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Bioactive compounds in fish and shellfish hydrolysates.


Protein hydrolysates have been prepared from several fish by-product fractions, however, a significant immuno stimulating activity was obtained only with hydrolysates from shrimp (Pandalus brealis) waste. Shrimp waste hydrolysates were prepared by enzymatic hydrolysis. It has been shown that protein hydrolysates containing immuno stimulating agents can be produced by the application of a commercial protease at defined experimental conditions. The immuno stimulating activity was determined during in vitro studies with Atlantic salmon (Salmo salar) macrophages. Shrimp waste hydrolysate was prepared by hydrolysis for 2h at 40 degrees Celsius by the protease alcalase. The hydrolysate was fractionated by gel filtration and the immuno stimulating activity of each fraction was tested. It appeared, however, that the best results were obtained with the un-fractionated hydrolysate. The immunostimulating activity was determined as improved superoxide anion production in salmon macrophage after incubation with low concentrations (10-100 umol/ml) of shrimp waste hydrolysates for 2-6 days. The stimulation was comparable with, and sometimes higher than what was obtained with lipo-polysaccharides (LPS) from bacterial cell membranes, which are known to be potent immuno stimulants. The practical implication of this result is that application of shrimp waste hydrolysate in fish feed may improve disease resistance.
The properties of fish hydrolysates as microbial peptones were explored on Saccharomyces cerevisiae, Lactobacillus casei and Escherichia coli strains. Performances of peptones for production of cell biomass exhibited large differences, depending on the strain tested. A correlation between the peptone hydrolysis rate and the biomass production was observed for E. coli and L. casei. The high vitamin and mineral content of the peptones tested allowed high performances for hard-to grow microbial cells. Enumeration of Vibrio parahaemolyticus from seafood has become important according to the recommendations of the International Commission of Microbiology Specifications for Foods (ICMSF). The main conclusion which can be withdrawn from the results obtained is that commercial peptone can be replaced by fish protein hydrolysate in order to quantify Vibrio parahaemolyticus by the most probable number technique (following the FDA method). The main objective was to improve the overall knowledge on the suitability of using fish hydrolysates as microbial substrates. We showed that differences in peptones performances were mainly due to three factors: -Hydrolysis degree. -Mineral contents (e.g. oligoelements). -Vitamins contents. We have tested 8 fish peptones differing with regards of fish species, production process and consequently of chemical composition. Some of these fish peptones performed better than the reference one from casein (reduced lag phase, increased growth rate, enhanced yield). This was especially noticed on hard-to-growth microorganisms, i.e. Lactobacillus casei
A major problem with the production of high value products from fisheries waste arises from the unavoidable variability of waste material from capture fisheries. To minimise the impact of this variability on the reproducibility of product formation, we have used three strategies. 1. endogenous proteases and peptidases have been heat-inactivated prior to addition of controlled amounts of exogenous enzymes. This step decreases product variability due to the presence of endogenous enzyme (variable in nature and quantity). 2. controlled hydrolysis has been carried out using mixtures of commercial proteases and peptidases to increase waste protein digestibility and maximise the formation of low molecular mass products. 3. where larger molecular mass products are required, control over the feedstock waste is needed. This can be achieved by the use of waste from farmed fish rather than capture fisheries. Using capture fisheries waste, the potential applications of hydrolysates will be those requiring only small peptides or free amino-acids such as microbial and/or cell culture media, flavour enhancers (organoleptics) feeding stimulants (for aquaculture species), dietary supplements (to enhance foods with amino acid deficiencies). Using aquaculture species wastes, the potential applications will be those requiring larger peptides with biological activities such as immuno-stimulants, enzyme inhibitors, peptides hormones. The result is a process using enzyme biotechnology to upgrade low value fisheries wastes to high value products. The process can be applied to products of interest to aquaculture, food science, microbiology and cell biology. Given concerns about the possible consequences of using cell culture media based on animal products (e.g. calf serum). culture media based on fisheries waste may be seen to have considerable potential. In addition, using natural immuno-stimulants to replace antibiotics and other medicines in aquaculture may be more attractive to farmers and consumers as well as decreasing the levels of undesirable residues in marketed aquaculture products. The potential use of products in aquaculture nutrition as replacements for expensive fish meal may allow the development of lower-cost and sustainable diets based largely on plant proteins. The use of enzymes to reproduce hydrolysates from fish wastes has a long history. little work has been carried out using mixed enzyme protarations to enhance waste digestibility and improve products reproducibility. Most immuno-stimulants are base on microbial polysaccharides or chitinous wastes from shellfish. There is relatively little work published on peptide immunostimulants. Our results are at least comparable with the state of the art in the field. The process relies only on available technologies in the biotechnology/food industries. It does not require the development of new technologies for exploitation.

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