The easy way is the chtinase producers like B. sp and u can obtain them free from NRRL.(culture collection)

Do you have included temperature in the acid hydrolysis? What?

I have tried temperatures between 40C and 80C for acid hydrolysis.

The temperature of hydrolysis at 80C is good, but 90C is better. And the time and acid concentration is very important too: if HCl 9-11 M - 8 hs; if 60C: HCl 9-11 M - 10-12 hs. And to you consider: chitin can be hydrolyzed with other enzymes, of lower cost, such as cellulases, pectinases and lysozymes, beyond chitinases.

You could deacetylate the chitin (flakes or powder?) in 50% w/w NaOH at 70°C for 3-4 hours (1 g chitin to 10 g NaOH) in the fume hood. Then wash the sample with plenty of distilled hot water. Dry the sample in 70°-80°C overnight. There you have chitosan witch is deacetylated chitin. You can re-acetylate the amide groups with acetic anhydride (make chitin again), see http://www.groupes.polymtl.ca/tissue/Publications/PDFs/12186.pdf

You have to dissolve the chitosan in 0.5-1.0% acetic acid.

Why bother all this? If you dissolve the chitin as chitosan, you open up the closed structure of the chitin in the shell and dissolve the polysaccharide. To reacetylate the polysaccharide you have made easily soluble chitin which is a great substrate for chitinolytic bacterial fermentation since these organisms excrete chitinases which brake the polymer into N-acetyl glucosamine.

I hope this is helpful.

It is a routine industrial process to produce N-acetyl glucosamine from chitin. if you find chemical process not suitable enough, you can try the enzymatic process. Now a days, chitinases are available commercially with several fine chemicals / biologicals manufacturers, for a reasonable price. Good luck.