| :: News/Articles |
| Silver Medal for Nitrifying Bioreactor Technology under the Lockheed Martin India Innovation Growth Programme |
| The nitrifying bioreactor technology developed by the Centre won silver medal under The Lockheed Martin India Innovation growth Program. This is a two-year, nation-wide project, created to enhance the growth and development of India’s entrepreneurial economy. The program is wholly funded by Lockheed Martin Aeronautics Company, USA and was developed with the assistance of the IC2 Institute at the University of Texas, and FICCI. The overall goal of the program is to accelerate the launch of Indian early-stage technologies into the global marketplace. As an initial step towards the commercialization of the technology, our Industry partner Mr. Mohan Kandaswamy, Oriental Aquamarine Biotech India had applied the technology for India Innovation Growth Program. The FICCI along with the IC2 Institute, University of Texas at Austin has organized a three-day workshop on “Commercialization Strategies for Techno-Entrepreneurs” from 23rd to 25th April 2007 in FICCI, New Delhi. Top 30 applications, including the Nitrifying bioreactor Technology developed with DBT funding have been selected from 100 technologies during this workshop. A detailed Quicklook© technology commercialization strategy for the Nitrifying Bioreactor Technology was prepared by Mr. Jim Vance of the IC2 Institute, University of Texas at Austin before going to compete for the Lockheed Martin Innovation Medal. These 30 applicants met an international panel of prestigious technologists in July 2007 and competed for the Lockheed Martin Innovation medal. From the 30 applicants fourteen Indian entrepreneurs were awarded for their innovative technologies. Seven innovators won the Gold Medal and the others won the Silver. The Nitrifying Bioreactor Technology won the Silver Medal. The awards were distributed by Dr. T. Ramasami, Secretary, Department of Science and Technology at New Delhi on 18th July 2007. |
| NCAAH recognized as NACA Regional Resource Centre |
| National Centre for Aquatic Animal Health has been recognized as the seventh Regional Resource Centre (RRC) of the Network of Aquaculture Centers in Asia Pacific (NACA) with its Headquarters in Bangkok, Thailand. Focus of the RRC is Aquatic Animal Health. The other six Centres are located, three in China, one each in Australia, Bangkok and Singapore. Ours is the only Centre in India. |
| TRANSFER OF TECHNOLOGY |
| Cochin University of Science and Technology at its National Centre for Aquatic Animal Health developed/invented a TECHNOLOGY named BIOREACTORS FOR NITRIFYING WATER IN CLOSED SYSTEM HATCHERIES OF PENAEIDS AND NON-PENAEID PRAWNS through the implementation of two research projects funded by Department of Biotechnology (DBT), Government of India under the principal Investigatorship of Dr. I.S. Bright Singh, Reader in Microbiology & Coordinator of Centre and Co-Investigatorship of Dr. Rosamma Philip, Sr. Lecturer in Microbiology, Department of Marine Biology, Microbiology and Biochemistry, School of Marine Science, CUSAT having Dr. Cini Achuthan, Ms. Manju N.J. and Mr. V.J. Rejish Kumar as the Research Fellows. The technology has been patented. To make available the technology to aquaculture industry it is being transferred to M/S Oriental Aquamarine Biotech India Private Limited Coimbatore at cost of Rs. 15 lakhs. Besides on commercialization the University will be receiving a royalty of 5% for a period of 5 years. |
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| Significance of the technology is summarized as follows: |
