Abstract
Previous studies have demonstrated that plastic particles (PLA), degraded from food packaging waste, have high affinity with heavy metals (HM) that result in a worse combined marine plastic pollution than plastic pollution alone. Chitosan and zein-based edible food film (CZF) is biodegradable and environmentally friendly which could be considered as an alternative material to reduce the plastic pollution. On the other hand, the heavy metals bound to PLA could induce oxidative stress disrupting the amino acid metabolism of fish, hence there is a need to evaluate whether CZF can reduce the heavy metal complex formation as well as the resulting oxidative stress that affects the amino acid metabolism of fish. The heavy metals came from the contaminants originally present in the ingredients used in the film making.
For this study, Triplefin-fish (Forsterygion capito, TPN-fish), a local species found in New Zealand waters was selected as our model organism due to its integral role within marine ecosystems, particularly in contributing to the lower levels of marine food chains. We exposed them to PLA and CZF at similar dosage and frequency for the same predefined feeding time (39 days). The profile of amino acid pool was measured only in the muscle portion of the fish. Based on the literature review, analysis of the free amino acid (FAA) pool was selected as a key biomarker to evaluate the effects of CZF and PLA exposure on TPN-fish muscle. The FAA pool profiling was conducted using gas chromatography with flame ionization detector (GC- FID) as an analytical approach. Multivariate and univariate statistical approaches, namely principal component analysis (PCA) and orthogonal partial least squares–discriminant analysis (OPLS-DA), and Mann–Whitney U test and one-way analysis of variance (ANOVA), were used to identify FAA discriminators associated with exposure to CZF and PLA. The identified discriminators were further evaluated by pathway analysis to identify potentially affected areas of amino acid metabolism.
The FAA pool in the white muscle of TPN-fish exposed to CZF was found to be altered, including a decreased level of branched chain amino acids (BCAAs), serine, methionine, phenylalanine, histidine, tyrosine, tryptophan, ornithine, and an increased level of alanine and glutamine. In addition, specific impacted pathways were identified in relation to the change in the FAA pool, namely phenylalanine, tyrosine and tryptophan biosynthesis; alanine, aspartate, glutamic acid and glutamine metabolism; valine, leucine and isoleucine biosynthesis. Overall, the altered amino acid metabolism was attributed to abnormal energy metabolism, reduction of weight gain and a disturbed immune system in TPN-fish. Moreover, the decreased levels of phenylalanine, tryptophan and histidine were found to be associated with changes in fish behaviour and swimming performance. The present study has demonstrated that FAA pool profiling can be a robust and effective approach in monitoring the biophysical effects of exposing TPN-fish to CZF.
This study was the first to use GC-FID based FAA pool profiling to investigate the effect of an alternative food packaging material (CZF) in a New Zealand aquatic ecosystem. Evaluation of the FAA data indicated that this approach could specifically contribute to the evaluation of the safety of CZF in the environment. The results of the present study also provide a preliminary framework in relation to the application of FAA profiling to evaluate metabolic changes in a model organism, on exposure to an alternative food packaging material, and its potential effect on the environment.