DNA barcoding for species identification in Malaysian processed fish products

Abstract

Currently, high occurrence of mislabelling and species substitution in fish products either intentionally or unintentionally for profit gain has been reported globally, including Malaysia. Such circumstance has urged for increased traceability of fish and the authenticity of raw material to ensure food safety and quality. DNA barcoding offers a rapid, accurate and cost-effective system for species identification via the use of short, standardized mitochondrial marker genes. This study aimed to investigate the prevalence of mislabelling and substitution among fish products in Malaysia market through DNA barcoding approach by targeting the sequence analysis of mitochondrial cytochrome b (Cytb) gene and cytochrome c oxidase subunit I (COI) gene. A total of 18 commercial fish products consisting of various processed state were collected from local sources. DNA was successfully extracted from 12 samples (66.67%). Out of the 12 samples, eight samples (66.67%) exhibited successful amplification of Cytb barcode (287 bp) by a newly designed primer developed in this study. In contrast, only two COI barcodes (~650 bp) from two samples (16.67%) were successfully amplified using fish COI universal primer due to its larger amplicon size, suggesting Cytb serve as a better DNA barcode marker. In total, 10 barcodes (eight Cytb barcodes and two COI barcodes) were generated, direct sequenced and compared to BOLD and GenBank database. All products were successfully identified up to species level. The analysis showed that only one (S20) out of eight samples (12.5%) was found to be substituted with a different species (Escolar) which is dangerous for human consumption as it can cause gastrointestinal problems. Furthermore, two eel samples (S17 and S19) were confirmed as threatened species which raise further concern on the trading of processed fish products from the perspective of conservation and highlights the need for the sustainable management of aquatic resources. These findings conclude DNA barcoding as a reliable tool for species identification and suggest Cytb could serve as an effective marker for authentication of processed fish products as well as conservation management of fish resources.