Optimization of polyethylene degradation by Zophobas atratus through a response-surface experimental design

Abstract

With the increasing levels of plastic pollution around the world the efforts to find sustainable solutions have redoubled. Some insects have the ability to degrade polyethylene foam (EPE); however, consumption levels have been low. Considering this, it is necessary to find conditions in which this process can be optimized. A Box-Behnken response surface experimental design was carried out to evaluate the EPE consumption process by Zophobas atratus larvae considering 3 factors: a) relative humidity (%HR), b) temperature and c) plastic particle size (TPP). Two response variables were evaluated: a) Specific degradation rate (TED) and b) survival rate. Each treatment lasted 28 days. All three factors showed significant direct effects (P<0.05) on the TED, in addition, factors A (temperature) and B (%HR) also had significant quadratic effects (P<0.05). For survival rate, it was found that factor A (temperature) and factor C (TPP) had significant quadratic effects (P<0.05). Numerical optimization showed a maximum theoretical TED of 2.67 mg EPE larva-1 day-1 under the following culture conditions: T=25°C, RH=53% and TPP=0.65in3. This experimental approach was able to significantly increase EPE consumption rates compared to previous preliminary studies carried out by our research group.