Yeasts are ubiquitous in their distribution and populations mainly depend on the
type and concentration of organic materials. The distribution of species, as well as
their numbers and metabolic characteristics were found to be governed by existing
environmental conditions. Marine yeasts were first discovered from the Atlantic
Ocean and following this discovery, yeasts were isolated from different sources, viz.
seawater, marine deposits, seaweeds, fish, marine mammals and sea birds. Nearshore
environments are usually inhabited by tens to thousands of cells per litre of
water, whereas low organic surface to deep-sea oceanic regions contain 10 or fewer
cells/litre. Aerobic forms are found more in clean waters and fermentative forms in
polluted waters. Yeasts are more abundant in silty muds than in sandy sediments.
The isolation frequency of yeasts fell as the depth of the sampling site is increased.
Major genera isolated in this study were Candida, Cryptococcus, Debaryomyces and
Rhodotorula. For biomass estimation ergosterol method was used. Classification and
identification of yeasts were performed using different criteria, i.e. morphology, sexual
reproduction and physiological/biochemical characteristics. Fatty acid profiling or
molecular sequencing of the IGS and ITS regions and 28S gene rDNA ensured
accurate identification.
Rosamma, Philip; Preetha, R; Jayaprakash, N S; Bright Singh, I S(The Society for Applied Microbiology, 2007)
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Abstract:
Aim: To develop a new medium for enhanced production of biomass of an
aquaculture probiotic Pseudomonas MCCB 103 and its antagonistic phenazine
compound, pyocyanin.
Methods and Results: Carbon and nitrogen sources and growth factors, such as
amino acids and vitamins, were screened initially in a mineral medium for the
biomass and antagonistic compound of Pseudomonas MCCB 103. The selected
ingredients were further optimized using a full-factorial central composite
design of the response surface methodology. The medium optimized as per the
model for biomass contained mannitol (20 g l)1), glycerol (20 g l)1), sodium
chloride (5 g l)1), urea (3Æ3 g l)1) and mineral salts solution (20 ml l)1), and
the one optimized for the antagonistic compound contained mannitol (2 g l)1),
glycerol (20 g l)1), sodium chloride (5Æ1 g l)1), urea (3Æ6 g l)1) and mineral
salts solution (20 ml l)1). Subsequently, the model was validated experimentally
with a biomass increase by 19% and fivefold increase of the antagonistic
compound.
Conclusion: Significant increase in the biomass and antagonistic compound
production could be obtained in the new media.
Significance and Impact of the Study: Media formulation and optimization are
the primary steps involved in bioprocess technology, an attempt not made so
far in the production of aquaculture probiotics.
Marine yeasts (33 strains) were isolated from the
coastal and offshore waters off Cochin. The isolates
were identified and then characterized for the utilization
of starch, gelatin, lipid, cellulose, urea, pectin,
lignin, chitin and prawn-shell waste. Most of the
isolates were Candida species. Based on the
biochemical characterization, four potential strains
were selected and their optimum pH and NaCI
concentration for growth were determined. These
strains were then inoculated into prawn-shell waste
and SCP (single cell protein) generation was noted in
terms of the increase in protein content of the final
product.