Enhanced microbial degradation of PET and PS microplastics under natural conditions in mangrove environment.

In-situ bioremediation of mangrove soil contaminated with polyethylene terephthalate (PET) and polystyrene (PS) microplastics was investigated using indigenous microbial consortium with adequate capacity to degrade the plastics. Eight (8) bacteria were isolated from plastic/microplastic-inundated mangrove soil and screened for the ability to degrade PET and PS microplastics. Optical density at 600 nm and colony forming unit counts were measured to evaluate the growth response of the microbes in the presence of PS and PET microplastics at different times of exposure. Structural and surface changes that occurred post biodegradation on the microplastics were determined through EDS and SEM analysis. The obtained results demonstrated the elongation and disappearance of peaks, suggesting that the microbial consortium could modify both types of microplastics. The overall results of the microplastic degradation showed varied degrees of weight loss after 90 experimental days, with the treated plot recorded 18% weight loss. The augmented soil was increased in the concentrations of Si S, and Fe and decreased in the concentrations of C, O, Na, Mg, Al, Cl, and K after bioremediation.

Growth kinetics and biodeterioration of polypropylene microplastics by Bacillus sp. and Rhodococcus sp. isolated from mangrove sediment.

Interest in the biodegradation of microplastics is due to their ubiquitous distribution, availability, high persistence in the environment and deleterious impact on marine biota. The present study evaluates the growth response and mechanism of polypropylene (PP) degradation by Bacillus sp. strain 27 and Rhodococcus sp. strain 36 isolated from mangrove sediments upon exposure to PP microplastics. Both bacteria strains were able to utilise PP microplastic for growth as confirmed by the reduction of the polymer mass. The weight loss was 6.4% by Rhodococcus sp. strain 36 and 4.0% by Bacillus sp. strain 27 after 40days of incubation. PP biodegradation was further confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy analyses, which revealed structural and morphological changes in the PP microplastics with microbial treatment. These analyses showed that the isolates can colonise, modify and utilise PP microplastics as carbon source.

Screening of Bacillus strains isolated from mangrove ecosystems in Peninsular Malaysia for microplastic degradation.

The continuous accumulation of microplastics in the environment poses ecological threats and has been an increasing problem worldwide. In this study, eight bacterial strains were isolated from mangrove sediment in Peninsular Malaysia to mitigate the environmental impact of microplastics and develop a clean-up option. The bacterial isolates were screened for their potential to degrade UV-treated microplastics from polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS). Only two isolates, namely, Bacillus cereus and Bacillus gottheilii, grew on a synthetic medium containing different microplastic polymers as the sole carbon source. A shake flask experiment was carried out to further evaluate the biodegradability potential of the isolates. Degradation was monitored by recording the weight loss of microplastics and the growth pattern of the isolates in the mineral medium. The biodegradation extent was validated by assessment of the morphological and structural changes through scanning electron microscopy and Fourier transform infrared spectroscopy analyses. The calculated weight loss percentages of the microplastic particles by B. cereus after 40 days were 1.6%, 6.6%, and 7.4% for PE, PET, and PS, respectively. B. gottheilii recorded weight loss percentages of 6.2%, 3.0%, 3.6%, and 5.8% for PE, PET, PP, and PS, respectively. The designated isolates degraded the microplastic material and exhibited potential for remediation of microplastic-contaminated environment. Biodegradation tests must be conducted to characterize the varied responses of microbes toward pollutants, such as microplastics. Hence, a novel approach for biodegradation of microplastics must be developed to help mitigate the environmental impact of plastics and microplastic polymers.

Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions.

The presence of microplastics in the marine environment poses a great threat to the entire ecosystem and has received much attention lately as the presence has greatly impacted oceans, lakes, seas, rivers, coastal areas and even the Polar Regions. Microplastics are found in most commonly utilized products (primary microplastics), or may originate from the fragmentation of larger plastic debris (secondary microplastics). The material enters the marine environment through terrestrial and land-based activities, especially via runoffs and is known to have great impact on marine organisms as studies have shown that large numbers of marine organisms have been affected by microplastics. Microplastic particles have been found distributed in large numbers in Africa, Asia, Southeast Asia, India, South Africa, North America, and in Europe. This review describes the sources and global distribution of microplastics in the environment, the fate and impact on marine biota, especially the food chain. Furthermore, the control measures discussed are those mapped out by both national and international environmental organizations for combating the impact from microplastics. Identifying the main sources of microplastic pollution in the environment and creating awareness through education at the public, private, and government sectors will go a long way in reducing the entry of microplastics into the environment. Also, knowing the associated behavioral mechanisms will enable better understanding of the impacts for the marine environment. However, a more promising and environmentally safe approach could be provided by exploiting the potentials of microorganisms, especially those of marine origin that can degrade microplastics. CAPSULE: The concentration, distribution sources and fate of microplastics in the global marine environment were discussed, so also was the impact of microplastics on a wide range of marine biota.

Engineering characterisation of a shaken, single-use photobioreactor for early stage microalgae cultivation using Chlorella sorokiniana.

This work describes the characterisation and culture performance of a novel, orbitally shaken, single-use photobioreactor (SUPBr) system for microalgae cultivation. The SUPBr mounted on an orbitally shaken platform was illuminated from below. Investigation of fluid hydrodynamics indicated a range of different flow regimes and the existence of 'in-phase' and 'out-of-phase' conditions. Quantification of the fluid mixing time (tm) indicated a decrease in tm values with increasing shaking frequency up to 90 rpm and then approximately constant tm values in the range 15-40 s. For batch cultivation of Chlorella sorokiniana, the highest biomass concentration achieved was 6.6 g L(-1) at light intensity of 180 µmol m2 s(-1). Doubling the total working volume resulted in 35-40% reduction in biomass yield while shaking frequency had little influence on culture kinetics and fatty methyl esters composition. Overall this work demonstrates the utility of the SUPBr for early stage development of algal cultivation processes.