| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 104 === Based on pigmentation, macroalgae can be classified as brown algae (Phaeophyceae), red algae (Rhodopyceae) and green algae (Chloropyceae). Recently, macroalgae are regarded as great potential sources of plant proteins with increasing need. In this study, green algae Ulva lactuca was selected due to its protein content (3.45–29.00 %, dry basis), which is moderately high in green algae group. The objectives were to evaluate the protein extraction methods in Ulva lactuca, to identify molecular characteristic using polyacrylamide gel electrophoresis (SDS–PAGE) and proteomics techniques, to predict bioactive peptides and the potential biological activities in using bioinformatics tools (UniProt/KB and BIOPEP database). In order to isolate the protein fraction from green algae, two extraction methods were performed: aqueous and alkaline (0.1 M NaOH) extraction, and precipitate using 10% TCA/acetone. Alkaline extraction had the highest yield (17.29 ± 4.38%) than aqueous extraction (14.77 ± 6.86%). With SDS-PAGE characterization, molecular weight (MW) of protein subunits were identified as follows: 34.6 kDa (A1), 23.7 kDa (A2), 10 kDa (A3) and 13.4 kDa (B1). The protein bands A1, A2 and B1 were comparable with reported Ulva sp protein sequence; (A1) elongation factor Tu (MW: 32.7 kDa), (A2) ferritin (MW: 22.2 kDa) and (B1) cytochrome b6/f complex subunit IV (MW: 12.8 kDa) protein. The subsequent in silico analysis was carried out using BIOPEP database to predict bioactive peptides with reported biological activities. The predictive results showed that the Ulva lactuca proteins have the highest occurrence frequency of potential bioactivities in dipeptidyl peptidase (DPP)-IV inhibitors, followed by angiotensin converting enzyme (ACE) inhibitors, antioxidative, antiamnestic, antithrombotic, and a small amount of antibacterial and neuropeptide. In silico hydrolysis using “BIOPEP” enzyme action tools” with 27 proteases revealed that hydrolysis with ficain (elongation factor Tu), papain (ferritin) and proteinase K (cytochrome b6/f complex subunit IV) released greater numbers of predicted bioactive peptides compared to others proteases.
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