In aquaculture, Chitosan helps shrimp and crab healthy and strong with perfect molting.  Chitosan will enhance chitin formation which is a major component of aquaculture shell formation.  Naturally, shrimp and crab obtains chitin from small aquaculture such as krill and small shrimps.  However, in shrimp farming with restricted area and high population of shrimps, shrimps do not obtain enough chitin from nature.  Therefore, it is important to apply chitosan in form that shrimp can easily and immediately absorb to enhance chitin enough for shell and tissue formation.  

Another special qualification of  chitosan is to inhibit some pathogens such as bacteria, fungi, viruses but there is no apparent evidence that chitosan is able to inhibit infections of shrimp such as SEMBV, YHV, taurasyndrome, other bacteria and fungi.

This article will describe how chitosan function inhibit pathogens as follows;

1)  Chitosan to inhibit viral replication

Generally, virus has simple structure consisting of a capsule which is responsible for protecting the delicate DNA of virus within capsule.  When exposed to virus, chitosan will contact with the DNA of virus and make it malfunction and the genetic cannot be transferred.  Because of high cationicity of chitosan polymer, it attacks itself to the DNA of virus and eventually destroys it.

2)  Chitosan to inhibit bacteria growth in many ways.

     1. With the high efficacy of positive charge, chitosan will contact with negative charge of bacteria cell wall such as N-acetyl Muramic Acid, Sialic Acid and Neuraminic Acid and make the transfer of nutrients and minerals changed causes imbalance chemical of bacteria cell.

     2. The low molecular of chitosan is chelated through cell wall to contact with the transition metal in bacteria cell which ceases synthesis system that is important to the growth of bacteria. 

     3. Chitosan functions as pennicilin to deferiorate bacteria enzyme and incomplete the formation of bacteria cell wall.  When the transfer of nutrients and essential substances to bacteria growth is changed, bacteria cell will be fractioned and died finally.

 

There is a research applying chitosan to control pathogens by using 20,000 ppm concentrated chitosan (2,000 in 1,000,000) contact with pathogens in the plate for 14 days.  The tested pathogens are as followed;

1.)  Coliforms

2.)  Pseudomonas aesuginosa

3.)  Salmonella typhimurium

4.)  Aeromonas hydrophila

5.)  Vibrio cholera

6.)  Escherichia coli

7.)  Shigella dysenteria

It is resulted that chitosan significantly reduces some pathogens when compared with control sample. 

3)  Chitosan to inhibit fungi growth

     Chitosan is quite effective in inhibiting growth of various fungi.  Chitosan is able to induce fungi structure to generate chitin deacetylase which causes broken tip of fungi and died finally.  

     The mechanisms of chitosan to antifungal activity is that chitosan will contact with growing tip of fungi and embed itself into fungi cell.  Due to chitosan and fungal tip have the same structure of amino sugar, chitosan will attack the growing fungi tip to generate chitin deacetylase enzyme that transforms chitin in fungal tip structure into chitosan which is less stable than chitin with chitosan structure. The fungi tip is easily weaken and broken that causes leaking out of all essential substances in fungi and fungi are not able to grow well and finally died.

From the informations aboved, chitosan is applied to control various fungi growth.  However , Chitosan is not an antibiotic.  It successfully inhibits some pathogens, but on the contrary, chitosan itself  is easily digested by enzymes from some pathogens as well.  Therefore, chitosan is another useful alternative to control some pathogens.  The actual benefit of chitosan in liquid form to coat shrimp feed is to enhance shrimp molting and good health.  Chitosan helps perfect shrimp molting, strong health, solid and glossy shell. Chitosan is extracted from shrimp shell so it is safe to shrimp and consumer.