| Shrimp industry globally has been suffering serious set backs in different forms one after the other. One among the impediments is the difficulty, which has been experienced by the industry in attaining stipulated quality in the production process in tune with the demand of International market. Quite invariably this quality upgradation has to be achieved only through natural means without the input of any synthetic compound, which may leave residue in the environment. Organic farming, a multi faceted technology to be evolved by harnessing the potentials of nature, is the sole answer to this dogma. In organic shrimp production process the prime requirement is none other than organically produced shrimp seed. To satisfy this requirement a novel Recirculation System for Organic Shrimp and Prawn Seed Production has been developed. The nitrifying bioreactor technology mentioned above formed the major component of the system, which facilitate conversion of the conventional open systems to closed ones with recirculation. Two categories of reactors have been developed such as In-Situ Stringed Bed Suspended Bioreactors (SBSBRs) and Ex – Situ Packed Bed Bioreactors (PBBRs). Principally the integration of the reactors is at three locations in a larval production system such as, 1. PBBRs in the reservoir system. 2. PBBRs at brood stock maturation system and 3. SBSBRs at the larval rearing |
| The transfer of technology was carried out on 28th June 2006 in the chamber of the Honorable Vice chancellor of Cochin University of Science and Technology Dr. P.K Abdul Azis by handing over the technology transfer agreement to Mr. Mohan Kandaswamy, Managing Director. Oriental Aquamarine Biotech India (P) Ltd. The function was attended by Dr. I.S. Bright Singh, the Principal Investigator of the project & Co - ordinator of National Centre for Aquatic Animal Health, Dr. N.D. Inasu, Pro-Vice Chancellor, Dr. A. Ramachandran, Registrar, Sri Sebastain Ouseph, Finance officer, Dr. M. Rajan; planning and Development Officer and Dr. K.T. Damodaran, Director School of Marine Sciences. |
| CFDDM announces the release of the first book on |
| Aquaculture Medicine |
| ISBN 81-900724-1-2 ; Hard Bound |
| The book is a compilation of the papers presented by eminent scientists during the two workshops on ‘Aquaculture Medicine’ and ‘Aquaculture Drugs’ conducted by the Centre in 2001 and 2002 respectively. The book introduces the subject as a discipline to be practiced at field level in a scientific and professional manner. The 336-page book gives an excellent and comprehensive overview of 11 disciplines that encompass the subject Aquaculture Medicine and would be a treasure for all stakeholders of aquaculture including students. Click here for details and order form |
Probiotics as Biocontrol Agents in Aquaculture |
S. Somnath Pai |
| Aquaculture is one of the fastest growing food producing
sectors of the world. According to FAO it is growing at approximately
at 10% per annum and is looked upon as a major supplier of fish protein
to the human populace in future since production from capture fisheries
has peaked and growth virtually non existent. But aquaculture is beset
with multitudes of problems and the single most limiting factor is
disease. In the beginning diseases could be controlled using chemotherapeutants,
disinfectants and antibiotics, but when culture intensified and use
of these compounds rampant and unscientific, the disease causing organisms
became more resistant and thereby recalcitrant so much so that production
came to a virtual standstill in many culture areas. In addition to
resistance problems, use of chemicals and antibiotics in aquaculture
impaired the growth of cultured species, posed a threat to human health
and the environment at large by way of residual effects. Driven by
greater consumer awareness in consuming countries, legislations have
been brought into effect which effectively rejects any produce carrying
such residues. It is in the backdrop of these problems that researchers
and aquaculture managers began to look at alternative therapeutics
and look at the aquaculture system in a more environmental perspective
than that of a production system and the buzzword now is organic aquaculture.
