QUALITY VARIATION IN CHITOSAN EXTRACTED FROM Macrobrachium rosenbergii (de Man, 1879) CULTURED IN  TROPHICALLY DIFFERENT RESERVOIRS IN SRI LANKA 

Chitosan, a derivative of chitin, is found in the exuviae of crustaceans, including  Macrobrachium rosenbergii, which is considered an important commodity in the culture-based  fisheries in Sri Lanka. The present study evaluates the influence of the trophic state of selected dry zone perennial reservoirs of Sri Lanka (n=25) on the quality and quantity of the chitosan isolated from M. rosenbergii exuviae. Carlson’s Trophic State Index (TSI) was calculated based on the chlorophyll-a content in the reservoirs. Morphometric characteristics, length-weight relationship, condition factor, food composition in the stomach, and fecundity of M. rosenbergii samples collected from trophically different reservoirs were estimated. Discarding inedible exoskeletons of M. rosenbergii are used to extract chitosan through deacetylation process following the pre-conditioning, de mineralization, de-proteinization, and de acetylation (40% NaOH, 10% W/V at ambient temperature for 12 hours) steps. The functional property of extracted chitosan was characterized by Fourier Transforms Infra-Red spectroscopy (FT-IR), and the physicochemical properties of chitosan, i.e., moisture, ash, water and fat binding capacity, solubility, nitrogen, and degree of deacetylation were evaluated concerning the  different trophic statuses of reservoirs. TSI computed for the selected reservoirs indicated = that most of the (56%, n=14) reservoirs were mesotrophic while the rest (44%, n=11) were eutrophic. The highest biometric characteristics of M. rosenbergii are visible from the eutrophic reservoirs over the mesotrophic reservoirs. The present findings elucidate that GFP shows positive allometric growth (b=3.7189 in males and 3.1350 in females) and, higher fecundity  (131.49±69.09) in eutrophic reservoirs than mesotrophic reservoirs. Significant difference  (p