Crude tissue proteins were extracted from the underutilized marine bivalves: Placuna placenta, Placuna
ephippium, Scapharca inaequivalvis, and Marcia hiantina by aqueous and acidic extraction methods. Partial
purification of the crude extracts was done through ammonium sulfate precipitation followed by membrane
dialysis. The resulting filtrate was then subjected to centrifugal ultrafiltration to produce fractions of 10-20 kDa
molecular weight. Highest total soluble proteins were observed in M. hiantina extracts at 16.20 mg/ml for hot
water extraction (HWE), 11.13 mg/ml for cold water extraction (CWE), and 11.68 mg/ml for acetic acid extraction
(AAE) (P<0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) bands indicate low
molecular weight peptides (<14 kDa) were present in HWE and AAE extracts of P. placenta and CWE of S.
inaequivalvis. Highest 2, 2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity was observed in M. hiantina
CWE at 54.09 % (P < 0.05). Highest antibacterial activity against Bacillus cereus was observed in AAE and
HWE extracts of P. placenta, with minimum inhibitory concentration (MIC) of 124.34 μg/ml and 195.71 μg/ml,
respectively. Results of this study indicate that the protein extracts of these underutilized marine bivalves may
have promising antioxidant and antibacterial activities which can be potential sources of bioactive compounds.
It also confirmed the potential of using aqueous extraction to liberate the peptides, which is a more costeffective
alternative to chemical and enzymatic hydrolysis.