The aim now is to manage a culture using probiotics, immunostimulants,
vaccines and the aquatic environment at large without at any stage
resorting to inorganic drugs and chemicals. In this article we limit
ourselves to probiotics and not the others. What are probiotics? Many have attempted to define probiotics but the definition proposed by Fuller (1989) came to be widely accepted. He defined probiotics as “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal balance”. This definition could not be accepted for aquaculture probiotics since the definition does not encompass the role played by environment and in aquatic animals intestinal microflora is believed to be transient and colonization and community structure is yet to be established. Verschuere et.al. (2000) argued that in aquatic systems, probiotic bacteria may be active on the gills, skin or ambient environment of the host and bacteria may be ingested with water or feed. Moreover, eggs of aquatic animals are axenic and ambient bacteria play a major role in the development of the eggs to larvae and growth of larvae to adulthood. Considering these factors they proposed a definition, “a probiotic is defined as a live microbial adjunct which has a beneficial effect on the host by modifying the host-associated or ambient microbial community, by ensuring improved use of the feed or enhancing its nutritional value, by enhancing the host response towards disease, or by improving the quality of its ambient environment”. This is a more holistic definition and most appropriately defines probiotics for aquaculture. Microbial communities are affected by a number of factors in aquaculture systems during pond preparation and the culture period. Disinfection, cleaning and discontinuous culture cause nutrient imbalances which affect population structure of microbial communities and thereby productivity. Microorganisms play an integral role in the cycling of nutrients and during the culture when there is a heavy build up of organic matter mainly by way of fecal matter and uneaten feed. If this organic matter is not degraded and recycled quickly then it will lead to build up of toxic ammonia, lower dissolved oxygen levels and possible proliferation of vibrios and these factors can adversely affect the health of the cultured species. The presence of good probiotic bacteria with rapid degradative potential can ameliorate this situation and convert the wastes to forms which can then be utilized by the phytoplankton resulting in recycling. It is in this light that the Centre has come out with the probiotic formulation “Detrodigest”, a consortium of indigenous bacteria with excellent hydrolytic properties. This formulation has now been available to farmers in Kerala, Tamil Nadu, Andhra Pradesh and Maharashtra where extremely good results have been reported. |
| A question asked is whether microbial communities
can be manipulated in an aquaculture system. From the experiments
of Verschuere et.al., 1999, it is evident that emerging microbial
communities can be manipulated to our desire. In their experiments,
preemptive colonization of Artemia cultures with selected bacterial
strains improved the zootechnical performance of the juveniles and
the introduced bacteria had a drastic influence on the overall microbial
community of the system. Rico-Mora et.al., 1998 were able to prevent
the establishment of Vibrio alginolyticus in diatom (Skeletonema costatum)
cultures using a bacterial strain (SK-05) selected for its active
growth in organic-poor substrates. While these studies indicate that
bacterial establishment may be manipulated in emerging communities
but no experimental data is available to indicate the same is possible
in established communities. Theoretically it seems this would be difficult
for many reasons; i) it would take some time for the introduced organism
to adapt to the environmental conditions in the system, ii) there
is already an established community which will be in a position to
adapt faster to changing nutritional status of the system. In our
observations with “Detrodigest” applications in shrimp
culture ponds, we found it does not establish in the system even though
applied at high cell densities. The effect shown by the probiotic
may be due to the enzymes it produced during the brewing process and
not by its growth in the system.
A wide range of modes of action of probiotics have been recorded and a single candidate is likely to have one or more modes of action but not all. Production of inhibitory compounds by bacteria against other bacteria is long recorded characteristic. The compounds produced may be an antibiotic, bacteriocins, siderophores, lysozymes, proteases and/ or hydrogen peroxide. Many bacteria like Pseudomonas sp., Alteromonas sp., Bifidobacteria sp., lactic acid bacteria, actinomycetes etc., are known to produce inhibitory compounds against other bacteria. Literature is replete with microorganisms producing inhibitory compounds against other bacteria. All the studies have recorded inhibition of pathogens by candidate probiotics by production of inhibitory compounds under in vitro conditions. Inhibition of pathogens by probiotic bacteria by producing inhibitory compounds under in vivo conditions remains to be proved experimentally. Nevertheless, organisms continue to be selected as putative probionts using this as a primary criterion. Other modes of action proposed are competition for chemicals/ energy, competition for adhesion sites, enhancement of immune response and improvement of water quality. Competition for chemicals/ energy and adhesion sites is well recorded again under in vitro conditions but remains to be proved in vivo, although may be possible. Bacteria do adhere to the mucus layer on skin, gills and intestine in fish and shellfish, but what is in doubt is the duration of adhesion particularly in the intestine. Improvement of water quality by nitrification using nitrifying bacteria of published evidence is also available. But the role of other bacteria like Bacillus, Pseudomonas, Enterobacter, Cellulomonas and Rhodopseudomonas is little studied in this regard. |
| So how does one select a probiotic for application
in aquaculture? Verschuere et.al., 2000 in their review have proposed
a scheme following which one starts with the acquisition of bacterial
strains using which one has to then do some small scale in vivo tests
and thorough in vitro screening. This is followed by assessing the
pathogenicity of the selected candidate probiotics. Following pilot
scale trials under field conditions, pathogenicity at other trophic
levels must be studied. If it fails at any level here the culture
must be rejected as a probiotic and fresh cultures must be screened.
