Comparative degradability of polypropylene (PP) microplastics by two efficient floc-forming bacteria, Bacillus cereus and Bacillus infantis, isolated from a commercial aquafarm Shahadat Hossain1, Zuhayra Nasrin Ahmad Shukri1, Khor Waiho1, Yusof Shuaib Ibrahim2 Amyra Suryatie Kamaruzzan1, Ahmad Ideris Abdul Rahim1, Zahidul Islam3, Nor Azman Kasan*1,2
1Higher Institution Centre of Excellence (HICoE), Institute of Tropical Aquaculture and Fisheries, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia.
2Microplastic Research Interest Group (MRIG), Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
3Marine Fisheries and Technology Station, Bangladesh Fisheries Research Institute, Cox^s Bazar Sadar-4700, Cox^s Bazar, Bangladesh.
*Corresponding author: Nor Azman Kasan, Higher Institution Centre of Excellent (HICoE), Institute of Tropical Aquaculture and Fisheries, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia. Email: norazman[at]umt.edu.my
Abstract
Microplastics pollution in aquaculture has got recent attention due to the wide usage trends of plastics in aquaculture operations. Microplastics especially polypropylene (PP), are one of the most commonly found MPs in the aquaculture environment in recent studies. A popular technology called biofloc technology (BFT) uses floc forming microorganisms to alleviate water pollutants in the aquaculture environment. The potentiality of the floc-forming bacteria in treating the MPs particles in water is rarely studied. This study aimed to investigate the comparative potentialities of two effective floc forming bacteria, Bacillus cereus, and B. infantis in degrading PP microplastics. The bacteria were isolated from a commercial aquafarm, and identified by using 16s rRNA sequencing. Floc forming ability was measured in kaolin clay suspension. After the incubation of the identified bacteria in mineral salt media for 60 days, the biodegradation ability was evaluated by measuring the weight loss of microplastics, optical bacterial growth, bacteria colony growth, microplastics surface characterization, and detecting alterations in chemical compositions by FTIR spectroscopy. B. cereus showed a higher flocculation activity, 93.66% than B. infantis (88.64%). Overall, B. cereus showed significantly higher degradability by showing higher bacterial colony growth, weight loss (4.61%), optical bacteria growth, microplastic surface changes, and changes in chemical composition. In conclusion, the study showed floc forming bacteria can degrade PP microplastics and B. cereus can be an effective microplastics degrader that can ensure a sustainable pollution free aquaculture system.
Keywords: Microplastics pollution, polypropylene, biofloc technology, biodegradation ability, weight loss
