Polyesterase activities in bacterial isolates from seaweed and sponges, with potential utility in polyethylene terephthalate plastic and nanoparticle hydrolysis

Many marine bacteria have evolved to produce a range of extracellular enzymes which facilitate their growth and survival in the harsh, oligotrophic conditions often present in marine environments. Marine sponge derived Streptomycesstrains have previously been reported to produce polyesterase enzymes, which are of interest for several biotechnological applications, including polyethylene terephthalate (PET) plastic hydrolysis. Bacteria isolated from sponges and seaweed were screened for polyester hydrolysis activities using plate-clearing assays. Lipolytic and polyesterolytic activities were initially identified by employing tributyrin and polycaprolactone diol agar-based assay systems, respectively. Polyesterase activity was subsequently confirmed on both polycaprolactone and on PET-nanoparticle agar plates, resulting in the prioritisation of six isolates for Illumina next-generation genome sequencing. These include three Bacillusspp., isolated from the brown seaweed Ascophyllum nodosum,and from marine lake sponges Stelligera stuposaand Eurypon major, together with a Maribacterstrain again isolated from S. stuposa, and Brachybacteriumsp. and Micrococcussp. isolates of deep-sea sponges Pheronemasp. and Inflatella pellicula, that were sampled at depths of 2129m and 2900m, respectively. Genome mining and comparative genomic analysis of these isolates is currently underway to identify genes encoding the observed activities and to assess homology with known PET hydrolases. Microbes found living in association with filter-feeding sponges may have increased exposure to the plastics and microplastics that widely contaminate our marine ecosystems, thus representing a promising source of degradative activities towards synthetic polymers that could contribute to new plastic waste management strategies.