Vine et.al. (2004a,b) selected prospective probiotics for aquaculture
based on in vitro antagonism and growth characteristics in intestine
coupled with the ability of the bacteria to out-compete pathogens
for adhesion sites in intestinal mucus. If they are able to demonstrate
the beneficial effect of thus selected bacteria in improving fish
health under in vivo conditions then this approach could be used by
others in future. But as mentioned earlier such competition for adhesion
sites is yet to be demonstrated in vivo.
In conclusion, probiotics hold enormous potential to make aquaculture
sustainable and productive. It is estimated that our knowledge of
microbial diversity is yet miniscule when compared to overall diversity
available in the various environments on earth. As this knowledge
increases, the range of bacteria as probiotics will also increase.
And as our understanding of the microbial interactions particularly
in aquatic environments also increases, we can devise novel methods
of management of aquaculture systems more holistically. |
| Further Reading
1. Fuller, R., 1989. A review: probiotics in man and animals. J.
Applied Bacteriology, 66:365-378. |
| Microencapsulation as a Technique for Drug Targeting |
| A. Anas Senior Research Fellow CFDDM, CUSAT, Cochin 682016 Phone/Fax : 91 484 2381120 e- mail: anasabdulaziz@cusat.ac.in |
| Introduction Microencapsulation is a process in which very thin inert coatings of natural or synthetic polymeric materials are deposited around micro sized particles of solids or droplets of liquids. Products thus formed are known as microcapsules. Of late, there has been a widespread interest in this field and it has played a significant role in a variety of industries like pharmaceutical, cosmetic, food, agricultural, plastic, paper, photographic printing, paint, adhesive, and computer industries. The encapsulated capsules range in size from one micron (one-thousandth of a millimeter) to seven millimeters and release their contents at a later time by means appropriate to the application. Microencapsulation science evolved from polymer chemistry and was developed in response to an identified need for controlled material (active ingredient) inside a capsule wall, creating a tiny "bubble." The objective of microencapsulation is to contain the active ingredient inside the capsule wall for a specified time or in a specified environment. Modification in the composition of the capsule wall and the microencapsulation process can determine how, when or where the active ingredient inside the capsule is released. The first reference describing a microencapsulation process (preparation of gelatin microspheres by coacervation) dates back to 1931. However, it was only two decades later when this approach was applied to the microencapsulation of drugs. These microcapsules were initially designed to mask the taste and protect drugs from gastric fluids but were found suitable for sustained release of drugs. Many of these formulations are currently available in the market. These microencapsules, intended for oral administration, are composed of non biodegradable polymers from which the drug is frequently released by diffusion. These microspheres are not, however, adequate for the controlled release of peptides and proteins, since macromolecules cannot diffuse through polymers. It was only in the eighties when several investigators realized that in order to achieve controlled release of a macromolecule, a biodegradable polymer is required. A polymer, which erodes over a period of time when, exposed to biological fluids thus releasing the encapsulated molecules. Even vaccines could be microencapsulated to release only at a particular site. The feeds/ drugs used in aquaculture have to be microencapsulated due to the following reasons. 1. Since aquaculture feeds/drugs are applied in water, there is every possibility of loosing the ingredients without giving the desired effect. 2. Leaching of high protein ingredients may lead to water pollution and create unfavourable conditions for animal growth. 3. Many drugs like vitamins must be protected from photooxidation. 4. Effect controlled release of ingredients. |
| The art of microencapsulation consists of three steps 1. Design of wall material, 2. Selection of encapsulation method and 3. Design of release mechanism. |
| 1. Design of wall material.
