Characterization and Gene Sequence Analysis of a Cellulase from Sea Hare Aplysia juliana

• Main Authors: Jyun-Ming Liao, 廖駿銘
• Other Authors: Jiun-Hong Chen
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/35666056427758710907

碩士 === 國立臺灣大學 === 動物學研究所 === 100 === Marine algae have high content of energy rich carbohydrates or oil and possess comparable potential for bioenergy production like terrestrial plants. Macroalgae, namely seaweeds, contained cellulose without lignin are much easier to be converted into bioethanol than lignocellulose from terrestrial plants. However, the process to harvest seaweed and to isolate cellulose might increase the salinity of the cellulose product. To avoid the fresh water wash step, cellulases that have high activity in high salinity condition are required to breakdown the cellulose efficiently. Because invertebrates inhabited intertidal zone have to adapt the concentration changes of seawater during the low tide, they are potential source of cellulase suitable for digesting seaweed cellulose. Recently, 15 marine invertebrates, which are common species at the northeastern coast in Taiwan, have been screened for their cellulase activities. The digestive juice of sea hare Aplysia juliana showed the highest cellulase activity at 55℃. Furthermore, A. juliana digestive juice could tolerate higher salt concentration than the cellulases from two fungi, Aspergillus niger or Trichoderma viride. An 1163bp cDNA partial sequence of A. juliana cellulase gene (AjCel) has been cloned and the gene expression was identified in esophagus, crop, gizzard and stomach. The result of sequence analysis showed the cellulase of A. juliana belongs to glycosyl hydrolase family 9 (GHF-9) and the catalytic residue is conserved through evolution. These data suggest that A. juliana cellulase is an endogenous cellulase which has high potential for bioethanol production in the future.