Fish, chitin, and chitosan production 299openness, candour, public education and public involvement appear to be the
keys to public acceptance. In spite of the many problems, the future for waste-
fish recycling systems seems promising This is due to the ever increasing
demands for both waste disposal and food production in today's rapidly
expanding populations.
6.8 Chitin and chitosan production
The conventional process of chitin production from shrimp shells consists of (a)
alkaline treatment of deproteination by using 4% NaOH at 30oC for 24 hours
and (b) acid treatment or decalcification by using 4% HCl at 30oC for 24 hours.
Chitin is polysaccharides polymers made up of a linear chain of N-
acethylglucosamine groups as shown in Figure 6.16.
Figure 6.16 Chemical structures of chitin and chitosan
Chitosan is obtained by a process called deacethylation, which treats the
chitin compounds in 50% NaOH solution for 24 hours at 30oC or ambient
temperatures. The deacethylation reaction remove acethyl groups (CH 3 -CO)
from the chitin molecules and makes the product, chitosan (see Figure 6.16),
cationic in characteristic and soluble in most dilute acids. A schematic diagram
of chitin and chitosan production from shrimp shells is shown in Figure 6.17.
To produce chitin from 100 kg of fresh shrimp shells, about 250 L of 4%
NaOH and 250 L of 4% HCl would be required for the deproteination and
decalcification, respectively; while about 80 L of 50% NaOH is needed for the
deacethylation. Chitin content in shrimp shells is in the range of 10-20%.
Chitin ChitosanCH 2 OH CH 2 OHNHCOCH 3 NHCOCH 3OH OHOOOCH 2 OH CH 2 OHNH 2 NH 2OH OHOOO