A variety of coating materials are available to
produce microcapsules like gum arabic, carageenan, starch, caboxymethyl
cellulose, paraffin, silicates, albumin, gelatin etc. In most microcapsules,
the shell materials are usually organic polymers however, waxes
and fats have also been used, particularly in food and drug applications
where the shell must meet food and drug administration specifications. |
| 2. Selection of Encapsulation
Method. Numerous encapsulation processes have
been developed during the past several years. These include coacervation,
interfacial polymerization, spray drying, air suspension, centrifugal
extrusion and rotational suspension separation. The broad range
of capability available through these processes is important because,
according to Baken and Anderson (1970), no single encapsulation
process is adaptable to all core material conditions. |
| 2.1 Complex coacervation
This method is based on the ability of cationic and anionic water-soluble polymers to interact in water to form a liquid, polymer rich phase called a complex coacervate. Gelatin is the normal cationic polymer used. A variety of natural and synthetic anionic water soluble polymers interact with gelatin to form a complex coacervate suitable for encapsulation (Curt Thies 1996). When the complex coacervate forms, it is in equilibrium with a dilute solution called the supernatant. In this two-phase system, the supernatant acts as the continuous phase, whilst the complex coacervate acts as the dispersed phase. If a water insoluble core material is dispersed in the system and the complex coacervate wets this core material, each droplet or particle of dispersed core material is spontaneously coated with a thin film of coacervate. When this liquid film solidifies capsules are formed. This is the most widely used method of encapsulation in aquaculture. Yufera et.al. (2002) encapsulated the free amino acids by this method. They dispersed the dietary material in a basic pH buffered tris-HCl aqueous solution. Two parts of this solution were emulsified in five parts of soy lecithin and cyclohexane solutions. The crosslinking agent trimesoyl chloride, dissolved in diethyl ether, was then added to the emulsion. After the microcapsules formed were allowed to settle the cyclohexane lecithin solution decanted. Microcapsules were washed with cyclohexane and dispersed in a gelatin solution while stirring. Distilled water at a temperature approximately 38°C was added while stirring. The capsules were then repeatedly washed with fresh water, followed by a buffered saline solution (pH 8) to remove the debris. Langdon and Waldock (1981) encapsulated dietary lipids by complex coacervation using gelatin acacia as wall material which was fed to the juvenile C. gigas in combination with algal foods. |
| 2.2 Interfacial Polymerization
The unique feature of this technology is the
capsule shell is formed at or on the surface of a droplet or particle
by polymerization of reactive monomers. This approach to encapsulation
has evolved into a versatile technology able to encapsulate a wide
range of core materials, including aqueous solutions, water immiscible
liquids and solids. The wall of the nylon protein capsule is prepared
by interfacial polymerisation and is made up of protein cross linked
with 6,10 nylon (Chang et.al.,1996). The use of nylon–protein
walled microcapsules for delivering nutrition to aquatic filter
feeders was first described by Jones et.al (1974) who cultured Artemia
on a non-defined encapsulated diet. Jones et.al. (1976, 1979 a,b)
showed that it was possible to feed other crustacean species on
nylon–protein encapsulated diets and study some of their nutritional
requirements. They succeeded in rearing larvae of the prawn P. japonicus
from zoea to the post larval stage on a nylon–protein encapsulated
diet of chicken egg and powdered short necked clam, Tappes philippinarum. |
| 2.3 Spray Drying
It is the most commonly used method in the food industry. The process
