Studies on Lactic Acid Bacteria from Tropical Fish and Shellfish

In this study, an attempt has been made to gather enough information regarding lactic acid bacteria from fish and shellfish of tropical regions. The occurrence and distribution of lactic acid bacteria in fresh and frozen marine fish and shellfish, farmed fish and shellfish, cured and pickled fish and shellfish have been investigated. Lactic Acid Bacteria (LAB) have for centuries been responsible for the fermentative preservation of many foods. They are used to retard spoilage and preserve foods through natural fermentations. They have found commercial applications as starter cultures in the dairy, baking, meat, fish, and vegetable and alcoholic beverage industries. They are industrially important organisms recognized for their fermentative ability as well as their nutritional benefits. These organisms produce various compounds such as organic acids, diacetyl, hydrogen peroxide and bacteriocins or bactericidal proteins during lactic fermentations.Biopreservation of foods using bacteriocin producing LAB cultures is becoming widely used. The antimicrobial effect of bacteriocins and other compounds produced during fermentation of carbohydrates are well known to inhibit the growth of certain food spoiling bacteria as well as a limited group of food poisoning and pathogenic bacteria LAB like Lactobacillus plantarum are widely used as starter cultures for the Production of fish ensilage. The present study is the first quantitative and qualitative study on the occurrence and distribution of lactic acid bacteria in fresh and frozen fish and prawn. It is concluded that Lactobacillus plantaruni was the predominant lactobacillus species in fresh and frozen fish and shellfish. The ability of selected Lactobacillus cultures to grow at low temperatures, high salt content, produce bacteriocins, rapidly ferment sugars and decrease the pH make them potential candidates for biopreservation of fish and shellfish.

Enzyme reactions as index of freshness of Fish and Shellfish

An attempt has been made in this study to screen some fish muscle enzymes to assess their potential worth in testing the degree of freshness of fish. A problem with routine enzyme activity determinations is the complexity of the method of enzyme assay. Hence, in the present study as far as possible simple assay techniques were adopted. Several species were screened to assess the possibility of employing this procedure on a large scale. It is hoped that findings of this study will lead to the development of meaningful criteria in testing the freshness of fish. This thesis has been divided into five chapters

Studies on finfish and shellfish diseases

In the present study, fifteen typee of diseases occurring in twenty one species of finfishes end shellfishes are documented and the causes studied. All these are being reported from India for the first time which adds considerably to our existinq knowledge on the subject.In fact, the candidate's studies embodied in this Thesis has also an applied significance aimed at the proper management_of finfish and shellfish aquaculture systems in this country.The thesis is presented in seven main chapters.

Standardization of Optimum Conditions for the Production of Glucosamine Hydrochiloride from Chitin

The study entitled standardization of optimum conditions for the production of glucosamine hydrochloride from chitin. Shellfish processing industries around the world turn out a significant quantity of head and shell as industrial waste. The waste must be removed immediately to prevent the contamination to the processing environment. The technique that are available for their disposal include ocean dumping, incineration or disposal of landfill sites. In this thesis the techniques and methods are used to process glucosamine hydrochloride from crustacean processing waste. Chitin is a nitrogenous polysaccharide, which is white, hard, inelastic, found in outer skeleton of insects, crabs, shrimp and lobsters and in the internal structures of other invertebrates. Glucosamine can be considered as a nutraceutical product by virtue of its properties. It is important for healthy skin, and plays a major role in the healing of surgical incisions and skin wounds. Deproteinisation of shrimp shell had significant effect on quality of chitin. Demineralization is also influences chitin quality. Solvents used for glucosamine hydrochloride affects the final yield and purity.

STUDIES ON TAXONOMY, DISTRIBUTION, ECOLOGY AND REPRODUCTIVE POTENTIAL OF ROTIFERS FROM SELECTED CENTRES IN COCHIN BACKWATER SYSTEM, KERALA

