The use of immobilised bacteria cross-linked within magnetic alginate beads enhances the treatment of benzophenone-type UV filter chemicals by the SBR system.

Benzophenone-n compounds (BPs) are applied in a broad spectrum of commercial products, one of which is sunscreen. These chemicals are frequently detected in a variety of environmental matrices worldwide, especially water bodies. BPs are defined as emerging contaminants as well as endocrine-disrupting contaminants; thus, it has become necessary to develop aggressive and green treatments to remove BPs. In this study, we used immobilised BP-biodegrading bacteria linked to reusable magnetic alginate beads (MABs). The MABs were added to a sequencing batch reactor (SBR) system to enhance the removal of 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3) from sewage. The BP-1 and BP-3 biodegrading bacteria in the MABs consisted of strains from up to three genera to allow for efficient biodegradation. The strains used were Pseudomonas spp., Gordonia sp., and Rhodococcus sp. The optimal composition of the MABs consisted of 3% (w/v) alginate and 10% (w/v) magnetite. The MABs resulted in 60.8%-81.7% recovery by weight after 28 days, and there was a continuous release of bacteria. Moreover, the biological treatment of the BPs sewage improved after adding 100 g of BP1-MABs (1:27) and also 100 g BP3-MABs (1:27) into the SBR system at a hydraulic retention time (HRT) of 8 h. Compared with the SBR system without MABs, the removal rates of BP-1 and BP-3 increased from 64.2% to 71.5% and from 78.1% to 84.1%, respectively. Furthermore, the COD removal increased from 36.1% to 42.1%, and total nitrogen increased from 30.5% to 33.2%. Total phosphorus remained constant at 29%. The bacterial community analysis showed that the Pseudomonas population was <2% before the MAB addition, but increased to 56.1% by day 14. In contrast, the Gordonia sp. And Rhodococcus sp. Populations (<2%) remained unchanged throughout the 14-day treatment period.

Synthesis of cross-linked magnetic chitosan beads immobilised with bacteria for aerobic biodegrading benzophenone-type UV filter.

Bacterial immobilisation is a technique by which bacteria are embedded into or adsorbed onto a carrier material thereby increasing bacterial tolerance to harsh environments. This technique can be used to enhance bacterial activity and to degrade pollutants. Immobilised bacterial beads that contain nanomagnetic particles allow bead recycling and reuse. In this study, our objective was to produce cross-linked nanomagnetic chitosan beads (MCBs) for the biodegradation of benzophenone-type UV filter chemicals such as 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3). We found that the optimal concentration for creating these MCBs to be 1.2% by weight chitosan and 10% by weight nano-magnetite. We selected and isolated six benzophenone-n (BPs)-biodegrading bacteria identified to be various Pseudomonas spp., a Gordonia sp., and Rhodococcus zopfii; these were used to create MCBs that were able to effectively biodegrade BP-1 or BP-3 as a sole carbon source. Both BPs were effectively biodegraded and mineralised over 8 days in the presence of the selected MCB-immobilised bacterial strains. The highest pseudo-first-order constant rates for BP biodegradation were 8.7 × 10-3 h-1 for BP-1 (strain BP1-D) and 1.02 × 10-3 h-1 for BP-3 (strain BP3-1). The mechanical strength of the MCBs was measured to be above 90% based on recovered weight. The MCBs released their bacteria at rates in the range of 104-105 CFU/day. We also determined the pathway through which the BPs were being aerobically biodegraded based on the GC/MS profiles of the intermediates. Our findings provide a novel strategy for treating BPs via the use of reusable and recyclable MCBs that are cheap, easy and fast to synthesise.