Effects of poly(3-hydroxybutyrate) [P(3HB)] coating on the bacterial communities of artificial structures.

The expanding urbanization of coastal areas has led to increased ocean sprawl, which has had both physical and chemical adverse effects on marine and coastal ecosystems. To maintain the health and functionality of these ecosystems, it is imperative to develop effective solutions. One such solution involves the use of biodegradable polymers as bioactive coatings to enhance the bioreceptivity of marine and coastal infrastructures. Our study aimed to explore two main objectives: (1) investigate PHA-degrading bacteria on polymer-coated surfaces and in surrounding seawater, and (2) comparing biofilm colonization between surfaces with and without the polymer coating. We applied poly(3-hydroxybutyrate) [P(3HB)) coatings on concrete surfaces at concentrations of 1% and 6% w/v, with varying numbers of coating cycles (1, 3, and 6). Our findings revealed that the addition of P(3HB) indeed promoted accelerated biofilm growth on the coated surfaces, resulting in an occupied area approximately 50% to 100% larger than that observed in the negative control. This indicates a remarkable enhancement, with the biofilm expanding at a rate roughly 1.5 to 2 times faster than the untreated surfaces. We observed noteworthy distinctions in biofilm growth patterns based on varying concentration and number of coating cycles. Interestingly, treatments with low concentration and high coating cycles exhibited comparable biofilm enhancements to those with high concentrations and low coating cycles. Further investigation into the bacterial communities responsible for the degradation of P(3HB) coatings identified mostly common and widespread strains but found no relation between the concentration and coating cycles. Nevertheless, this microbial degradation process was found to be highly efficient, manifesting noticeable effects within a single month. While these initial findings are promising, it's essential to conduct tests under natural conditions to validate the applicability of this approach. Nonetheless, our study represents a novel and bio-based ecological engineering strategy for enhancing the bioreceptivity of marine and coastal structures.

Insights into biofilm development on polyhydroxyalkanoate biofilm carrier for anoxic azo dye decolourization of acid orange 7.

Polyhydroxyalkanoates (PHAs) are promising alternatives to non-degradable polymers in various applications. This study explored the use of biologically recovered PHA as a biofilm carrier in a moving bed biofilm reactor for acid orange 7 treatment. The PHA was comprised of 86 ± 1 mol% of 3-hydroxybutyrate and 14 ± 1 mol% of 3-hydroxyhexanoate and was melt-fused at 140 °C into pellets. The net positive surface charge of the PHA biocarrier facilitated attachment of negatively charged activated sludge, promoting biofilm formation. A 236-µm mature biofilm developed after 26 days. The high polysaccharides-to-protein ratio (>1) in the biofilm's extracellular polymeric substances indicated a stable biofilm structure. Four main microbial strains in the biofilm were identified as Leclercia adecarboxylata, Leuconostoc citreum, Bacillus cereus, and Rhodotorula mucilaginosa, all of which exhibited decolourization abilities. In conclusion, PHA holds promise as an effective biocarrier for biofilm development, offering a sustainable alternative in wastewater treatment applications.