻¹ of P), and potassium sulfate (0-0-50) at 2 levels (0, 20 g tree⁻¹ of K). After two growing seasons, P fertilization was the most effective in promoting growth and 25 g tree⁻¹ increased mean stem volume by 41% compared to unfertilized trees. The predictive accuracy of the N:P and DRIS diagnosis methods was generally reliable, however they failed to predict some co-limitations of N and P.     

Cambial phenology, wood formation and temperature thresholds in two contrasting years at high altitude in southern Italy

Xylogenesis was monitored during 2003 and 2004 in a timberline environment in southern Italy to assess links between temperature, cambial phenology and wood formation on a short-time scale. Wood microcores were collected weekly from May to October from 10 trees of Pinus leucodermis Ant., histological sections were cut with a rotary microtome and anatomical features of the developing and mature tracheids were observed and measured along the growing tree ring. Spring 2003 was hotter than spring 2004, with temperatures up to 2.6 degrees C above historical means. The hotter conditions resulted in an earlier onset of cambial activity and all differentiation phases of about 20 days, resulting in an increased duration of xylogenesis of about 23 days. Air and stem temperatures at which xylogenesis had a 0.5 probability of being active were calculated with logistic regressions fitted on binary responses. In both years, similar thresholds were estimated with daily mean values of 8.2 and 9.5 degrees C for air and stem temperatures, respectively. The observed convergent responses of cambium phenology to temperature during the two contrasting springs confirm the key role of this environmental factor in determining the onset and duration of wood formation in timberline areas. The intra-annual dynamics of ring-width increase differed between years, with significantly narrower rings formed in 2004 than in 2003. These differences were mainly related to cell size because larger earlywood tracheids were produced in 2003. This study demonstrates the plasticity of tree-ring formation in response to high temperatures as a result of modifications in the onset and duration of differentiation.     

Oxygreen process applied on nongerminated and germinated wheat: role of hydroxamic acids

Wheat samples were taken at different stages of germination characterized by their falling number (which is a relevant indicator of germination) from 400 to 60 s. Each batch was treated by the Oxygreen process, a treatment by ozone, in a closed sequential batch reactor. Leucotriene B4 (LTB 4) was induced by germination, but ozone treatment did not increase this effect. Extract obtained from these wheat batches was applied on human epithelial bronchial cells. Wheat extract from nongerminated wheat did not induce any DNA adduct. More the wheat germination gets underway, more DNA adducts are observed. In contrast, germination did not affect the cell viability. Ozonization of wheat exemplified genotoxic effects only if the wheat was germinated. The implication of hydroxamic acids is discussed. In conclusion, ozonization of wheat, of high milling quality, does not pose any problem.