Elucidation of mechanical, physical, chemical and thermal properties of microbial composite films by integrating sodium alginate with Bacillus subtilis sp.

Abstract

Materials are the foundation in human development for improving human standards of life. This research aimed to develop microbial composite films by integrating sodium alginate with Bacillus subtilis. Sodium alginate film was fabricated as control. The microbial composite films were fabricated by integrating 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 g of Bacillus subtilis into the sodium alginate. Evaluations were performed on the mechanical, physical, chemical and thermal properties of the films. It was found that films reinforced with Bacillus subtilis significantly improved all the mentioned properties. Results show that 0.5 g microbial composite films had the highest tensile strength, breaking strain and toughness, which were 0.858 MPa, 87.406% and 0.045 MJ/m3, respectively. The thickness of the film was 1.057 mm. White light opacity, black light opacity and brightness values were 13.65%, 40.55% and 8.19%, respectively. It also had the highest conductivity, which was 37 mV, while its water absorption ability was 300.93%. Furthermore, it had a higher melting point of 218.94 °C and higher decomposition temperature of 252.69 °C. SEM also showed that it had filled cross-sectional structure and smoother surface compared to the sodium alginate film. Additionally, FTIR showed that 0.5 g microbial composite films possessed more functional groups at 800 and 662 cm-1 wavenumbers that referred to C–C, C–OH, C–H ring and side group vibrations and C-OH out-of-plane bending, respectively, which contributed to the stronger bonds in the microbial composite film. Initial conclusions depict the potential of Bacillus subtilis to be used as reinforcing material in the development of microbial composite films, which also have the prospect to be used in electronic applications. This is due to the conductivity of the films increasing as Bacillus subtilis cell mass in-creases.