JOBIMB, 2019, Vol 7, No 1, 10-16 - 10 - pH Shift Solubilization and Precipitation Protein Extraction from the Wastes of the Threadfin Bream, Nemipterus japonicus Noorsuliya Raihan 1 , Sahar Abbasiliasi 1 *, Joo Shun Tan 2 , Malihe Masomian 3 , Tengku Azmi Tengku Ibrahim 4 , Arbakariya B Ariff 5 and Shuhaimi Mustafa 1,6, * 1 Halal Products Research Institute, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. 2 Bioprocess Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Gelugor, Pulau Pinang, Malaysia. 3 Centre For Virus and Vaccine Research, School of Science and Technology, Sunway University, Kuala Lumpur, Selangor 47500, Malaysia. 4 Faculty of Veterinary Medicine, Universiti Putra Malaysia, 43400 Upm Serdang, Selangor, Malaysia. 5 Bioprocessing and Biomanufacturing Research Center, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. 6 Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. *Corresponding author: Sahar Abbasiliasi (Dr.) & Shuhaimi Mustafa (Prof. Dr.) Halal Products Research Institute, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Emel: sahar@upm.edu.my; shuhaimi@upm.edu.my INTRODUCTION The fish industry produces more than 60% waste comprising of the fish head, skin, trimmings, fins, frames, viscera and roes. This huge quantity of waste is usually discarded which led to serious pollution and disposal problems. However, some of these wastes, from the perspective it is protein-rich could be processed and converted into fish meal which is a component in the formulation of animal feed. It is widely known that in animal production 70% of cost is attributed to feed. Nevertheless, fish waste could be converted into protein hydrolysates which could make them highly functional and bioactive. Several methods have been developed directed towards protein isolation which involve solvent extraction, heat treatment, enzyme/acid hydrolysis, repeated water washing and HISTORY Received: 11 th March 2019 Received in revised form: 24 th of April 2019 Accepted: 25 th of June 2019 ABSTRACT This study aimed at extraction of protein from the wastes of the threadfin bream, Nemipterus japonicus using pH shift solubilization and precipitation processes and evaluation of the influencing factors on protein extraction. Towards this objective, the wastes of head, skin and internal organs were collected, and their nutritional composition evaluated. Furthermore, the ratio of waste: water for protein extraction was screened and the effect of pH, centrifugation speed and time on protein solubility rate, the amino acid composition and the molecular weight of proteins via SDS-PAGE were determined. Results demonstrated that moisture was the highest percentage (~70-78%) of all wastes. Highest protein content (19.67±1.10%), fat content (1.81±0.09%) and carbohydrate content (4.43±0.23%) were observed in skin, head and internal organs, respectively. The optimum ratio of waste: water for protein extraction is 1:9 for head, 1:8 for internal organs and 1:6 for skin. The protein extraction efficiency for all three samples were high at pH 3 and pH 12. Protein solubility increased with increased centrifugation speed up to 10,000 ×g, and there was no significant difference (P>0.05) between the protein solubility at 10,000 ×g and 20’000 ×g. Furthermore, there was significant difference (P<0.05) between protein solubility with increased centrifugation time. Alkaline process showed a remarkably higher amino acid content as compared to that of acid version. Glutamic acid and lysine were found higher compared to other amino acids. The molecular weight of proteins isolated in this study were low (<100 KDa). KEYWORDS waste solubilization precipitation protein pH-shift process JOURNAL OF BIOCHEMISTRY, MICROBIOLOGY AND BIOTECHNOLOGY Website: http://journal.hibiscuspublisher.com/index.php/JOBIMB/index JOBIMB VOL 7 NO 1 2019 Per ARNT SIM Domain Gene distribution in normal human testis cell