is economical and flexible using equipment that is readily available
and produces good quality particles. The process is conducted in
a spray dryer, and involves three major steps (Judie, 1998) including
preparation of dispersion, or emulsion to be processed, homogenization
of the dispersion and atomization of the mass into the drying chamber. |
| The material to be atomized is prepared by dispersing it into a solution of the coating material with which it is immiscible. The coating is generally food grade hydrocolloids such as gelatin, vegetable gum, modified starch, dextrin or non gelling protein (Balassa and Fanger, 1971). Following addition of an emulsifier, the dispersion is homogenized to give an oil–in water type of emulsion, then atomized in a heated air stream supplied to the drying chamber (Sparks, 1981). As the atomized particle falls through the gaseous medium, they assume a spherical shape with the oil encased in the aqueous phase. This explains why most spray-dried particles are water-soluble. The rapid evaporation of water from the coating during its solidification keeps the core temperature below 1000C, despite the high temperatures used in the process (Branner, 1983) and the particle is exposed to heat only for few seconds at most (Balassa and Fanger, 1971). The main advantage of this method is its ability to handle many heat labile materials. Villamer and Langdon (1993) prepared capsules for delivering dietary components to larval shrimp (P. vannamaei). They developed a novel food particle type that retained low molecular weight, water soluble nutrients (glucose and vitamins) within lipid wall microcapsules embedded with dietary ingredients in particles of gelled alginate gelatin. |
| 2.4. Air suspension coating
It is also known as fluidized bed or spray coating
and is accomplished by suspending solid particles of core material
in an upward moving stream of air, which may be heated or cooled
(Baken and Anderson, 1970). The coating is atomized through nozzles
into a chamber and deposits as a thin layer on the surface of suspended
particles. The turbulence of the column of air is sufficient to
maintain a suspension of coated particle allowing them to tumble
and thereby become uniformly coated. |
| 2.5. Extrusion
It is a low temperature encapsulation method, involving forcing
a core material dispersed in a molten carbohydrate mass through
a series of disks into a bath of dehydrating liquid. On contacting
the liquid, the coating material, which forms the encapsulating
matrix, hardens to entrap the core material. The extruded filaments
are separated from the fluid bath, dried to mitigate hydroscopicity,
and sized. The extrusion process is particularly useful for heat
labile substances and has been used to encapsulate flavours, vitamin
C and colour. Using this technique Murano et.al (1997) encapsulated
formalin killed V. anguillarum and administered to rainbow trout
and concluded that oral vaccination of rainbow trout with alginate
encapsulated V. anguillarum may be used as booster vaccination in
combination with other vaccination. |
| 2.6. Centrifugal Extrusion
This is another encapsulation technique that has
been investigated and used by some vitamin manufacturers for the
encapsulation of vitamin A. The device consists of a concentric
feed tube through which coating material and core material are pumped
separately to the many nozzles mounted on the outer surface of the
device. Core materials flow through the center tube and the coating
material flows through the outer one. The entire device is attached
to a rotating shaft such that the head rotates around its vertical
axis. As the head rotates, the core material and coating material
are co extruded through the concentric orifices of the nozzles as
a fluid “rod” of core sheathed in coating material.
Centrifugal force impels the rod outward, causing it to break in
to tiny particles. By the action of surface tension, the coating
material envelops the core material, accomplishing encapsulation.
