Production of N-acetyl-chitooligosaccharides by hydrolysis of shrimp shell of various particle sizes using Bacillus cereus NTU-FC-4
Date Issued
2008
Date
2008
Author(s)
Tsa, Yi-Jie
Abstract
N-acetyl-chitooligosaccharides are composed of 2–10 N-acetyl-glucosamine residues with β-1,4-linkage to form low molecular weight oligomer. The N-acetyl-chitooligosaccharides have numerous bioactive functions, including anti-bacterial, antitumor, and tissue repair properties. It is also known that high degree polymerized oligomers, such as N-acetylchitohexaose and N-acetylchitoheptaose, have better biological function compared to other N-acetyl-chitooligosaccharides. Traditionally, chitin are produced from crustaceans (like shrimp shell) by a strong acid and base chemical procedure, and then hydrolysis of the chitin is carried out to produce N-acetyl-chitooligosaccharides. However, the use of strong acid and base makes this procedure environment unfriendly. The objective of this study was to incorporate medium milling technology to reduce the particle size of shrimp shell, thus it can be used directly for the production of N-acetyl-chitooligosaccharides. Various carbon sources, inculding colloidal chitin, glucose, chitosan powder, D-glucosamine and N-acetyl-D-glucosamine, were used to cultivate Bacillus cereus NTU-FC-4 to induce enzyme. It was found that the highest activity (0.45 unit/mL) of the chitinase produced by the Bacillus cereus NTU-FC-4 was obtained when the cultivation was carried out in the medium containing colloidal chitin, suggesting that Bacillus cereus NTU-FC-4 was an inductive chitinase producer. The steamed or non-steamed shrimp shell was processed by medium milling technology to reduce particle size, then, the suspension containing shrimp shell particle was used to cultivate Bacillus cereus NTU-FC-4. The results indicated that the chitinase produced by the Bacillus cereus NTU-FC-4 was about 0.48 unit/mL when the microorganism was cultivated in the medium containing 1.5% of 10 mm steamed shrimp shell. And the chitinase produced by the Bacillus cereus NTU-FC-4 was about 0.45 unit/mL when cultivated in the medium containing 1.5% of 10 mm non-steamed shrimp shell. Besides, it was also found that 48 hours of cultivation time could induce the highest amount of enzyme. Using shrimp shell of different particle sizes to cultivate Bacillus cereus NTU-FC-4 directly, it was found that the hydrolysate contained various chitooligomers, including monomer to hexamer. By hydrolyzing shrimp shell of different particle sizes by crude chitinase from Bacillus cereus NTU-FC-4, the main hydrolysate were N-acetylglucosamine and N-acetylchitobiose, and the intermediates were N-acetylchitotetraose, N-acetylchitopentaose, and N-acetylchitohexaose. It is interesting to note that the N-acetyl-chitooligosaccharides concentrations in the product yielded from the microorganism were generally higher than that yielded from the crude chitinase. In addition, the smaller the shrimp shell particle used, the higher the concentration of N-acetylglucosamine and N-acetylchitobiose could be obtained during crude chitinase hydrolysis. Results of this study demonstrated that particle size reduction was an effective method to facilitate enzymatic hydrolysis of shrimp shell.
Subjects
shrimp shell wastes
green technology
different particle sizes
chitinase
N-acetyl-chitooligosaccharides
Bacillus cereus NTU-FC-4
Type
thesis
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