Seaweed Hydrocolloid Production: An Update on Enzyme Assisted Extraction and Modification Technologies

Agar, alginate, and carrageenans are high-value seaweed hydrocolloids, which are used as gelation and thickening agents in different food, pharmaceutical, and biotechnological applications. The annual global production of these hydrocolloids has recently reached 100,000 tons with a gross market value just above US$ 1.1 billion. The techno-functional properties of the seaweed polysaccharides depend strictly on their unique structural make-up, notably degree and position of sulfation and presence of anhydro-bridges. Classical extraction techniques include hot alkali treatments, but recent research has shown promising results with enzymes. Current methods mainly involve use of commercially available enzyme mixtures developed for terrestrial plant material processing. Application of seaweed polysaccharide targeted enzymes allows for selective extraction at mild conditions as well as tailor-made modifications of the hydrocolloids to obtain specific functionalities. This review provides an update of the detailed structural features of κ-, ι-, λ-carrageenans, agars, and alginate, and a thorough discussion of enzyme assisted extraction and processing techniques for these hydrocolloids.     

A qualitative risk-based assessment of impacts on marine habitats and harvested species for a data deficient wild capture fishery

Fisheries management in most areas of the world is concerned with the effects of resource exploitation on the broad marine environment that includes all major ecological components. However, all fisheries lack some information about many of these components particularly marine habitats and non-target species. Such data deficiencies make it difficult to identify priorities for management action. Qualitative ecological risk assessment is one tool that can be used by management to prioritise and evaluate management strategies. This paper demonstrates the mechanics of a qualitative ecological risk assessment applied to a currently operating data deficient commercial fishery. In particular, we demonstrate how the method applies to two distinct ecological components – marine habitats and harvested species – and shows how it contributed to the formation of management responses. The method combines biological and ecological information about each component with knowledge on the operations of the fishery. Using pre-defined decision rules and criteria the available information is used in a rigorous, transparent and repeatable manner. The paper demonstrates that the method can be used generally to apply to all ecological components of a marine fishery where data is deficient.     

Pathogenesis of experimental bovine spongiform encephalopathy (BSE): estimation of tissue infectivity according to incubation period

This paper reports the results of tissue infectivity assays of bovine spongiform encephalopathy (BSE) agent in orally exposed cattle at stages during the incubation period. Estimations of the titre of infectivity in central nervous system (CNS), certain peripheral nerve ganglia and distal ileum tissue were made according to time post exposure from the relationship between incubation period and dose for RIII mice and C57bl mice using data from titrations of brain material from cases of BSE. The rate of increase of infectivity in the bovine CNS was then estimated, taking into account these tissue infectivity titres, the variability of the brain titre of clinical field cases of BSE, and the probability density of the expected number of months before clinical onset of each infected bovine. The doubling time for CNS was shown to equal 1.2 months. The titre in the thoracic dorsal root ganglia (DRG) was, on average, approximately 1 log units less than CNS, and cervical DRG approximately 0.5 log less than thoracic DRG. The pattern of increase of infectivity in the distal ileum is that of an initial increase up to 14-18 months post exposure, followed by a decrease, which is likely to be highly variable between animals. These results will be informative for future risk assessments of BSE, especially in relation to reviewing current control measures.     

Detection of specific antibody responses to vaccination in variable flying foxes (Pteropus hypomelanus)

Megachiropteran bats are biologically important both as endangered species and reservoirs for emerging human pathogens. Reliable detection of antibodies to specific pathogens in bats is thus epidemiologically critical. Eight variable flying foxes (Pteropus hypomelanus) were immunized with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA). Each bat received monthly inoculations for 2 months. Affinity-purified IgG was used for production of polyclonal and monoclonal anti-variable flying fox IgG antibodies. ELISA and western blot analysis were used to monitor immune responses and for assessment of polyclonal and monoclonal antibody species cross-reactivity. Protein G, polyclonal antibodies, and monoclonal antibodies detected specific anti-DNP antibody responses in immunized variable flying foxes, with protein G being the most sensitive, followed by monoclonal antibodies and then polyclonal antibodies. While the polyclonal antibody was found to cross-react well against IgG of all bat species tested, some non-specific background was observed. The monoclonal antibody was found to cross-react well against IgG of six other species in the genus Pteropus and to cross-react less strongly against IgG from Eidolon helvum or Phyllostomus hastatus. Protein G distinguished best between vaccinated and unvaccinated bats, and these results validate the use of protein G for detection of bat IgG. Monoclonal antibodies developed in this study recognized immunoglobulins from other members of the genus Pteropus well, and may be useful in applications where specific detection of Pteropus IgG is needed.     

The pathogenesis of experimental infections of Cryptosporidium muris (strain RN 66) in outbred nude mice.

Three groups of six-week-old nude outbred mice were orally infected with 400, 20,000 and 1,000,000 oocysts of Cryptosporidium muris (strain RN 66) per mouse, respectively. Oocysts were detected in the faeces from 10-18 days post-infection (p.i.) and continued to be shed in large numbers in all groups until the termination of the trial on day 89 p.i. Clinical signs were not observed in any of the infected mice and there was no significant effect on weight gain compared to uninfected controls. Histological examination revealed the presence of parasites confined to the glandular stomach. Parasitised gastric glands were dilated, hypertrophied and filled with numerous parasites. The glands had lost their normal cellular architecture and were lined with many undifferentiated cells. In some mice receiving the largest innoculum, the glandular mucosa was congested and the lamina propria infiltrated with eosinophils, polymorphs and lymphocytes.     

Wettability influences cell behavior on superhydrophobic surfaces with different topographies

Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavior on superhydrophobic surfaces is influenced by surface topography and polymer type. Biomimetic superhydrophobic rough surfaces of polystyrene and poly(L-lactic acid) with different micro/nanotopographies were obtained from smooth surfaces using a simple phase-separation based method. Total protein was quantified and showed a less adsorption of bovine serum albumin onto rough surfaces as compared to smooth surfaces of the same material. The mouse osteoblastic MC3T3-E1 cell line and primary bovine articular chondrocytes were used to study cell attachment and proliferation. Cells attached and proliferate better in the smooth surfaces. The superhydrophobic surfaces allowed cells to adhere but inhibited their proliferation. This study indicates that surface wettability, rather than polymer type or the topography of the superhydrophobic surfaces, is a critical factor in determining cell behavior.     

Sustainable Food Supply Chains

Abstract

The effects of washing on the chemical composition, gel-forming ability and color of Monterey sardine mince were investigated. Recoveries were 41.5, 46.3 and 52.1% for solids and 49.9, 52.7 and 59.9% for protein using washing ratios of 1:20, 1:15 and 1:10, respectively. No differences were detected among the washing treatments except for gel cohesiveness as measured by texture profile analysis. Large variations in muscle composition were observed at different months of harvesting which could preclude the effect of washing on the characteristics of the mince. Results showed that washed mince possesses an excellent gel-forming ability, suggesting that sardine could be used for surimi processing.     

Editor's Column

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