The studies were conducted in nine stations with varying ecological characteristics along Cochin backwaters and adjoining canals. Many workers opined that the distribution of rotifers is cosmopolitan. The significance of rotifers as first food for early larvae was indicated by Fujita. Aquaculture is a fast growing field in fisheries sector and it is gaining more importance as the fish landings and supply are getting irregular. A consistent supply of fish/shellfish can only be achieved through aquaculture. The success of any culture activity depends on the timely production of seeds of finfishes/shellfishes. The availability of wild seed is seasonal and erratic. So, a dependable source of seed of fishes and shellfishes is possible only through large scale production in hatchery. A successful seed production activity depends on the availability of a variety of suitable live feed organisms in sufficient quantities at the proper time for use in the larval stages. As the live feeds promote high growth rates, easy digestion, assimilation and the quality of not contaminating the culture water when compared to other artificial feeds, make the culture of live feed organisms the principal means of providing food for the larvae of finfishes and shellfishes. Rotifers are considered to be an excellent and indispensable food for larvae of many finfishes and crustaceans. It (1960) was the first to culture Brachionus plicatilis for feeding marine fish larvae, and now it is being extensively used as live feed in hatcheries all over the world. They are a group of microscopic organisms coming under the Phylum Rotifera which comprises of about 2000 species. Their slow swimming habits, ability to tolerate a wide range of salinities, parthenogenetic mode of reproduction and ability to get enriched easily, make rotifers an ideal live feed organism. The major factors such as temperature, salinity and food that influence the reproductive potential and thereby the population size of rotifer, Salinity is one of the most important aspect influencing the reproductive rate of rotifers. The feed type and feed concentration play a vital role in influencing the reproductive rate of rotifers. For culture of rotifers, the commonly used micro algae belong to Chlorella, Nannochloropsis, Isochrysis and Tetraselmis. While some studies have suggested that, algal diet has little effect on reproductive rates in 1979 while using the rotifer, Brachionus plicatilis as feed for the larvae of red sea bream, Pagrus major. It is generally accepted that rotifers play a pivotal role in the successful rearing of marine fish larvae.

Studies on the prevalence of algal blooms along Kerala coast, India

Algal blooms are naturally occurring phenomena in the aquatic environment. These blooms cause mass mortalities of wild and farmed fish and shellfish, human intoxications which sometimes result in death, alteration of marine trophic structure through adverse effects on larvae and other life history stages of commercially important species and death of marine animals. Occurrences of harmful algal blooms and associated mortality have been reported along the coastal waters of India since the early period of the last century. The present study was taken up to study the dynamics of major phytoplankton blooms, which occur along the Kerala coast. The results of quantitative and qualitative analysis of phytoplankton in the coastal waters of Vizhinjam and Chombala, their species diversity and community structure is presented and the major algal blooms recorded along the coast of Kerala during the study period is described and their occurrence is related to the hydrographic and meteorological variations. There is a clear evident from these works in the Indian region that the fishes avoid areas where these harmful algae bloom, either due to the toxicity or due to some irritant property of the chemicals secreted by the algae. Taxonomic diversity studies indicated a change in the community structure of commercial finfishes, crustaceans and molluscs due to the bloom of C.marina and funnel plots indicated the deviation in taxonomic distinctness during the bloom period from theoretical mean for the region.

lncidence of enterotoxigenic Staphylococcus aureus in relation to the microbial safety of seafood

A detailed study was made on the microbial quality, with special reference to food safety, of the fish and fishery products in the retail trade in Cochin and around. Also, farmed molluscan shellfishes like mussels and oysters were investigated for the microbial quality including the presence of pathogenic bacteria. Special stress has been given to monitor the incidence of coagulase positive as well as coagulase negative Staphylococcus in these products and their relative incidence have been recorded.In the next part, the investigation was centered mainly on toxigenic S.aureus. This is because among the Gram positive toxigenic bacteria, the Saureus with potential to produce thermostable enterotoxins are more relavent in food safety conceming seafoods in comparison with the Gram-negative pathogens like Salmonella and V.cholerae.The incidence, toxigenic potential and conditions of toxin production by S.aureus have been investigated in detail. An attempt has also been made to relate the toxigenisis with the presence of the concerned toxigenic genes in the genomes of S. aureus strains.

Chitinase production by.marine fungi

In this thesis an attempt is made to explore the potential of marine fungi for the production of chitinolytic enzymes and to recognize the ability to hydrolyse native chitin through submerged as well as solid substrate fermentation culture conditions, using wheat bran and shellfish processing waste such as ‘prawn waste’ as solid substrates. Attempt was made to isolate a potential chitinase producing fungus from marine environment and to develop an ideal bioprocess for the production ofchitolytic enzymes.Present study indicate scope for utilization of B. bassiana for industrial production of chitinase using prawn waste as solid substrate employing solid substrate fermentation.

