title: Formulations of polymeric biodegradable low-cost foam by melt extrusion to deliver plant growth-promoting bacteria in agricultural systems.
abstract: The extrusion technology of blends formed by compounds with different physicochemical properties often results in new materials that present properties distinctive from its original individual constituents. Here, we report the use of melt extrusion of blends made from low-cost materials to produce a biodegradable foam suitable for use as an inoculant carrier of plant growth-promoting bacteria (PGPB). Six formulations were prepared with variable proportions of the raw materials; the resulting physicochemical and structural properties are described, as well as formulation performance in the maintenance of bacterial viability during 120 days of storage. Differences in blend composition influenced foam density, porosity, expansion index, and water absorption. Additionally, differences in the capability of sustaining bacterial viability for long periods of time were more related to the foam composition than to the resulting physicochemical characteristics. Microscopic analyses showed that the inoculant bacteria had firmly attached to the extruded material by forming biofilms. Inoculation assays using maize plants demonstrated that the bacteria attached to the extruded foams could survive in the soil for up to 10 days before maize sowing, without diminishing its ability to promote plant growth. The results presented demonstrate the viability of the new matrix as a biotechnological material for bacterial delivery not only in agriculture but also in other biotechnological applications, according to the selected bacterial strains.
authors.affiliation: Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, Lorena, Brazil.
authors.forename: Paulo Ricardo Franco
authors.initials: PR
authors.lastname: Marcelino
authors.affiliation: Departamento de Bioquímica e Biotecnologia, Centro de Ciências Exatas, Universidade Estadual de Londrina, Londrina, Paraná, Brazil.
authors.forename: Karina Maria Lima
authors.initials: KM
authors.lastname: Milani
authors.affiliation: Departamento de Bioquímica e Biotecnologia, Centro de Ciências Exatas, Universidade Estadual de Londrina, Londrina, Paraná, Brazil.
authors.forename: Suzana
authors.initials: S
authors.lastname: Mali
authors.affiliation: Departamento de Agronomia, Centro de Ciências Agrárias, Universidade Estadual de Londrina, Londrina, Paraná, Brazil.
authors.forename: Odair José Andrade Pais Dos
authors.initials: OJ
authors.lastname: Santos
authors.affiliation: Departamento de Bioquímica e Biotecnologia, Centro de Ciências Exatas, Universidade Estadual de Londrina, Londrina, Paraná, Brazil. almoliva@uel.br.
authors.forename: André Luiz Martinez
authors.initials: AL
authors.lastname: de Oliveira
mesh_terms: D000383:Agriculture; D015806:Azospirillum brasilense / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D063245:Plant Development / Q000502:physiology*; D012988:Soil Microbiology; D003313:Zea mays / Q000254:growth & development* / Q000382:microbiology*
keywords: Azospirillum brasilense; Bacterial immobilization; Biocomposites; Inoculants