Production of microparticles of molinate degrading biocatalysts using the spray drying technique. (October 2016)

• Record Type: Journal Article
• Authors: Lopes, Ana R.; Sousa, Vera M.; Estevinho, Berta N.; Leite, José P.; Moreira, Nuno F.F.; Gales, Luís; Rocha, Fernando; Nunes, Olga C.
• Is Part Of: Chemosphere. Volume 161(2016)
• Page Start: 61
• Page End: 68
• Publication Date: 2016-10
• Subjects: Bioaugmentation -- Calcium alginate -- Modified chitosan -- Microparticles -- Spray-drying; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2016.07.006
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Previous studies demonstrated the capability of mixed culture DC1 to mineralize the thiocarbamate herbicide molinate through the activity of molinate hydrolase (MolA). Because liquid suspensions are not compatible with long-term storage and are not easy to handle when bioremediation strategies are envisaged, in this study spray drying was evaluated as a cost-effective method to store and transport these molinate biocatalysts. Microparticles of mixed culture DC1 (DC1) and of cell free crude extracts containing MolA (MA) were obtained without any carrier polymer, and with calcium alginate (CA) or modified chitosan (MCt) as immobilizing agents. All the DC1 microparticles showed high molinate degrading activity upon storage for 6 months, or after 9 additions of ∼0.4 mM molinate over 1 month. The DC1-MCt microparticles were those with the highest survival rate and lowest heterogeneity. For MA microparticles, only MA-MCt degraded molinate. However, its Vmax was only 1.4% of that of the fresh cell free extract (non spray dried). The feasibility of using the DC1-MCt and MA-MCt microparticles in bioaugmentation processes was assessed in river water microcosms, using mass (g):volume (L) ratios of 1:13 and 1:0.25, respectively. Both type of microparticles removed ∼65–75% of the initial 1.5 mg L −1 molinate, after 7 days of incubation. However, only DC1-MCt microparticles were able to degrade this environmental concentration of molinate without disturbing the native bacterial community. These results suggest that spray drying can be successfully used to produce DC1-MCt microparticles to remediate molinate polluted sites through a bioaugmentation strategy. Graphical abstract: Highlights: Microencapsulation of mixed culture DC1 cells and molinate hydrolase using spray drier was successful. The molinate degrading activity of the microencapsulated biocatalysts was maintained after 6 months storage. Biocatalyst microparticles with modified chitosan were better than those with calcium alginate. Biocatalyst microparticles with modified chitosan removed environmental concentrations of molinate from river water. DC1 microparticles did not disturb the river indigenous bacterial community.