The total global demand for protein from both humans and livestock will rose substantially into the future due to combined increase in population and per capita consumption of animal protein. Currently, net protein is primarily produced by agricultural crops. However, the future production of agricultural crops is limited by a finite supply of arable land, fresh water and synthetic fertilizers. Alternative protein sources and production methods are required to fulfil the demand of consumers and to meet predicted global protein requirements. Seaweeds as alternative crops have the potential to help meet the protein demand without applying the additional stress on traditional agricultural resources. This thesis investigates the potential of seaweed as an alternative crop for production of protein. This research was conducted in four different studies. In the first study, application of response surface methodology (RSM) for enzymic treatment optimization of Gelidiella acerosa was investigated in order to improve the extraction of algal proteins using Viscozyme and Celluclast. The total protein, soluble proteins and reducing sugar recovery in the water-soluble fraction were studied in relation to the hydrolysis time, type and concentration of the enzymes. Enzymatic digestion appeared to be an effective treatment for protein extraction. While enzyme hydrolysis by Celluclast was able to facilitate the protein extraction, it was a relatively inefficient way to improve protein extraction yield, in comparison with Viscozyme. The optimum conditions for protein extraction were found to be hydrolysis by 2.8 µl ml -1 of Viscozyme L for 12h. Eencouraged by non-thermal, chemical-free and energy efficiency properties of HVED processes, we set out to test the working hypothesis that HVED will enable protein extraction from G. acerosa in the second study. We found that application of 900 electric discharge with electrodes distance of 10 mm in a liquid-to-solid ratio of 60, pulse repetition rate of 0.5 Hz and combined with enzyme hydrolysis of the treated samples for 4 g by 2 µl ml -1 of Viscozyme led to selective extraction of water soluble proteins. There was no significant difference in protein concentration between enzymic hydrolysis and this method of extraction (p 0.05). In the third study, RSM was used to determine the optimal conditions for enzymic extraction of peptides by Alcalase from proteins extracted in optimal conditions of enzymic hydrolysis (E) and HVED-assisted enzyme hydrolysis (H). The highest DH was obtained when hydrolysis time and ratio of enzyme to substrate were 3 h and 4% in optimum temperature and pH (55 o C, 8.0), respectively. UF was used to fractionation of peptides on the base of molecular weight (MW: 1, 3, 5, 10 and 30 kDa). Additionally, antioxidative, ACE inhibitory activity, and antibacterial properties of peptide fractions were described. We used the DPPH assay to evaluate the capacity of E and H peptides to quench radical species. All H peptides exhibited higher scavenging effect than that of E. The higher radical scavenging capacity from hydrolysates could be due to the low MW peptides. Hydrolysates showed good antihypertensive activity (higher than 60% of ACE inhibition). The ACE inhibitory activities of the hydrolysates varied with the molecular weight distribution, and the peptides with MW below 5 kDa showed the most potent ACE inhibitory activity. Antibacterial activity was evaluated against Gram negative and Gram-positive bacteria and none of peptides have activity against bacteria. In forth study, hydrolysates were analysed using RP-HPLC-ESI-Quadrupole-Time-of-Flight (Q-TOF) system. Finally, analysis of data was performed by the de novo sequencing tool. Analysis of hydrolysate enabled the identification of 23 peptides in H peptides and 17 in E peptides with typical features of antioxidant and antihypertensive peptides. Identified peptides in fractions showed less than 10 amino acids and a high number of hydrophobic and aromatic amino acids, which are characteristic features for antioxidant and antihypertensive peptides. Key Words Gelidiella acerosa, protein extraction, enzyme hydrolysis, HVED, biopeptide, antioxidant activity, ACE inhabitation, RP-HPLC-ESI- Q-TOF, de novo sequencing.