Abstract Description

Seaweeds are a promising source of bioactive compounds known to possess antioxidant, antiviral, antimicrobial, and anticoagulation properties, which makes seaweed an attractive source for biotechnological applications. Brown seaweed is particularly interesting – it is rich in fucoidan and alginate, both associated with numerous health benefits. When plastic waste enters the marine environment, microplastics (MPs) are formed due to biotic and abiotic processes. Many studies have detailed the severe effects of MPs on marine organisms. However, none of these studies have focused on the effect of MPs on seaweed degradation, a natural process that releases valuable nutrients into the marine environment. The aim of this study was therefore to determine the effect of MPs on the ability of carbohydrate-active enzymes (CAZymes) to degrade seaweed and the release of biotechnologically valuable bioactive compounds exhibiting antimicrobial and antioxidant activities. Brown, green, and red seaweed were collected along the Cape Town coastline, and were dried and ground, defatted, depigmented, and in the case of the brown seaweed, the fucoidan and alginate components were extracted. The CAZymes, fucoidanase (Wf GH168), cellulase from Trichoderma reesii, and the small laccase from Streptomyces coelicolor, were produced and purified for application in seaweed degradation. The release of reducing sugars was monitored, and the optimal combination of enzymes will be applied in future studies to determine whether MPs have an inhibitory effect on the efficacy of the CAZymes. The degradation products from these treatment experiments will then be assessed for antimicrobial activity, antioxidant activity, and cytotoxicity. Studies on MPs in the marine environment are usually focused on their impacts on marine organisms and environmental health. However, this first-of-a-kind study will provide insights into the potential interfering role of MPs in natural processes that occur in the marine environment and a bioprocess that plays a key role in accessing the biotechnological potential of seaweed, a resource that contributes to the global Oceans Economy.