The capsules are collected on a moving bed of fine-grained starch,
which cushions their impact and absorbs unwanted coating moisture. |
| 2.7. Rotational Suspension
Separation The process involves suspending core particles in a pure, liquefied coating material, then pouring the suspension through a rotating disc apparatus under a condition that excess liquid between the core particles spreads into a film thinner than the core particle diameter. The excess liquid is then atomized into a very small particle, which is separated from the product and recycled. The core particle leaves the disc with residual liquid still around them, which forms the coating. Chilling or drying hardens the particles. Rotational suspension separation is a continuous high capacity process that takes seconds to minutes to coat core particles. The process can handle a wide variety of core materials and coating materials. This process handles each particle only once and, under most conditions, produces no uncoated particles. It has been successfully used to coat particles ranging from 30m to 2mm with a coating with a thickness ranging from 1- 200m. |
| 3. Design of Release Mechanism
A variety of release mechanism have been proposed
for microcapsules, but infact, the number that have actually been
achieved and of interest here are rather limited. These are as follows: |
| a. A comprehensive force breaks open the capsule by
mechanical measures b. Walls like gelatin rehydrate and release the core material on contact with water c. Wall material can be dissolved by acidic pH and enzymes present in the intestine of the animal |
| 3. Conclusion and Future
research The development and application of various
microencapsulation techniques has allowed researchers to formulate
and test satisfactory artificial diets for several species of aquatic
suspension feeders, such as prawn larvae, juvenile oyster and milk
fish larvae. The study by Murano et.al. (1997) indicates the possibilities
of microencapsulation technique for the effective administration
of vaccines and other drugs. |
| References
Baken,J.A., Anderson,J.L., 1970. Microencapsulation. In "The theory and practice of industrial pharmaccy" (eds.Lachman,L., Liberman,H.A., Kanig,J.L). Lee and Febiger, Philadelphia,Pa. P.384 Balassa, L.L., Fanger ,G.O., 1971. Microencapsulation in the food industry. CRC Reviews in food Technology.July.P245 Brenner,J., 1983. The essence of spray dried flavours: The state of the art. Per. Flav.April/May,P.40 Chang,T.M.S., Macintosh,F.C., Mason,F.G.,1996. Semipermeable aqueous
microcapsules. I. Preparation and properties. Canadian Journal of
Physiology and Pharmacology. 44,115-128 |
| Curt Thies.,1996. A survey of microencapsulation processes.
In "Microencapsulation methods and industrial applications"
(ed.Simon Benita).Marcel Dekker,Inc.N.Y. 17,1-21
Jones,D.A., Munford,,J.G., Cabhott,P.A., 1974. Microcapsules as artificial food particles for aquatic filter feeders. Nature. 247,233-235 Jones,D.A., Moller,T.H., Campbell,R.J., Munford,J.G., Gabbott,P.A.,1976. Studies on the design and acceptability of microencapsulated diets for marine particle feeders 1 .Crustacea. Proceedings of the 10th European symposium on Marine Biology. Ostend. 17-23 September,1975. 1,229-239 Jones, D.A., Kanazawa,A., Ono,K.1979a. Studies on the nutritional requirements of the larval stages of Penaeus japonicus using microencapsulated diets. Marine Biology.54,261- 267 Jones,D.A., Kanazawa,A., Rahman,S.A., 1979b. Studies on the presentation of artificial diets for rearing the larvae of Penaeus japonicus Bate. Aquaculture.17,33-43 Judie D.D., 1988. Microencapsulation and Encapsulated Ingredients. Food Technology.136-151. Langdon,C.J., Waldock,M.J.,1981. The effect of algal and artificial diets on the growth and fatty acid composition of Crassostrea gigas spat. Journal of the Mrine biological Association of the United Kingdom.61,421-448 Murano, E., Gatta ,P.P., Mazzolini, E., Giorgetti,G.,Bauce,G.,Perbellini,A., 1997. Oral immunization of rainbow trout Oncorhynchus mykiss against vibriosis with microencapsulated vaccine. International workshop on Bioencapsulation VI from fundamental to industrial applications, Barcelona,spain, august 30- September 1. Sparks,R.E., 1981. Microencapsulation. In "Encyclopedia of
Chemical technology". (Kirk Othmer ed.)3rd Ed.John Wiley and
sons,Inc.N.Y. 15,470. |
| Villamer,D.F., Langdon,C.J., 1993. Delivery of dietary
components to larval shrimp (Penaeus vannamei)by means of complex
microcapsules. Mar.Biol. 115,635 - 642
Yufera,M., Kolkovski,S., Fernandez - Diaz,C., Dabrowski,K.,2002.
Free amino acid leaching from a protein walled micro encapsulated
diet for fish larvae. Aquaculture. 214, 273 - 287 |