Influence of collagen content on the texture andstorage quality of fish mince basedproducts

Objectives of the present study are to find out the proximate composition of 20 commercially important tropical fish species on the west coast of India. To determine the collagen content in these commercially important fish species and fractionation of collagen into acid soluble collagen (ASC) and hot water soluble (insoluble) collagen (ISC). To classify fishes according to its collagen content and To study the different storage characteristics in the mince based product—surimi, from different species of fishes. The researcher tries to find out a suitable collagen source to incorporate in surimi. and studies the different storage qualities in the mince based product, surimi at different levels of collagen in different species of fishes. The optimum collagen level to get desirable texture and storage quality for mince based product. The researcher aims to develop some products from surimi with desirable level of collagen. And compare the products prepared from surimi of lesser collagen content fish containing desirable level of collagen with surimi prepared with high collagen content fish without collagen. This study gains in importance as there is littleinformation on the collagen content of different species of fishes in India. So far no attempt was made to classify fishes according to its collagen content.

Investigations on Phaeocystis sp., A Harmful Bloom- Forming Alga Isolated from Cochin Estuary

Considering the importance of diversity of micro algae in our ecosystem and new invasion of many organisms, an attempt was made to monitor the Cochin estuary along the south west coast of India for the qualitative distribution of phytoplankton and to study the growth kinetics and allelopathic effect of the phaeocystis sp. Isolated from the cochin estuary. Phaeocystis blooms are common only in high latitude environments and they rarely occur in low latitude environments such as tropics and subtropics. As phaeocystis is grouped under harmful alga ,in the present study the factors causing the blooms formation in the ecosystem. The nutrient concentration of the water body along with other physiochemical parameters that includes temperature salinity and ph play an important role in triggering the bloom of phaeocystis .The phaeocystis harbor specific bacterial flora associated with it and they exert an important role in the growth ,haemolytic activity and the bloom phases of the alga. The harmful alga mainly depends on the production of alleopathic compounds for the establishment of bloom in the marine environments .These physiological properties of the phaecystis were considered for the study, along with the role of nutrients in the allelopathic and hemolytic activity

Nutritional Requirements Of The Fry Of Gold-Spot Mullet Liza Parsa (Hamilton)

Most tropical aquatic environments are naturally fertile and their natural fertility is renewed very rapidly. Natural food for many cultivable organisms can be grown to the maximum by proper management. However, enrichment of the environment can be done through rational fertilization. Still further increase in stocking rates, can yield increased crop if adequate feeding is done. Thus fish and shellfish nutrition is an important aspect of the multidisciplinary subject of aquaculture. The oldest and most classical studies in physiology have investigated the nutritional needs of the species of interest to aquaculture. The alimentary requirements for proteins, lipids, mineral salts and vitamins have been established for some temperate species. But, the nutritional requirements of only few tropical species have been studied. Before formulating a diet, a thorough knowledge of the nutrient requirement of the species is essential. It is against this background that the present area of investigation has been identified. "Nutritional requirements of the fry of gold-spot mullet Liza parsia" is a comprehensive attempt to quantify the nutritional factors that are essential for producing healthy fingerlings for stocking the farms. Aspects such as the protein and lipid requirements of the fry, the vitamin essentiality, nutritive evaluation of protein and lipid sources suitable for compounding diets were covered in this research project. The ultimate aim has been to evolve practical diets which could be applied in the nursery phase for juvenile production.

Studies on The Eco Biology of The Indian Pearl Oyster, Pinctada Fucata (Gould)

The present work aims to study induced maturation of the pearl oyster for induced spawning experiments. The work on larval development was done with a view to developing techniques for the artificial rearing of commercially important pearl oyster P fucata, and also to elucidate the principles and problems of tropical bivalve larvae in general for detailed investigations in the future. The present study is designed to probe into the details of the basic aspects of the biology related to the hatchery technology of Pinctada fucata and the understanding of the factors which influence induction of maturation, spawning, larval rearing and spat settlement. This would go a long way in the upgradation of hatchery technology of the Indian Pearl oyster Pinctada fucata fora commercial level seed production..

Molecular Approaches For Characterization And Determination Of Pathogenicity Of Vibrios With Special Reference To Vibrio Harveyi From Penaeus Monodon Larval Production Systems

The present study focuses on vibrios especially Vibrio harveyi isolated from shrimp (P. monodon) larval production systems from both east and west coasts during times of mortality. A comprehensive approach has been made to work out their systematics through numerical taxonomy and group them based on RAPD profiling and to segregate the virulent from non- virulent isolates based on the presence of virulent genes as well as their phenotypic expression. The information gathered has helped to develop a simple scheme of identification based on phenotypic characters and segregate the virulent from non virulent strains of V. harveyi.