Sea-food processing wastes and underutilized species of fish are a potential source of functional and bioactive compounds. A large number of bioactive substances can be produced through enzyme-mediated hydrolysis. Suitable enzymes and the appropriate bioreactor system are needed to incubate the waste materials. Membrane separation is a useful technique to extract, concentrate, separate or fractionate the compounds. The use of membrane bioreactors to integrate a reaction vessel with a membrane separation unit is emerging as a beneficial method for producing bioactive materials such as peptides, chitooligosaccharides and polyunsaturated fatty acids from diverse seafood-related wastes. These bioactive compounds from membrane bioreactor technology show diverse biological activities such as antihypertensive, antimicrobial, antitumor, anticoagulant, antioxidant and radical scavenging properties.
About 78% of the total fish catch in both developing and developed countries is used as human food while the remainder is discharged as waste. Fish processing waste such as skin, bones and fins is about 7.3 million tons/year . There is considerable research that much of this waste, such as gelatin, collagen, fish oil and calcium, could have value as functional or bioactive materials. However, some of the traditional methods for extracting these materials use organic solvents and acids that may lower the functionality and bioactivity of the native materials. These chemicals could also be harmful since they may accumulate in the environment and cause problems to humans, animals and the environment. On the other hand, enzyme hydrolysis of fish waste has also produced many bioactive compounds. If combined with innovative processing methods such as membrane technology, there could be a new type of bioactive materials and we could avoid some of these limitations. The combination and integration of a bioreactor with membranes is known as a “membrane bioreactor” and is widely used in waste water treatment. Membrane bioreactors could also effectively produce compounds with desirable molecular weights (MW) such as chitooligosaccharides (COS) from chitin wastes, peptides from proteins and polyunsaturated fatty acids (PUFAs) from fish oil. Depending on the design of the membrane bioreactor, membranes can be selected and used to separate specific peptides from fish skin, scale gelatin and muscle.
Seafood processing wastes have great potential for the manufacture of bioactive substances. Even a few value-added compounds recovered from such wastes are economically more important than the target products themselves. However, their suitability as bioactive compounds and their pharmacological and nutraceutical values have not yet been properly evaluated and need to be studied more before considering them as nutraceuticals. Development of novel methods to produce and recover them is necessary. Membrane bioreactor technology can be used to separate and fractionate these bioactive compounds from marine wastes and will lead to the development of more profitable processes, thus giving rise to many great opportunities in the marine industry. The increased focus of membrane manufacturers on membrane bioreactor applications is likely to continue in the future and result in more cost-effective systems. Better membranes and more efficient modules are also likely additional future developments. Introduction of low-cost, low-energy bioreactor technology is necessary to increase its utilization. A better understanding of membrane fouling is needed and new strategies need to be developed to concentrate the bioactive materials (involving novel reactor designs), and to increase the immobilization of enzymes in the reactor (use of carrier materials)..