Biodegradation of poly(3-hydroxybutyrate), Sky-Green® and Mater-Bi® by fungi isolated from soils

In order to characterize the degradation behavior of three commercial biodegradable plastics, poly(3-hydroxybutyrate) (PHB), Sky-Green® (SG), a biodegradable aliphatic polyester made of succinic acid, adipic acid, butanediol and ethylene glycol, and Mater-Bi® (MB), a composite composed of starch based biodegradable polymers, were incubated in the forest soil, in the sandy soil, in the activated sludge soil, and in the farm soil at 28, 37, and 60°C, respectively. Seven PHB degrading fungi, five SG degrading fungi, and six MB degrading fungi were isolated by analyzing the microbiological characteristics of the fungi. Biodegradation of all three polymers was most active in the activated sludge soil. Both SG and MB showed higher degradability at 28°C than at 37°C. Biodegradability of PHB was highest at 37°C, while degradation of MB occurred reasonably well at 60°C. In the modified Sturm test Penicillium simplicissimum LAR 13 and Paecilomyces farinosus LAR 10 degraded PHB relatively well, while the degradation rate by Aspergillus fumigatus LAR 9 was lower than expected. P. simplicissimum LAR 13 showed the highest degradation rate for SG and A. fumigatus LAR 9 was most effective in degrading MB. Biodegradability of isolated fungi was affected by the incubation temperature. In both the soil burial test and the modified Sturm test the order of the biodegradation rate was PHB > SG > MB.