Biodegradation Capacity and Activity Enzymatic of Bacillus subtilis against Low-Density Polyethylene
Ivana Ortega Rojas
Laboratorio de Micología Experimental, Facultad de Ciencias, Químicas, Universidad Autónoma de San Luis Potosí, S.L.P., México.
Adriana Rodríguez Pérez
Unidad Académica Multidisciplinaria, Zona Media, Universidad Autónoma de San Luis Potosí, S.L.P., México.
Juan Fernando Cárdenas González
Unidad Académica Multidisciplinaria, Zona Media, Universidad Autónoma de San Luis Potosí, S.L.P., México.
Víctor Manuel Martínez Juárez
Instituto de Ciencias Agropecuarias, Área Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de Hidalgo, Tulancingo de Bravo, México.
Erika Enriquez Domínguez
Laboratorio de Micología Experimental, Facultad de Ciencias, Químicas, Universidad Autónoma de San Luis Potosí, S.L.P., México.
Juana Tovar Oviedo
Laboratorio de Micología Experimental, Facultad de Ciencias, Químicas, Universidad Autónoma de San Luis Potosí, S.L.P., México.
Ismael Acosta Rodríguez *
Laboratorio de Micología Experimental, Facultad de Ciencias, Químicas, Universidad Autónoma de San Luis Potosí, S.L.P., México.
*Author to whom correspondence should be addressed.
Abstract
Aims: The objective of this work was to determine the degradation capacity of low-density polyethylene by the bacterium Bacillus subtilis and analyze the production of extracellular laccase activity.
Methodology: The experiments was realized in 50 mL of culture medium, added with a fragment of known dry weight (1 cm2 colorless polyethylene bag squares), and were incubated at 28°C, pH 6.5, for 6 months under static conditions, determining the growth of the bacterium by dry weight (68, 75, and 91 mg), the production of extracellular protein (271, 234, and 326.1 mg/mL), and the degradation of the substrate by dry biodegraded (8.57%, 5.88%, and 11.76%).
Results: The production of extracellular laccase enzyme was analyzed in presence of polyethylene, finding an enzymatic activity of laccase of 2.06, 1.49, and 2,03 U/mL, while in the control without substrate, no enzymatic activity was observed, which suggests that this enzyme may participate in the degradation of polyethylene. In addition, some characteristics of the extracellular enzymatic activities were analyzed, such as stability at 4oC and 28oC, optimal pH and temperature, the effect of protein and substrate concentration.
Conclusion: The extracellular protein production and dry weight of the bacterium are higher in the presence of low-density polyethylene. The laccase activity is very stable at 4oC and 28oC, the most effective pH and temperature, were 4.5 and 28oC, and present an incubation time of 5 minutes, and this data suggest that this enzymatic activitiy may participate in the degradation of low density polyethylene.
Keywords: Bacillus subtilis, polyethylene, biodegradation, extracellular laccases