Highlight Research New method to synthesis nano chitosan from Vannamei shrimp with high Deacetylation Degree Nano chitosan from Vannamei shrimp can adsorb heavy metal Fe up to 81.35% Shrimp shells as an alternative adsorbents for Fe Abstract Shrimp cultivation produces shrimp wastes in several forms, including shells from the molting process. Shrimp shell waste can be used as a source of nano chitosan. Many researches have used nano chitosan for various applications, one of which is to adsorb heavy metal pollution. This present study aimed to extract chitosan from shrimp shells and investigate the ability of nano chitosan to adsorb Fe metal. The research began by isolating chitin and chitosan from shrimp shells through deproteinization, demineralization, and deacetylation. The obtained chitosan was afterward characterized using Fourier Transform Infrared (FTIR). Furthermore, the glassy ionic method was used to synthesize nano chitosan. Nano chitosan was characterized using a scanning electron microscope (SEM), and the Fe metal adsorption ability was measured using Atomic Absorption Spectroscopy (AAS). The FTIR results showed that the synthesized shrimp shells had successfully formed chitin compounds with the appearance of the C-O-C functional group, while the chitosan compounds with the appearance of O-H and N-H groups. The SEM characterization showed that nano chitosan with a size of 173.71 nm was successfully formed with identical morphology in the form of a flat (spherical), elongated, and irregular position. The nano chitosan was able to absorb Fe solution up to 81.35%. Therefore, nano chitosan from the shrimp shells is suitable as an adsorbent of heavy metal Fe.

Yersiniosis of cultured Atlantic salmon is a recurrent fish health management challenge in many continents. The causative organism, Yersinia ruckeri, can reside latently in the gut and lead to acute infection and disease during hatchery and sea-transfer stages. One potential prevention approach is the administration of probiotic bacteria to suppress gut colonization of Y. ruckeri. Our study aimed to isolate and identify anti-Yersinia activity among lactic acid bacteria (LAB) isolated from the gastrointestinal tract (GIT) of aquatic animals. Of the 186 aquatic GIT isolates examined, three strains showed diffusible antimicrobial activity towards Y. ruckeri O1b. Analysis of 16 s rRNA gene sequences indicated the three bacterial strains were Enterococci, related to Enterococcus sp. (99%), Enterococcus thailandicus (99%), and Enterococcus durans (99%). Anti-Yersinia activity was maintained at neutral pH (similar to 6.5-7.0), and in-vitro environmental tolerance assays showed the three strains could withstand simulated salmonids gastrointestinal tract conditions of: low pH (3.4) and 3% bile salt content. All three Enterococci strains showed higher adhesion to the intestinal mucus of Atlantic salmon than Y. ruckeri O1b (E. durans 24%, E. enterococcus sp. 25% and E. thailandicus 98%, compared to Y. ruckeri O1b 5%). However, only Enterococcus sp. and E. thailandicus were able to grow in the salmon intestinal mucus broth while E. durans showed no growth. Anti-Yersinia activity was completely inactivated by proteinase-K treatment, suggesting that the active compound/s are proteinaceous and may be bacteriocin-like inhibitory substances (BLIS). Our data indicate that Enterococcus sp. MA176 and E. thailandicus MA122 are potential probionts for the prevention of yersiniosis in salmonids. Further in-vivo studies are required to determine whether these bacteria reduce the incidence of yersiniosis in Atlantic salmon.